1 /*
   2  * Copyright (c) 1999, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.util.regex;
  27 
  28 import java.text.Normalizer;
  29 import java.text.Normalizer.Form;
  30 import java.util.Locale;
  31 import java.util.Iterator;
  32 import java.util.Map;
  33 import java.util.ArrayList;
  34 import java.util.HashMap;
  35 import java.util.LinkedHashSet;
  36 import java.util.List;
  37 import java.util.Set;
  38 import java.util.Arrays;
  39 import java.util.NoSuchElementException;
  40 import java.util.Spliterator;
  41 import java.util.Spliterators;
  42 import java.util.function.Predicate;
  43 import java.util.stream.Stream;
  44 import java.util.stream.StreamSupport;
  45 
  46 
  47 /**
  48  * A compiled representation of a regular expression.
  49  *
  50  * <p> A regular expression, specified as a string, must first be compiled into
  51  * an instance of this class.  The resulting pattern can then be used to create
  52  * a {@link Matcher} object that can match arbitrary {@linkplain
  53  * java.lang.CharSequence character sequences} against the regular
  54  * expression.  All of the state involved in performing a match resides in the
  55  * matcher, so many matchers can share the same pattern.
  56  *
  57  * <p> A typical invocation sequence is thus
  58  *
  59  * <blockquote><pre>
  60  * Pattern p = Pattern.{@link #compile compile}("a*b");
  61  * Matcher m = p.{@link #matcher matcher}("aaaaab");
  62  * boolean b = m.{@link Matcher#matches matches}();</pre></blockquote>
  63  *
  64  * <p> A {@link #matches matches} method is defined by this class as a
  65  * convenience for when a regular expression is used just once.  This method
  66  * compiles an expression and matches an input sequence against it in a single
  67  * invocation.  The statement
  68  *
  69  * <blockquote><pre>
  70  * boolean b = Pattern.matches("a*b", "aaaaab");</pre></blockquote>
  71  *
  72  * is equivalent to the three statements above, though for repeated matches it
  73  * is less efficient since it does not allow the compiled pattern to be reused.
  74  *
  75  * <p> Instances of this class are immutable and are safe for use by multiple
  76  * concurrent threads.  Instances of the {@link Matcher} class are not safe for
  77  * such use.
  78  *
  79  *
  80  * <h3><a id="sum">Summary of regular-expression constructs</a></h3>
  81  *
  82  * <table class="borderless">
  83  * <caption style="display:none">Regular expression constructs, and what they match</caption>
  84  * <thead style="text-align:left">
  85  * <tr>
  86  * <th id="construct">Construct</th>
  87  * <th id="matches">Matches</th>
  88  * </tr>
  89  * </thead>
  90  * <tbody style="text-align:left">
  91  *
  92  * <tr><th colspan="2" style="padding-top:20px" id="characters">Characters</th></tr>
  93  *
  94  * <tr><th style="vertical-align:top; font-weight: normal" id="x"><i>x</i></th>
  95  *     <td headers="matches characters x">The character <i>x</i></td></tr>
  96  * <tr><th style="vertical-align:top; font-weight: normal" id="backslash">{@code \\}</th>
  97  *     <td headers="matches characters backslash">The backslash character</td></tr>
  98  * <tr><th style="vertical-align:top; font-weight: normal" id="octal_n">{@code \0}<i>n</i></th>
  99  *     <td headers="matches characters octal_n">The character with octal value {@code 0}<i>n</i>
 100  *         (0&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;7)</td></tr>
 101  * <tr><th style="vertical-align:top; font-weight: normal" id="octal_nn">{@code \0}<i>nn</i></th>
 102  *     <td headers="matches characters octal_nn">The character with octal value {@code 0}<i>nn</i>
 103  *         (0&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;7)</td></tr>
 104  * <tr><th style="vertical-align:top; font-weight: normal" id="octal_nnn">{@code \0}<i>mnn</i></th>
 105  *     <td headers="matches characters octal_nnn">The character with octal value {@code 0}<i>mnn</i>
 106  *         (0&nbsp;{@code <=}&nbsp;<i>m</i>&nbsp;{@code <=}&nbsp;3,
 107  *         0&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;7)</td></tr>
 108  * <tr><th style="vertical-align:top; font-weight: normal" id="hex_hh">{@code \x}<i>hh</i></th>
 109  *     <td headers="matches characters hex_hh">The character with hexadecimal value {@code 0x}<i>hh</i></td></tr>
 110  * <tr><th style="vertical-align:top; font-weight: normal" id="hex_hhhh"><code>\u</code><i>hhhh</i></th>
 111  *     <td headers="matches characters hex_hhhh">The character with hexadecimal&nbsp;value&nbsp;{@code 0x}<i>hhhh</i></td></tr>
 112  * <tr><th style="vertical-align:top; font-weight: normal" id="hex_h_h"><code>\x</code><i>{h...h}</i></th>
 113  *     <td headers="matches characters hex_h_h">The character with hexadecimal value {@code 0x}<i>h...h</i>
 114  *         ({@link java.lang.Character#MIN_CODE_POINT Character.MIN_CODE_POINT}
 115  *         &nbsp;&lt;=&nbsp;{@code 0x}<i>h...h</i>&nbsp;&lt;=&nbsp;
 116  *          {@link java.lang.Character#MAX_CODE_POINT Character.MAX_CODE_POINT})</td></tr>
 117  * <tr><th style="vertical-align:top; font-weight: normal" id="unicode_name"><code>\N{</code><i>name</i><code>}</code></th>
 118  *     <td headers="matches characters unicode_name">The character with Unicode character name <i>'name'</i></td></tr>
 119  * <tr><th style="vertical-align:top; font-weight:normal" id="tab">{@code \t}</th>
 120  *     <td headers="matches characters tab">The tab character (<code>'\u0009'</code>)</td></tr>
 121  * <tr><th style="vertical-align:top; font-weight:normal" id="newline">{@code \n}</th>
 122  *     <td headers="matches characters newline">The newline (line feed) character (<code>'\u000A'</code>)</td></tr>
 123  * <tr><th style="vertical-align:top; font-weight:normal" id="return">{@code \r}</th>
 124  *     <td headers="matches characters return">The carriage-return character (<code>'\u000D'</code>)</td></tr>
 125  * <tr><th style="vertical-align:top; font-weight:normal" id="form_feed">{@code \f}</th>
 126  *     <td headers="matches characters form_feed">The form-feed character (<code>'\u000C'</code>)</td></tr>
 127  * <tr><th style="vertical-align:top; font-weight:normal" id="bell">{@code \a}</th>
 128  *     <td headers="matches characters bell">The alert (bell) character (<code>'\u0007'</code>)</td></tr>
 129  * <tr><th style="vertical-align:top; font-weight:normal" id="escape">{@code \e}</th>
 130  *     <td headers="matches characters escape">The escape character (<code>'\u001B'</code>)</td></tr>
 131  * <tr><th style="vertical-align:top; font-weight:normal" id="ctrl_x">{@code \c}<i>x</i></th>
 132  *     <td headers="matches characters ctrl_x">The control character corresponding to <i>x</i></td></tr>
 133  *
 134  *  <tr><th colspan="2" style="padding-top:20px" id="classes">Character classes</th></tr>
 135  *
 136  * <tr><th style="vertical-align:top; font-weight:normal" id="simple">{@code [abc]}</th>
 137  *     <td headers="matches classes simple">{@code a}, {@code b}, or {@code c} (simple class)</td></tr>
 138  * <tr><th style="vertical-align:top; font-weight:normal" id="negation">{@code [^abc]}</th>
 139  *     <td headers="matches classes negation">Any character except {@code a}, {@code b}, or {@code c} (negation)</td></tr>
 140  * <tr><th style="vertical-align:top; font-weight:normal" id="range">{@code [a-zA-Z]}</th>
 141  *     <td headers="matches classes range">{@code a} through {@code z}
 142  *         or {@code A} through {@code Z}, inclusive (range)</td></tr>
 143  * <tr><th style="vertical-align:top; font-weight:normal" id="union">{@code [a-d[m-p]]}</th>
 144  *     <td headers="matches classes union">{@code a} through {@code d},
 145  *      or {@code m} through {@code p}: {@code [a-dm-p]} (union)</td></tr>
 146  * <tr><th style="vertical-align:top; font-weight:normal" id="intersection">{@code [a-z&&[def]]}</th>
 147  *     <td headers="matches classes intersection">{@code d}, {@code e}, or {@code f} (intersection)</tr>
 148  * <tr><th style="vertical-align:top; font-weight:normal" id="subtraction1">{@code [a-z&&[^bc]]}</th>
 149  *     <td headers="matches classes subtraction1">{@code a} through {@code z},
 150  *         except for {@code b} and {@code c}: {@code [ad-z]} (subtraction)</td></tr>
 151  * <tr><th style="vertical-align:top; font-weight:normal" id="subtraction2">{@code [a-z&&[^m-p]]}</th>
 152  *     <td headers="matches classes subtraction2">{@code a} through {@code z},
 153  *          and not {@code m} through {@code p}: {@code [a-lq-z]}(subtraction)</td></tr>
 154  *
 155  * <tr><th colspan="2" style="padding-top:20px" id="predef">Predefined character classes</th></tr>
 156  *
 157  * <tr><th style="vertical-align:top; font-weight:normal" id="any">{@code .}</th>
 158  *     <td headers="matches predef any">Any character (may or may not match <a href="#lt">line terminators</a>)</td></tr>
 159  * <tr><th style="vertical-align:top; font-weight:normal" id="digit">{@code \d}</th>
 160  *     <td headers="matches predef digit">A digit: {@code [0-9]}</td></tr>
 161  * <tr><th style="vertical-align:top; font-weight:normal" id="non_digit">{@code \D}</th>
 162  *     <td headers="matches predef non_digit">A non-digit: {@code [^0-9]}</td></tr>
 163  * <tr><th style="vertical-align:top; font-weight:normal" id="horiz_white">{@code \h}</th>
 164  *     <td headers="matches predef horiz_white">A horizontal whitespace character:
 165  *     <code>[ \t\xA0\u1680\u180e\u2000-\u200a\u202f\u205f\u3000]</code></td></tr>
 166  * <tr><th style="vertical-align:top; font-weight:normal" id="non_horiz_white">{@code \H}</th>
 167  *     <td headers="matches predef non_horiz_white">A non-horizontal whitespace character: {@code [^\h]}</td></tr>
 168  * <tr><th style="vertical-align:top; font-weight:normal" id="white">{@code \s}</th>
 169  *     <td headers="matches predef white">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
 170  * <tr><th style="vertical-align:top; font-weight:normal" id="non_white">{@code \S}</th>
 171  *     <td headers="matches predef non_white">A non-whitespace character: {@code [^\s]}</td></tr>
 172  * <tr><th style="vertical-align:top; font-weight:normal" id="vert_white">{@code \v}</th>
 173  *     <td headers="matches predef vert_white">A vertical whitespace character: <code>[\n\x0B\f\r\x85\u2028\u2029]</code>
 174  *     </td></tr>
 175  * <tr><th style="vertical-align:top; font-weight:normal" id="non_vert_white">{@code \V}</th>
 176  *     <td headers="matches predef non_vert_white">A non-vertical whitespace character: {@code [^\v]}</td></tr>
 177  * <tr><th style="vertical-align:top; font-weight:normal" id="word">{@code \w}</th>
 178  *     <td headers="matches predef word">A word character: {@code [a-zA-Z_0-9]}</td></tr>
 179  * <tr><th style="vertical-align:top; font-weight:normal" id="non_word">{@code \W}</th>
 180  *     <td headers="matches predef non_word">A non-word character: {@code [^\w]}</td></tr>
 181  *
 182  * <tr><th colspan="2" style="padding-top:20px" id="posix"><b>POSIX character classes (US-ASCII only)</b></th></tr>
 183  *
 184  * <tr><th style="vertical-align:top; font-weight:normal" id="Lower">{@code \p{Lower}}</th>
 185  *     <td headers="matches posix Lower">A lower-case alphabetic character: {@code [a-z]}</td></tr>
 186  * <tr><th style="vertical-align:top; font-weight:normal" id="Upper">{@code \p{Upper}}</th>
 187  *     <td headers="matches posix Upper">An upper-case alphabetic character:{@code [A-Z]}</td></tr>
 188  * <tr><th style="vertical-align:top; font-weight:normal" id="ASCII">{@code \p{ASCII}}</th>
 189  *     <td headers="matches posix ASCII">All ASCII:{@code [\x00-\x7F]}</td></tr>
 190  * <tr><th style="vertical-align:top; font-weight:normal" id="Alpha">{@code \p{Alpha}}</th>
 191  *     <td headers="matches posix Alpha">An alphabetic character:{@code [\p{Lower}\p{Upper}]}</td></tr>
 192  * <tr><th style="vertical-align:top; font-weight:normal" id="Digit">{@code \p{Digit}}</th>
 193  *     <td headers="matches posix Digit">A decimal digit: {@code [0-9]}</td></tr>
 194  * <tr><th style="vertical-align:top; font-weight:normal" id="Alnum">{@code \p{Alnum}}</th>
 195  *     <td headers="matches posix Alnum">An alphanumeric character:{@code [\p{Alpha}\p{Digit}]}</td></tr>
 196  * <tr><th style="vertical-align:top; font-weight:normal" id="Punct">{@code \p{Punct}}</th>
 197  *     <td headers="matches posix Punct">Punctuation: One of {@code !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~}</td></tr>
 198  *     <!-- {@code [\!"#\$%&'\(\)\*\+,\-\./:;\<=\>\?@\[\\\]\^_`\{\|\}~]}
 199  *          {@code [\X21-\X2F\X31-\X40\X5B-\X60\X7B-\X7E]} -->
 200  * <tr><th style="vertical-align:top; font-weight:normal" id="Graph">{@code \p{Graph}}</th>
 201  *     <td headers="matches posix Graph">A visible character: {@code [\p{Alnum}\p{Punct}]}</td></tr>
 202  * <tr><th style="vertical-align:top; font-weight:normal" id="Print">{@code \p{Print}}</th>
 203  *     <td headers="matches posix Print">A printable character: {@code [\p{Graph}\x20]}</td></tr>
 204  * <tr><th style="vertical-align:top; font-weight:normal" id="Blank">{@code \p{Blank}}</th>
 205  *     <td headers="matches posix Blank">A space or a tab: {@code [ \t]}</td></tr>
 206  * <tr><th style="vertical-align:top; font-weight:normal" id="Cntrl">{@code \p{Cntrl}}</th>
 207  *     <td headers="matches posix Cntrl">A control character: {@code [\x00-\x1F\x7F]}</td></tr>
 208  * <tr><th style="vertical-align:top; font-weight:normal" id="XDigit">{@code \p{XDigit}}</th>
 209  *     <td headers="matches posix XDigit">A hexadecimal digit: {@code [0-9a-fA-F]}</td></tr>
 210  * <tr><th style="vertical-align:top; font-weight:normal" id="Space">{@code \p{Space}}</th>
 211  *     <td headers="matches posix Space">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
 212  *
 213  * <tr><th colspan="2" style="padding-top:20px" id="java">java.lang.Character classes (simple <a href="#jcc">java character type</a>)</th></tr>
 214  *
 215  * <tr><th style="vertical-align:top; font-weight:normal" id="javaLowerCase">{@code \p{javaLowerCase}}</th>
 216  *     <td headers="matches java javaLowerCase">Equivalent to java.lang.Character.isLowerCase()</td></tr>
 217  * <tr><th style="vertical-align:top; font-weight:normal" id="javaUpperCase">{@code \p{javaUpperCase}}</th>
 218  *     <td headers="matches java javaUpperCase">Equivalent to java.lang.Character.isUpperCase()</td></tr>
 219  * <tr><th style="vertical-align:top; font-weight:normal" id="javaWhitespace">{@code \p{javaWhitespace}}</th>
 220  *     <td headers="matches java javaWhitespace">Equivalent to java.lang.Character.isWhitespace()</td></tr>
 221  * <tr><th style="vertical-align:top; font-weight:normal" id="javaMirrored">{@code \p{javaMirrored}}</th>
 222  *     <td headers="matches java javaMirrored">Equivalent to java.lang.Character.isMirrored()</td></tr>
 223  *
 224  * <tr><th colspan="2" style="padding-top:20px"  id="unicode">Classes for Unicode scripts, blocks, categories and binary properties</th></tr>
 225  *
 226  * <tr><th style="vertical-align:top; font-weight:normal" id="IsLatin">{@code \p{IsLatin}}</th>
 227  *     <td headers="matches unicode IsLatin">A Latin&nbsp;script character (<a href="#usc">script</a>)</td></tr>
 228  * <tr><th style="vertical-align:top; font-weight:normal" id="InGreek">{@code \p{InGreek}}</th>
 229  *     <td headers="matches unicode InGreek">A character in the Greek&nbsp;block (<a href="#ubc">block</a>)</td></tr>
 230  * <tr><th style="vertical-align:top; font-weight:normal" id="Lu">{@code \p{Lu}}</th>
 231  *     <td headers="matches unicode Lu">An uppercase letter (<a href="#ucc">category</a>)</td></tr>
 232  * <tr><th style="vertical-align:top; font-weight:normal" id="IsAlphabetic">{@code \p{IsAlphabetic}}</th>
 233  *     <td headers="matches unicode IsAlphabetic">An alphabetic character (<a href="#ubpc">binary property</a>)</td></tr>
 234  * <tr><th style="vertical-align:top; font-weight:normal" id="Sc">{@code \p{Sc}}</th>
 235  *     <td headers="matches unicode Sc">A currency symbol</td></tr>
 236  * <tr><th style="vertical-align:top; font-weight:normal" id="not_InGreek">{@code \P{InGreek}}</th>
 237  *     <td headers="matches unicode not_InGreek">Any character except one in the Greek block (negation)</td></tr>
 238  * <tr><th style="vertical-align:top; font-weight:normal" id="not_uppercase">{@code [\p{L}&&[^\p{Lu}]]}</th>
 239  *     <td headers="matches unicode not_uppercase">Any letter except an uppercase letter (subtraction)</td></tr>
 240  *
 241  * <tr><th colspan="2" style="padding-top:20px" id="bounds">Boundary matchers</th></tr>
 242  *
 243  * <tr><th style="vertical-align:top; font-weight:normal" id="begin_line">{@code ^}</th>
 244  *     <td headers="matches bounds begin_line">The beginning of a line</td></tr>
 245  * <tr><th style="vertical-align:top; font-weight:normal" id="end_line">{@code $}</th>
 246  *     <td headers="matches bounds end_line">The end of a line</td></tr>
 247  * <tr><th style="vertical-align:top; font-weight:normal" id="word_boundary">{@code \b}</th>
 248  *     <td headers="matches bounds word_boundary">A word boundary</td></tr>
 249  * <tr><th style="vertical-align:top; font-weight:normal" id="grapheme_cluster_boundary">{@code \b{g}}</th>
 250  *     <td headers="matches bounds grapheme_cluster_boundary">A Unicode extended grapheme cluster boundary</td></tr>
 251  * <tr><th style="vertical-align:top; font-weight:normal" id="non_word_boundary">{@code \B}</th>
 252  *     <td headers="matches bounds non_word_boundary">A non-word boundary</td></tr>
 253  * <tr><th style="vertical-align:top; font-weight:normal" id="begin_input">{@code \A}</th>
 254  *     <td headers="matches bounds begin_input">The beginning of the input</td></tr>
 255  * <tr><th style="vertical-align:top; font-weight:normal" id="end_prev_match">{@code \G}</th>
 256  *     <td headers="matches bounds end_prev_match">The end of the previous match</td></tr>
 257  * <tr><th style="vertical-align:top; font-weight:normal" id="end_input_except_term">{@code \Z}</th>
 258  *     <td headers="matches bounds end_input_except_term">The end of the input but for the final
 259  *         <a href="#lt">terminator</a>, if&nbsp;any</td></tr>
 260  * <tr><th style="vertical-align:top; font-weight:normal" id="end_input">{@code \z}</th>
 261  *     <td headers="matches bounds end_input">The end of the input</td></tr>
 262  *
 263  * <tr><th colspan="2" style="padding-top:20px" id="linebreak">Linebreak matcher</th></tr>
 264  *
 265  * <tr><th style="vertical-align:top; font-weight:normal" id="any_unicode_linebreak">{@code \R}</th>
 266  *     <td headers="matches linebreak any_unicode_linebreak">Any Unicode linebreak sequence, is equivalent to
 267  *     <code>\u000D\u000A|[\u000A\u000B\u000C\u000D\u0085\u2028\u2029]
 268  *     </code></td></tr>
 269  *
 270  * <tr><th colspan="2" style="padding-top:20px" id="grapheme">Unicode Extended Grapheme matcher</th></tr>
 271  *
 272  * <tr><th style="vertical-align:top; font-weight:normal" id="grapheme_any">{@code \X}</th>
 273  *     <td headers="matches grapheme grapheme_any">Any Unicode extended grapheme cluster</td></tr>
 274  *
 275  * <tr><th colspan="2" style="padding-top:20px" id="greedy">Greedy quantifiers</th></tr>
 276  *
 277  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_once_or_not"><i>X</i>{@code ?}</th>
 278  *     <td headers="matches greedy greedy_once_or_not"><i>X</i>, once or not at all</td></tr>
 279  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_zero_or_more"><i>X</i>{@code *}</th>
 280  *     <td headers="matches greedy greedy_zero_or_more"><i>X</i>, zero or more times</td></tr>
 281  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_one_or_more"><i>X</i>{@code +}</th>
 282  *     <td headers="matches greedy greedy_one_or_more"><i>X</i>, one or more times</td></tr>
 283  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_exactly"><i>X</i><code>{</code><i>n</i><code>}</code></th>
 284  *     <td headers="matches greedy greedy_exactly"><i>X</i>, exactly <i>n</i> times</td></tr>
 285  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_at_least"><i>X</i><code>{</code><i>n</i>{@code ,}}</th>
 286  *     <td headers="matches greedy greedy_at_least"><i>X</i>, at least <i>n</i> times</td></tr>
 287  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_at_least_up_to"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}</code></th>
 288  *     <td headers="matches greedy greedy_at_least_up_to"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
 289  *
 290  * <tr><th colspan="2" style="padding-top:20px" id="reluc">Reluctant quantifiers</th></tr>
 291  *
 292  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_once_or_not"><i>X</i>{@code ??}</th>
 293  *     <td headers="matches reluc reluc_once_or_not"><i>X</i>, once or not at all</td></tr>
 294  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_zero_or_more"><i>X</i>{@code *?}</th>
 295  *     <td headers="matches reluc reluc_zero_or_more"><i>X</i>, zero or more times</td></tr>
 296  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_one_or_more"><i>X</i>{@code +?}</th>
 297  *     <td headers="matches reluc reluc_one_or_more"><i>X</i>, one or more times</td></tr>
 298  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_exactly"><i>X</i><code>{</code><i>n</i><code>}?</code></th>
 299  *     <td headers="matches reluc reluc_exactly"><i>X</i>, exactly <i>n</i> times</td></tr>
 300  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_at_least"><i>X</i><code>{</code><i>n</i><code>,}?</code></th>
 301  *     <td headers="matches reluc reluc_at_least"><i>X</i>, at least <i>n</i> times</td></tr>
 302  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_at_least_up_to"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}?</code></th>
 303  *     <td headers="matches reluc reluc_at_least_up_to"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
 304  *
 305  * <tr><th colspan="2" style="padding-top:20px" id="poss">Possessive quantifiers</th></tr>
 306  *
 307  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_once_or_not"><i>X</i>{@code ?+}</th>
 308  *     <td headers="matches poss poss_once_or_not"><i>X</i>, once or not at all</td></tr>
 309  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_zero_or_more"><i>X</i>{@code *+}</th>
 310  *     <td headers="matches poss poss_zero_or_more"><i>X</i>, zero or more times</td></tr>
 311  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_one_or_more"><i>X</i>{@code ++}</th>
 312  *     <td headers="matches poss poss_one_or_more"><i>X</i>, one or more times</td></tr>
 313  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_exactly"><i>X</i><code>{</code><i>n</i><code>}+</code></th>
 314  *     <td headers="matches poss poss_exactly"><i>X</i>, exactly <i>n</i> times</td></tr>
 315  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_at_least"><i>X</i><code>{</code><i>n</i><code>,}+</code></th>
 316  *     <td headers="matches poss poss_at_least"><i>X</i>, at least <i>n</i> times</td></tr>
 317  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_at_least_up_to"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}+</code></th>
 318  *     <td headers="matches poss poss_at_least_up_to"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
 319  *
 320  * <tr><th colspan="2" style="padding-top:20px" id="logical">Logical operators</th></tr>
 321  *
 322  * <tr><th style="vertical-align:top; font-weight:normal" id="concat"><i>XY</i></th>
 323  *     <td headers="matches logical concat"><i>X</i> followed by <i>Y</i></td></tr>
 324  * <tr><th style="vertical-align:top; font-weight:normal" id="alternate"><i>X</i>{@code |}<i>Y</i></th>
 325  *     <td headers="matches logical alternate">Either <i>X</i> or <i>Y</i></td></tr>
 326  * <tr><th style="vertical-align:top; font-weight:normal" id="group">{@code (}<i>X</i>{@code )}</th>
 327  *     <td headers="matches logical group">X, as a <a href="#cg">capturing group</a></td></tr>
 328  *
 329  * <tr><th colspan="2" style="padding-top:20px" id="backref">Back references</th></tr>
 330  *
 331  * <tr><th style="vertical-align:top; font-weight:normal" id="back_nth">{@code \}<i>n</i></th>
 332  *     <td headers="matches backref back_nth">Whatever the <i>n</i><sup>th</sup>
 333  *     <a href="#cg">capturing group</a> matched</td></tr>
 334  * <tr><th style="vertical-align:top; font-weight:normal" id="back_named">{@code \}<i>k</i>&lt;<i>name</i>&gt;</th>
 335  *     <td headers="matches backref back_named">Whatever the
 336  *     <a href="#groupname">named-capturing group</a> "name" matched</td></tr>
 337  *
 338  * <tr><th colspan="2" style="padding-top:20px" id="quote">Quotation</th></tr>
 339  *
 340  * <tr><th style="vertical-align:top; font-weight:normal" id="quote_follow">{@code \}</th>
 341  *     <td headers="matches quote quote_follow">Nothing, but quotes the following character</td></tr>
 342  * <tr><th style="vertical-align:top; font-weight:normal" id="quote_begin">{@code \Q}</th>
 343  *     <td headers="matches quote quote_begin">Nothing, but quotes all characters until {@code \E}</td></tr>
 344  * <tr><th style="vertical-align:top; font-weight:normal" id="quote_end">{@code \E}</th>
 345  *     <td headers="matches quote quote_end">Nothing, but ends quoting started by {@code \Q}</td></tr>
 346  *     <!-- Metachars: !$()*+.<>?[\]^{|} -->
 347  *
 348  * <tr><th colspan="2" style="padding-top:20px" id="special">Special constructs (named-capturing and non-capturing)</th></tr>
 349  *
 350  * <tr><th style="vertical-align:top; font-weight:normal" id="named_group"><code>(?&lt;<a href="#groupname">name</a>&gt;</code><i>X</i>{@code )}</th>
 351  *     <td headers="matches special named_group"><i>X</i>, as a named-capturing group</td></tr>
 352  * <tr><th style="vertical-align:top; font-weight:normal" id="non_capture_group">{@code (?:}<i>X</i>{@code )}</th>
 353  *     <td headers="matches special non_capture_group"><i>X</i>, as a non-capturing group</td></tr>
 354  * <tr><th style="vertical-align:top; font-weight:normal" id="flags"><code>(?idmsuxU-idmsuxU)&nbsp;</code></th>
 355  *     <td headers="matches special flags">Nothing, but turns match flags <a href="#CASE_INSENSITIVE">i</a>
 356  * <a href="#UNIX_LINES">d</a> <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a>
 357  * <a href="#UNICODE_CASE">u</a> <a href="#COMMENTS">x</a> <a href="#UNICODE_CHARACTER_CLASS">U</a>
 358  * on - off</td></tr>
 359  * <tr><th style="vertical-align:top; font-weight:normal" id="non_capture_group_flags"><code>(?idmsux-idmsux:</code><i>X</i>{@code )}&nbsp;&nbsp;</th>
 360  *     <td headers="matches special non_capture_group_flags"><i>X</i>, as a <a href="#cg">non-capturing group</a> with the
 361  *         given flags <a href="#CASE_INSENSITIVE">i</a> <a href="#UNIX_LINES">d</a>
 362  * <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a> <a href="#UNICODE_CASE">u</a >
 363  * <a href="#COMMENTS">x</a> on - off</td></tr>
 364  * <tr><th style="vertical-align:top; font-weight:normal" id="pos_lookahead">{@code (?=}<i>X</i>{@code )}</th>
 365  *     <td headers="matches special pos_lookahead"><i>X</i>, via zero-width positive lookahead</td></tr>
 366  * <tr><th style="vertical-align:top; font-weight:normal" id="neg_lookahead">{@code (?!}<i>X</i>{@code )}</th>
 367  *     <td headers="matches special neg_lookahead"><i>X</i>, via zero-width negative lookahead</td></tr>
 368  * <tr><th style="vertical-align:top; font-weight:normal" id="pos_lookbehind">{@code (?<=}<i>X</i>{@code )}</th>
 369  *     <td headers="matches special pos_lookbehind"><i>X</i>, via zero-width positive lookbehind</td></tr>
 370  * <tr><th style="vertical-align:top; font-weight:normal" id="neg_lookbehind">{@code (?<!}<i>X</i>{@code )}</th>
 371  *     <td headers="matches special neg_lookbehind"><i>X</i>, via zero-width negative lookbehind</td></tr>
 372  * <tr><th style="vertical-align:top; font-weight:normal" id="indep_non_capture_group">{@code (?>}<i>X</i>{@code )}</th>
 373  *     <td headers="matches special indep_non_capture_group"><i>X</i>, as an independent, non-capturing group</td></tr>
 374  *
 375  * </tbody>
 376  * </table>
 377  *
 378  * <hr>
 379  *
 380  *
 381  * <h3><a id="bs">Backslashes, escapes, and quoting</a></h3>
 382  *
 383  * <p> The backslash character ({@code '\'}) serves to introduce escaped
 384  * constructs, as defined in the table above, as well as to quote characters
 385  * that otherwise would be interpreted as unescaped constructs.  Thus the
 386  * expression {@code \\} matches a single backslash and <code>\{</code> matches a
 387  * left brace.
 388  *
 389  * <p> It is an error to use a backslash prior to any alphabetic character that
 390  * does not denote an escaped construct; these are reserved for future
 391  * extensions to the regular-expression language.  A backslash may be used
 392  * prior to a non-alphabetic character regardless of whether that character is
 393  * part of an unescaped construct.
 394  *
 395  * <p> Backslashes within string literals in Java source code are interpreted
 396  * as required by
 397  * <cite>The Java&trade; Language Specification</cite>
 398  * as either Unicode escapes (section 3.3) or other character escapes (section 3.10.6)
 399  * It is therefore necessary to double backslashes in string
 400  * literals that represent regular expressions to protect them from
 401  * interpretation by the Java bytecode compiler.  The string literal
 402  * <code>"\b"</code>, for example, matches a single backspace character when
 403  * interpreted as a regular expression, while {@code "\\b"} matches a
 404  * word boundary.  The string literal {@code "\(hello\)"} is illegal
 405  * and leads to a compile-time error; in order to match the string
 406  * {@code (hello)} the string literal {@code "\\(hello\\)"}
 407  * must be used.
 408  *
 409  * <h3><a id="cc">Character Classes</a></h3>
 410  *
 411  *    <p> Character classes may appear within other character classes, and
 412  *    may be composed by the union operator (implicit) and the intersection
 413  *    operator ({@code &&}).
 414  *    The union operator denotes a class that contains every character that is
 415  *    in at least one of its operand classes.  The intersection operator
 416  *    denotes a class that contains every character that is in both of its
 417  *    operand classes.
 418  *
 419  *    <p> The precedence of character-class operators is as follows, from
 420  *    highest to lowest:
 421  *
 422  *    <table class="striped" style="margin-left: 2em;">
 423  *      <caption style="display:none">Precedence of character class operators.</caption>
 424  *      <thead>
 425  *      <tr><th scope="col">Precedence<th scope="col">Name<th scope="col">Example
 426  *      </thead>
 427  *      <tbody>
 428  *      <tr><th scope="row">1</th>
 429  *        <td>Literal escape&nbsp;&nbsp;&nbsp;&nbsp;</td>
 430  *        <td>{@code \x}</td></tr>
 431  *     <tr><th scope="row">2</th>
 432  *        <td>Grouping</td>
 433  *        <td>{@code [...]}</td></tr>
 434  *     <tr><th scope="row">3</th>
 435  *        <td>Range</td>
 436  *        <td>{@code a-z}</td></tr>
 437  *      <tr><th scope="row">4</th>
 438  *        <td>Union</td>
 439  *        <td>{@code [a-e][i-u]}</td></tr>
 440  *      <tr><th scope="row">5</th>
 441  *        <td>Intersection</td>
 442  *        <td>{@code [a-z&&[aeiou]]}</td></tr>
 443  *      </tbody>
 444  *    </table>
 445  *
 446  *    <p> Note that a different set of metacharacters are in effect inside
 447  *    a character class than outside a character class. For instance, the
 448  *    regular expression {@code .} loses its special meaning inside a
 449  *    character class, while the expression {@code -} becomes a range
 450  *    forming metacharacter.
 451  *
 452  * <h3><a id="lt">Line terminators</a></h3>
 453  *
 454  * <p> A <i>line terminator</i> is a one- or two-character sequence that marks
 455  * the end of a line of the input character sequence.  The following are
 456  * recognized as line terminators:
 457  *
 458  * <ul>
 459  *
 460  *   <li> A newline (line feed) character ({@code '\n'}),
 461  *
 462  *   <li> A carriage-return character followed immediately by a newline
 463  *   character ({@code "\r\n"}),
 464  *
 465  *   <li> A standalone carriage-return character ({@code '\r'}),
 466  *
 467  *   <li> A next-line character (<code>'\u0085'</code>),
 468  *
 469  *   <li> A line-separator character (<code>'\u2028'</code>), or
 470  *
 471  *   <li> A paragraph-separator character (<code>'\u2029'</code>).
 472  *
 473  * </ul>
 474  * <p>If {@link #UNIX_LINES} mode is activated, then the only line terminators
 475  * recognized are newline characters.
 476  *
 477  * <p> The regular expression {@code .} matches any character except a line
 478  * terminator unless the {@link #DOTALL} flag is specified.
 479  *
 480  * <p> By default, the regular expressions {@code ^} and {@code $} ignore
 481  * line terminators and only match at the beginning and the end, respectively,
 482  * of the entire input sequence. If {@link #MULTILINE} mode is activated then
 483  * {@code ^} matches at the beginning of input and after any line terminator
 484  * except at the end of input. When in {@link #MULTILINE} mode {@code $}
 485  * matches just before a line terminator or the end of the input sequence.
 486  *
 487  * <h3><a id="cg">Groups and capturing</a></h3>
 488  *
 489  * <h4><a id="gnumber">Group number</a></h4>
 490  * <p> Capturing groups are numbered by counting their opening parentheses from
 491  * left to right.  In the expression {@code ((A)(B(C)))}, for example, there
 492  * are four such groups: </p>
 493  *
 494  * <ol style="margin-left:2em;">
 495  *   <li> {@code ((A)(B(C)))}
 496  *   <li> {@code (A)}
 497  *   <li> {@code (B(C))}
 498  *   <li> {@code (C)}
 499  * </ol>
 500  *
 501  * <p> Group zero always stands for the entire expression.
 502  *
 503  * <p> Capturing groups are so named because, during a match, each subsequence
 504  * of the input sequence that matches such a group is saved.  The captured
 505  * subsequence may be used later in the expression, via a back reference, and
 506  * may also be retrieved from the matcher once the match operation is complete.
 507  *
 508  * <h4><a id="groupname">Group name</a></h4>
 509  * <p>A capturing group can also be assigned a "name", a {@code named-capturing group},
 510  * and then be back-referenced later by the "name". Group names are composed of
 511  * the following characters. The first character must be a {@code letter}.
 512  *
 513  * <ul>
 514  *   <li> The uppercase letters {@code 'A'} through {@code 'Z'}
 515  *        (<code>'\u0041'</code>&nbsp;through&nbsp;<code>'\u005a'</code>),
 516  *   <li> The lowercase letters {@code 'a'} through {@code 'z'}
 517  *        (<code>'\u0061'</code>&nbsp;through&nbsp;<code>'\u007a'</code>),
 518  *   <li> The digits {@code '0'} through {@code '9'}
 519  *        (<code>'\u0030'</code>&nbsp;through&nbsp;<code>'\u0039'</code>),
 520  * </ul>
 521  *
 522  * <p> A {@code named-capturing group} is still numbered as described in
 523  * <a href="#gnumber">Group number</a>.
 524  *
 525  * <p> The captured input associated with a group is always the subsequence
 526  * that the group most recently matched.  If a group is evaluated a second time
 527  * because of quantification then its previously-captured value, if any, will
 528  * be retained if the second evaluation fails.  Matching the string
 529  * {@code "aba"} against the expression {@code (a(b)?)+}, for example, leaves
 530  * group two set to {@code "b"}.  All captured input is discarded at the
 531  * beginning of each match.
 532  *
 533  * <p> Groups beginning with {@code (?} are either pure, <i>non-capturing</i> groups
 534  * that do not capture text and do not count towards the group total, or
 535  * <i>named-capturing</i> group.
 536  *
 537  * <h3> Unicode support </h3>
 538  *
 539  * <p> This class is in conformance with Level 1 of <a
 540  * href="http://www.unicode.org/reports/tr18/"><i>Unicode Technical
 541  * Standard #18: Unicode Regular Expression</i></a>, plus RL2.1
 542  * Canonical Equivalents.
 543  * <p>
 544  * <b>Unicode escape sequences</b> such as <code>\u2014</code> in Java source code
 545  * are processed as described in section 3.3 of
 546  * <cite>The Java&trade; Language Specification</cite>.
 547  * Such escape sequences are also implemented directly by the regular-expression
 548  * parser so that Unicode escapes can be used in expressions that are read from
 549  * files or from the keyboard.  Thus the strings <code>"\u2014"</code> and
 550  * {@code "\\u2014"}, while not equal, compile into the same pattern, which
 551  * matches the character with hexadecimal value {@code 0x2014}.
 552  * <p>
 553  * A Unicode character can also be represented by using its <b>Hex notation</b>
 554  * (hexadecimal code point value) directly as described in construct
 555  * <code>\x{...}</code>, for example a supplementary character U+2011F can be
 556  * specified as <code>\x{2011F}</code>, instead of two consecutive Unicode escape
 557  * sequences of the surrogate pair <code>\uD840</code><code>\uDD1F</code>.
 558  * <p>
 559  * <b>Unicode character names</b> are supported by the named character construct
 560  * <code>\N{</code>...<code>}</code>, for example, <code>\N{WHITE SMILING FACE}</code>
 561  * specifies character <code>\u263A</code>. The character names supported
 562  * by this class are the valid Unicode character names matched by
 563  * {@link java.lang.Character#codePointOf(String) Character.codePointOf(name)}.
 564  * <p>
 565  * <a href="http://www.unicode.org/reports/tr18/#Default_Grapheme_Clusters">
 566  * <b>Unicode extended grapheme clusters</b></a> are supported by the grapheme
 567  * cluster matcher {@code \X} and the corresponding boundary matcher {@code \b{g}}.
 568  * <p>
 569  * Unicode scripts, blocks, categories and binary properties are written with
 570  * the {@code \p} and {@code \P} constructs as in Perl.
 571  * <code>\p{</code><i>prop</i><code>}</code> matches if
 572  * the input has the property <i>prop</i>, while <code>\P{</code><i>prop</i><code>}</code>
 573  * does not match if the input has that property.
 574  * <p>
 575  * Scripts, blocks, categories and binary properties can be used both inside
 576  * and outside of a character class.
 577  *
 578  * <p>
 579  * <b><a id="usc">Scripts</a></b> are specified either with the prefix {@code Is}, as in
 580  * {@code IsHiragana}, or by using  the {@code script} keyword (or its short
 581  * form {@code sc}) as in {@code script=Hiragana} or {@code sc=Hiragana}.
 582  * <p>
 583  * The script names supported by {@code Pattern} are the valid script names
 584  * accepted and defined by
 585  * {@link java.lang.Character.UnicodeScript#forName(String) UnicodeScript.forName}.
 586  *
 587  * <p>
 588  * <b><a id="ubc">Blocks</a></b> are specified with the prefix {@code In}, as in
 589  * {@code InMongolian}, or by using the keyword {@code block} (or its short
 590  * form {@code blk}) as in {@code block=Mongolian} or {@code blk=Mongolian}.
 591  * <p>
 592  * The block names supported by {@code Pattern} are the valid block names
 593  * accepted and defined by
 594  * {@link java.lang.Character.UnicodeBlock#forName(String) UnicodeBlock.forName}.
 595  * <p>
 596  *
 597  * <b><a id="ucc">Categories</a></b> may be specified with the optional prefix {@code Is}:
 598  * Both {@code \p{L}} and {@code \p{IsL}} denote the category of Unicode
 599  * letters. Same as scripts and blocks, categories can also be specified
 600  * by using the keyword {@code general_category} (or its short form
 601  * {@code gc}) as in {@code general_category=Lu} or {@code gc=Lu}.
 602  * <p>
 603  * The supported categories are those of
 604  * <a href="http://www.unicode.org/unicode/standard/standard.html">
 605  * <i>The Unicode Standard</i></a> in the version specified by the
 606  * {@link java.lang.Character Character} class. The category names are those
 607  * defined in the Standard, both normative and informative.
 608  * <p>
 609  *
 610  * <b><a id="ubpc">Binary properties</a></b> are specified with the prefix {@code Is}, as in
 611  * {@code IsAlphabetic}. The supported binary properties by {@code Pattern}
 612  * are
 613  * <ul>
 614  *   <li> Alphabetic
 615  *   <li> Ideographic
 616  *   <li> Letter
 617  *   <li> Lowercase
 618  *   <li> Uppercase
 619  *   <li> Titlecase
 620  *   <li> Punctuation
 621  *   <Li> Control
 622  *   <li> White_Space
 623  *   <li> Digit
 624  *   <li> Hex_Digit
 625  *   <li> Join_Control
 626  *   <li> Noncharacter_Code_Point
 627  *   <li> Assigned
 628  * </ul>
 629  * <p>
 630  * The following <b>Predefined Character classes</b> and <b>POSIX character classes</b>
 631  * are in conformance with the recommendation of <i>Annex C: Compatibility Properties</i>
 632  * of <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Regular Expression
 633  * </i></a>, when {@link #UNICODE_CHARACTER_CLASS} flag is specified.
 634  *
 635  * <table class="striped">
 636  * <caption style="display:none">predefined and posix character classes in Unicode mode</caption>
 637  * <thead>
 638  * <tr>
 639  * <th scope="col" id="predef_classes">Classes</th>
 640  * <th scope="col" id="predef_matches">Matches</th>
 641  * </tr>
 642  * </thead>
 643  * <tbody>
 644  * <tr><th scope="row">{@code \p{Lower}}</th>
 645  *     <td>A lowercase character:{@code \p{IsLowercase}}</td></tr>
 646  * <tr><th scope="row">{@code \p{Upper}}</th>
 647  *     <td>An uppercase character:{@code \p{IsUppercase}}</td></tr>
 648  * <tr><th scope="row">{@code \p{ASCII}}</th>
 649  *     <td>All ASCII:{@code [\x00-\x7F]}</td></tr>
 650  * <tr><th scope="row">{@code \p{Alpha}}</th>
 651  *     <td>An alphabetic character:{@code \p{IsAlphabetic}}</td></tr>
 652  * <tr><th scope="row">{@code \p{Digit}}</th>
 653  *     <td>A decimal digit character:{@code \p{IsDigit}}</td></tr>
 654  * <tr><th scope="row">{@code \p{Alnum}}</th>
 655  *     <td>An alphanumeric character:{@code [\p{IsAlphabetic}\p{IsDigit}]}</td></tr>
 656  * <tr><th scope="row">{@code \p{Punct}}</th>
 657  *     <td>A punctuation character:{@code \p{IsPunctuation}}</td></tr>
 658  * <tr><th scope="row">{@code \p{Graph}}</th>
 659  *     <td>A visible character: {@code [^\p{IsWhite_Space}\p{gc=Cc}\p{gc=Cs}\p{gc=Cn}]}</td></tr>
 660  * <tr><th scope="row">{@code \p{Print}}</th>
 661  *     <td>A printable character: {@code [\p{Graph}\p{Blank}&&[^\p{Cntrl}]]}</td></tr>
 662  * <tr><th scope="row">{@code \p{Blank}}</th>
 663  *     <td>A space or a tab: {@code [\p{IsWhite_Space}&&[^\p{gc=Zl}\p{gc=Zp}\x0a\x0b\x0c\x0d\x85]]}</td></tr>
 664  * <tr><th scope="row">{@code \p{Cntrl}}</th>
 665  *     <td>A control character: {@code \p{gc=Cc}}</td></tr>
 666  * <tr><th scope="row">{@code \p{XDigit}}</th>
 667  *     <td>A hexadecimal digit: {@code [\p{gc=Nd}\p{IsHex_Digit}]}</td></tr>
 668  * <tr><th scope="row">{@code \p{Space}}</th>
 669  *     <td>A whitespace character:{@code \p{IsWhite_Space}}</td></tr>
 670  * <tr><th scope="row">{@code \d}</th>
 671  *     <td>A digit: {@code \p{IsDigit}}</td></tr>
 672  * <tr><th scope="row">{@code \D}</th>
 673  *     <td>A non-digit: {@code [^\d]}</td></tr>
 674  * <tr><th scope="row">{@code \s}</th>
 675  *     <td>A whitespace character: {@code \p{IsWhite_Space}}</td></tr>
 676  * <tr><th scope="row">{@code \S}</th>
 677  *     <td>A non-whitespace character: {@code [^\s]}</td></tr>
 678  * <tr><th scope="row">{@code \w}</th>
 679  *     <td>A word character: {@code [\p{Alpha}\p{gc=Mn}\p{gc=Me}\p{gc=Mc}\p{Digit}\p{gc=Pc}\p{IsJoin_Control}]}</td></tr>
 680  * <tr><th scope="row">{@code \W}</th>
 681  *     <td>A non-word character: {@code [^\w]}</td></tr>
 682  * </tbody>
 683  * </table>
 684  * <p>
 685  * <a id="jcc">
 686  * Categories that behave like the java.lang.Character
 687  * boolean is<i>methodname</i> methods (except for the deprecated ones) are
 688  * available through the same <code>\p{</code><i>prop</i><code>}</code> syntax where
 689  * the specified property has the name <code>java<i>methodname</i></code></a>.
 690  *
 691  * <h3> Comparison to Perl 5 </h3>
 692  *
 693  * <p>The {@code Pattern} engine performs traditional NFA-based matching
 694  * with ordered alternation as occurs in Perl 5.
 695  *
 696  * <p> Perl constructs not supported by this class: </p>
 697  *
 698  * <ul>
 699  *    <li><p> The backreference constructs, <code>\g{</code><i>n</i><code>}</code> for
 700  *    the <i>n</i><sup>th</sup><a href="#cg">capturing group</a> and
 701  *    <code>\g{</code><i>name</i><code>}</code> for
 702  *    <a href="#groupname">named-capturing group</a>.
 703  *    </p></li>
 704  *
 705  *    <li><p> The conditional constructs
 706  *    {@code (?(}<i>condition</i>{@code )}<i>X</i>{@code )} and
 707  *    {@code (?(}<i>condition</i>{@code )}<i>X</i>{@code |}<i>Y</i>{@code )},
 708  *    </p></li>
 709  *
 710  *    <li><p> The embedded code constructs <code>(?{</code><i>code</i><code>})</code>
 711  *    and <code>(??{</code><i>code</i><code>})</code>,</p></li>
 712  *
 713  *    <li><p> The embedded comment syntax {@code (?#comment)}, and </p></li>
 714  *
 715  *    <li><p> The preprocessing operations {@code \l} <code>\u</code>,
 716  *    {@code \L}, and {@code \U}.  </p></li>
 717  *
 718  * </ul>
 719  *
 720  * <p> Constructs supported by this class but not by Perl: </p>
 721  *
 722  * <ul>
 723  *
 724  *    <li><p> Character-class union and intersection as described
 725  *    <a href="#cc">above</a>.</p></li>
 726  *
 727  * </ul>
 728  *
 729  * <p> Notable differences from Perl: </p>
 730  *
 731  * <ul>
 732  *
 733  *    <li><p> In Perl, {@code \1} through {@code \9} are always interpreted
 734  *    as back references; a backslash-escaped number greater than {@code 9} is
 735  *    treated as a back reference if at least that many subexpressions exist,
 736  *    otherwise it is interpreted, if possible, as an octal escape.  In this
 737  *    class octal escapes must always begin with a zero. In this class,
 738  *    {@code \1} through {@code \9} are always interpreted as back
 739  *    references, and a larger number is accepted as a back reference if at
 740  *    least that many subexpressions exist at that point in the regular
 741  *    expression, otherwise the parser will drop digits until the number is
 742  *    smaller or equal to the existing number of groups or it is one digit.
 743  *    </p></li>
 744  *
 745  *    <li><p> Perl uses the {@code g} flag to request a match that resumes
 746  *    where the last match left off.  This functionality is provided implicitly
 747  *    by the {@link Matcher} class: Repeated invocations of the {@link
 748  *    Matcher#find find} method will resume where the last match left off,
 749  *    unless the matcher is reset.  </p></li>
 750  *
 751  *    <li><p> In Perl, embedded flags at the top level of an expression affect
 752  *    the whole expression.  In this class, embedded flags always take effect
 753  *    at the point at which they appear, whether they are at the top level or
 754  *    within a group; in the latter case, flags are restored at the end of the
 755  *    group just as in Perl.  </p></li>
 756  *
 757  * </ul>
 758  *
 759  *
 760  * <p> For a more precise description of the behavior of regular expression
 761  * constructs, please see <a href="http://www.oreilly.com/catalog/regex3/">
 762  * <i>Mastering Regular Expressions, 3nd Edition</i>, Jeffrey E. F. Friedl,
 763  * O'Reilly and Associates, 2006.</a>
 764  * </p>
 765  *
 766  * @see java.lang.String#split(String, int)
 767  * @see java.lang.String#split(String)
 768  *
 769  * @author      Mike McCloskey
 770  * @author      Mark Reinhold
 771  * @author      JSR-51 Expert Group
 772  * @since       1.4
 773  * @spec        JSR-51
 774  */
 775 
 776 public final class Pattern
 777     implements java.io.Serializable
 778 {
 779 
 780     /**
 781      * Regular expression modifier values.  Instead of being passed as
 782      * arguments, they can also be passed as inline modifiers.
 783      * For example, the following statements have the same effect.
 784      * <pre>
 785      * Pattern p1 = Pattern.compile("abc", Pattern.CASE_INSENSITIVE|Pattern.MULTILINE);
 786      * Pattern p2 = Pattern.compile("(?im)abc", 0);
 787      * </pre>
 788      */
 789 
 790     /**
 791      * Enables Unix lines mode.
 792      *
 793      * <p> In this mode, only the {@code '\n'} line terminator is recognized
 794      * in the behavior of {@code .}, {@code ^}, and {@code $}.
 795      *
 796      * <p> Unix lines mode can also be enabled via the embedded flag
 797      * expression&nbsp;{@code (?d)}.
 798      */
 799     public static final int UNIX_LINES = 0x01;
 800 
 801     /**
 802      * Enables case-insensitive matching.
 803      *
 804      * <p> By default, case-insensitive matching assumes that only characters
 805      * in the US-ASCII charset are being matched.  Unicode-aware
 806      * case-insensitive matching can be enabled by specifying the {@link
 807      * #UNICODE_CASE} flag in conjunction with this flag.
 808      *
 809      * <p> Case-insensitive matching can also be enabled via the embedded flag
 810      * expression&nbsp;{@code (?i)}.
 811      *
 812      * <p> Specifying this flag may impose a slight performance penalty.  </p>
 813      */
 814     public static final int CASE_INSENSITIVE = 0x02;
 815 
 816     /**
 817      * Permits whitespace and comments in pattern.
 818      *
 819      * <p> In this mode, whitespace is ignored, and embedded comments starting
 820      * with {@code #} are ignored until the end of a line.
 821      *
 822      * <p> Comments mode can also be enabled via the embedded flag
 823      * expression&nbsp;{@code (?x)}.
 824      */
 825     public static final int COMMENTS = 0x04;
 826 
 827     /**
 828      * Enables multiline mode.
 829      *
 830      * <p> In multiline mode the expressions {@code ^} and {@code $} match
 831      * just after or just before, respectively, a line terminator or the end of
 832      * the input sequence.  By default these expressions only match at the
 833      * beginning and the end of the entire input sequence.
 834      *
 835      * <p> Multiline mode can also be enabled via the embedded flag
 836      * expression&nbsp;{@code (?m)}.  </p>
 837      */
 838     public static final int MULTILINE = 0x08;
 839 
 840     /**
 841      * Enables literal parsing of the pattern.
 842      *
 843      * <p> When this flag is specified then the input string that specifies
 844      * the pattern is treated as a sequence of literal characters.
 845      * Metacharacters or escape sequences in the input sequence will be
 846      * given no special meaning.
 847      *
 848      * <p>The flags CASE_INSENSITIVE and UNICODE_CASE retain their impact on
 849      * matching when used in conjunction with this flag. The other flags
 850      * become superfluous.
 851      *
 852      * <p> There is no embedded flag character for enabling literal parsing.
 853      * @since 1.5
 854      */
 855     public static final int LITERAL = 0x10;
 856 
 857     /**
 858      * Enables dotall mode.
 859      *
 860      * <p> In dotall mode, the expression {@code .} matches any character,
 861      * including a line terminator.  By default this expression does not match
 862      * line terminators.
 863      *
 864      * <p> Dotall mode can also be enabled via the embedded flag
 865      * expression&nbsp;{@code (?s)}.  (The {@code s} is a mnemonic for
 866      * "single-line" mode, which is what this is called in Perl.)  </p>
 867      */
 868     public static final int DOTALL = 0x20;
 869 
 870     /**
 871      * Enables Unicode-aware case folding.
 872      *
 873      * <p> When this flag is specified then case-insensitive matching, when
 874      * enabled by the {@link #CASE_INSENSITIVE} flag, is done in a manner
 875      * consistent with the Unicode Standard.  By default, case-insensitive
 876      * matching assumes that only characters in the US-ASCII charset are being
 877      * matched.
 878      *
 879      * <p> Unicode-aware case folding can also be enabled via the embedded flag
 880      * expression&nbsp;{@code (?u)}.
 881      *
 882      * <p> Specifying this flag may impose a performance penalty.  </p>
 883      */
 884     public static final int UNICODE_CASE = 0x40;
 885 
 886     /**
 887      * Enables canonical equivalence.
 888      *
 889      * <p> When this flag is specified then two characters will be considered
 890      * to match if, and only if, their full canonical decompositions match.
 891      * The expression <code>"a\u030A"</code>, for example, will match the
 892      * string <code>"\u00E5"</code> when this flag is specified.  By default,
 893      * matching does not take canonical equivalence into account.
 894      *
 895      * <p> There is no embedded flag character for enabling canonical
 896      * equivalence.
 897      *
 898      * <p> Specifying this flag may impose a performance penalty.  </p>
 899      */
 900     public static final int CANON_EQ = 0x80;
 901 
 902     /**
 903      * Enables the Unicode version of <i>Predefined character classes</i> and
 904      * <i>POSIX character classes</i>.
 905      *
 906      * <p> When this flag is specified then the (US-ASCII only)
 907      * <i>Predefined character classes</i> and <i>POSIX character classes</i>
 908      * are in conformance with
 909      * <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Technical
 910      * Standard #18: Unicode Regular Expression</i></a>
 911      * <i>Annex C: Compatibility Properties</i>.
 912      * <p>
 913      * The UNICODE_CHARACTER_CLASS mode can also be enabled via the embedded
 914      * flag expression&nbsp;{@code (?U)}.
 915      * <p>
 916      * The flag implies UNICODE_CASE, that is, it enables Unicode-aware case
 917      * folding.
 918      * <p>
 919      * Specifying this flag may impose a performance penalty.  </p>
 920      * @since 1.7
 921      */
 922     public static final int UNICODE_CHARACTER_CLASS = 0x100;
 923 
 924     /**
 925      * Contains all possible flags for compile(regex, flags).
 926      */
 927     private static final int ALL_FLAGS = CASE_INSENSITIVE | MULTILINE |
 928             DOTALL | UNICODE_CASE | CANON_EQ | UNIX_LINES | LITERAL |
 929             UNICODE_CHARACTER_CLASS | COMMENTS;
 930 
 931     /* Pattern has only two serialized components: The pattern string
 932      * and the flags, which are all that is needed to recompile the pattern
 933      * when it is deserialized.
 934      */
 935 
 936     /** use serialVersionUID from Merlin b59 for interoperability */
 937     private static final long serialVersionUID = 5073258162644648461L;
 938 
 939     /**
 940      * The original regular-expression pattern string.
 941      *
 942      * @serial
 943      */
 944     private String pattern;
 945 
 946     /**
 947      * The original pattern flags.
 948      *
 949      * @serial
 950      */
 951     private int flags;
 952 
 953     /**
 954      * The temporary pattern flags used during compiling. The flags might be turn
 955      * on and off by embedded flag.
 956      */
 957     private transient int flags0;
 958 
 959     /**
 960      * Boolean indicating this Pattern is compiled; this is necessary in order
 961      * to lazily compile deserialized Patterns.
 962      */
 963     private transient volatile boolean compiled;
 964 
 965     /**
 966      * The normalized pattern string.
 967      */
 968     private transient String normalizedPattern;
 969 
 970     /**
 971      * The starting point of state machine for the find operation.  This allows
 972      * a match to start anywhere in the input.
 973      */
 974     transient Node root;
 975 
 976     /**
 977      * The root of object tree for a match operation.  The pattern is matched
 978      * at the beginning.  This may include a find that uses BnM or a First
 979      * node.
 980      */
 981     transient Node matchRoot;
 982 
 983     /**
 984      * Temporary storage used by parsing pattern slice.
 985      */
 986     transient int[] buffer;
 987 
 988     /**
 989      * A temporary storage used for predicate for double return.
 990      */
 991     transient CharPredicate predicate;
 992 
 993     /**
 994      * Map the "name" of the "named capturing group" to its group id
 995      * node.
 996      */
 997     transient volatile Map<String, Integer> namedGroups;
 998 
 999     /**
1000      * Temporary storage used while parsing group references.
1001      */
1002     transient GroupHead[] groupNodes;
1003 
1004     /**
1005      * Temporary storage used to store the top level closure nodes.
1006      */
1007     transient List<Node> topClosureNodes;
1008 
1009     /**
1010      * The number of top greedy closure nodes in this Pattern. Used by
1011      * matchers to allocate storage needed for a IntHashSet to keep the
1012      * beginning pos {@code i} of all failed match.
1013      */
1014     transient int localTCNCount;
1015 
1016     /*
1017      * Turn off the stop-exponential-backtracking optimization if there
1018      * is a group ref in the pattern.
1019      */
1020     transient boolean hasGroupRef;
1021 
1022     /**
1023      * Temporary null terminated code point array used by pattern compiling.
1024      */
1025     private transient int[] temp;
1026 
1027     /**
1028      * The number of capturing groups in this Pattern. Used by matchers to
1029      * allocate storage needed to perform a match.
1030      */
1031     transient int capturingGroupCount;
1032 
1033     /**
1034      * The local variable count used by parsing tree. Used by matchers to
1035      * allocate storage needed to perform a match.
1036      */
1037     transient int localCount;
1038 
1039     /**
1040      * Index into the pattern string that keeps track of how much has been
1041      * parsed.
1042      */
1043     private transient int cursor;
1044 
1045     /**
1046      * Holds the length of the pattern string.
1047      */
1048     private transient int patternLength;
1049 
1050     /**
1051      * If the Start node might possibly match supplementary characters.
1052      * It is set to true during compiling if
1053      * (1) There is supplementary char in pattern, or
1054      * (2) There is complement node of a "family" CharProperty
1055      */
1056     private transient boolean hasSupplementary;
1057 
1058     /**
1059      * Compiles the given regular expression into a pattern.
1060      *
1061      * @param  regex
1062      *         The expression to be compiled
1063      * @return the given regular expression compiled into a pattern
1064      * @throws  PatternSyntaxException
1065      *          If the expression's syntax is invalid
1066      */
1067     public static Pattern compile(String regex) {
1068         return new Pattern(regex, 0);
1069     }
1070 
1071     /**
1072      * Compiles the given regular expression into a pattern with the given
1073      * flags.
1074      *
1075      * @param  regex
1076      *         The expression to be compiled
1077      *
1078      * @param  flags
1079      *         Match flags, a bit mask that may include
1080      *         {@link #CASE_INSENSITIVE}, {@link #MULTILINE}, {@link #DOTALL},
1081      *         {@link #UNICODE_CASE}, {@link #CANON_EQ}, {@link #UNIX_LINES},
1082      *         {@link #LITERAL}, {@link #UNICODE_CHARACTER_CLASS}
1083      *         and {@link #COMMENTS}
1084      *
1085      * @return the given regular expression compiled into a pattern with the given flags
1086      * @throws  IllegalArgumentException
1087      *          If bit values other than those corresponding to the defined
1088      *          match flags are set in {@code flags}
1089      *
1090      * @throws  PatternSyntaxException
1091      *          If the expression's syntax is invalid
1092      */
1093     public static Pattern compile(String regex, int flags) {
1094         return new Pattern(regex, flags);
1095     }
1096 
1097     /**
1098      * Returns the regular expression from which this pattern was compiled.
1099      *
1100      * @return  The source of this pattern
1101      */
1102     public String pattern() {
1103         return pattern;
1104     }
1105 
1106     /**
1107      * <p>Returns the string representation of this pattern. This
1108      * is the regular expression from which this pattern was
1109      * compiled.</p>
1110      *
1111      * @return  The string representation of this pattern
1112      * @since 1.5
1113      */
1114     public String toString() {
1115         return pattern;
1116     }
1117 
1118     /**
1119      * Creates a matcher that will match the given input against this pattern.
1120      *
1121      * @param  input
1122      *         The character sequence to be matched
1123      *
1124      * @return  A new matcher for this pattern
1125      */
1126     public Matcher matcher(CharSequence input) {
1127         if (!compiled) {
1128             synchronized(this) {
1129                 if (!compiled)
1130                     compile();
1131             }
1132         }
1133         Matcher m = new Matcher(this, input);
1134         return m;
1135     }
1136 
1137     /**
1138      * Returns this pattern's match flags.
1139      *
1140      * @return  The match flags specified when this pattern was compiled
1141      */
1142     public int flags() {
1143         return flags0;
1144     }
1145 
1146     /**
1147      * Compiles the given regular expression and attempts to match the given
1148      * input against it.
1149      *
1150      * <p> An invocation of this convenience method of the form
1151      *
1152      * <blockquote><pre>
1153      * Pattern.matches(regex, input);</pre></blockquote>
1154      *
1155      * behaves in exactly the same way as the expression
1156      *
1157      * <blockquote><pre>
1158      * Pattern.compile(regex).matcher(input).matches()</pre></blockquote>
1159      *
1160      * <p> If a pattern is to be used multiple times, compiling it once and reusing
1161      * it will be more efficient than invoking this method each time.  </p>
1162      *
1163      * @param  regex
1164      *         The expression to be compiled
1165      *
1166      * @param  input
1167      *         The character sequence to be matched
1168      * @return whether or not the regular expression matches on the input
1169      * @throws  PatternSyntaxException
1170      *          If the expression's syntax is invalid
1171      */
1172     public static boolean matches(String regex, CharSequence input) {
1173         Pattern p = Pattern.compile(regex);
1174         Matcher m = p.matcher(input);
1175         return m.matches();
1176     }
1177 
1178     /**
1179      * Splits the given input sequence around matches of this pattern.
1180      *
1181      * <p> The array returned by this method contains each substring of the
1182      * input sequence that is terminated by another subsequence that matches
1183      * this pattern or is terminated by the end of the input sequence.  The
1184      * substrings in the array are in the order in which they occur in the
1185      * input. If this pattern does not match any subsequence of the input then
1186      * the resulting array has just one element, namely the input sequence in
1187      * string form.
1188      *
1189      * <p> When there is a positive-width match at the beginning of the input
1190      * sequence then an empty leading substring is included at the beginning
1191      * of the resulting array. A zero-width match at the beginning however
1192      * never produces such empty leading substring.
1193      *
1194      * <p> The {@code limit} parameter controls the number of times the
1195      * pattern is applied and therefore affects the length of the resulting
1196      * array.
1197      * <ul>
1198      *    <li><p>
1199      *    If the <i>limit</i> is positive then the pattern will be applied
1200      *    at most <i>limit</i>&nbsp;-&nbsp;1 times, the array's length will be
1201      *    no greater than <i>limit</i>, and the array's last entry will contain
1202      *    all input beyond the last matched delimiter.</p></li>
1203      *
1204      *    <li><p>
1205      *    If the <i>limit</i> is zero then the pattern will be applied as
1206      *    many times as possible, the array can have any length, and trailing
1207      *    empty strings will be discarded.</p></li>
1208      *
1209      *    <li><p>
1210      *    If the <i>limit</i> is negative then the pattern will be applied
1211      *    as many times as possible and the array can have any length.</p></li>
1212      * </ul>
1213      *
1214      * <p> The input {@code "boo:and:foo"}, for example, yields the following
1215      * results with these parameters:
1216      *
1217      * <table class="plain" style="margin-left:2em;">
1218      * <caption style="display:none">Split example showing regex, limit, and result</caption>
1219      * <thead>
1220      * <tr>
1221      *     <th scope="col">Regex</th>
1222      *     <th scope="col">Limit</th>
1223      *     <th scope="col">Result</th>
1224      * </tr>
1225      * </thead>
1226      * <tbody>
1227      * <tr><th scope="row" rowspan="3" style="font-weight:normal">:</th>
1228      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">2</th>
1229      *     <td>{@code { "boo", "and:foo" }}</td></tr>
1230      * <tr><!-- : -->
1231      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
1232      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
1233      * <tr><!-- : -->
1234      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
1235      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
1236      * <tr><th scope="row" rowspan="3" style="font-weight:normal">o</th>
1237      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
1238      *     <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
1239      * <tr><!-- o -->
1240      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
1241      *     <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
1242      * <tr><!-- o -->
1243      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">0</th>
1244      *     <td>{@code { "b", "", ":and:f" }}</td></tr>
1245      * </tbody>
1246      * </table>
1247      *
1248      * @param  input
1249      *         The character sequence to be split
1250      *
1251      * @param  limit
1252      *         The result threshold, as described above
1253      *
1254      * @return  The array of strings computed by splitting the input
1255      *          around matches of this pattern
1256      */
1257     public String[] split(CharSequence input, int limit) {
1258         int index = 0;
1259         boolean matchLimited = limit > 0;
1260         ArrayList<String> matchList = new ArrayList<>();
1261         Matcher m = matcher(input);
1262 
1263         // Add segments before each match found
1264         while(m.find()) {
1265             if (!matchLimited || matchList.size() < limit - 1) {
1266                 if (index == 0 && index == m.start() && m.start() == m.end()) {
1267                     // no empty leading substring included for zero-width match
1268                     // at the beginning of the input char sequence.
1269                     continue;
1270                 }
1271                 String match = input.subSequence(index, m.start()).toString();
1272                 matchList.add(match);
1273                 index = m.end();
1274             } else if (matchList.size() == limit - 1) { // last one
1275                 String match = input.subSequence(index,
1276                                                  input.length()).toString();
1277                 matchList.add(match);
1278                 index = m.end();
1279             }
1280         }
1281 
1282         // If no match was found, return this
1283         if (index == 0)
1284             return new String[] {input.toString()};
1285 
1286         // Add remaining segment
1287         if (!matchLimited || matchList.size() < limit)
1288             matchList.add(input.subSequence(index, input.length()).toString());
1289 
1290         // Construct result
1291         int resultSize = matchList.size();
1292         if (limit == 0)
1293             while (resultSize > 0 && matchList.get(resultSize-1).isEmpty())
1294                 resultSize--;
1295         String[] result = new String[resultSize];
1296         return matchList.subList(0, resultSize).toArray(result);
1297     }
1298 
1299     /**
1300      * Splits the given input sequence around matches of this pattern.
1301      *
1302      * <p> This method works as if by invoking the two-argument {@link
1303      * #split(java.lang.CharSequence, int) split} method with the given input
1304      * sequence and a limit argument of zero.  Trailing empty strings are
1305      * therefore not included in the resulting array. </p>
1306      *
1307      * <p> The input {@code "boo:and:foo"}, for example, yields the following
1308      * results with these expressions:
1309      *
1310      * <table class="plain" style="margin-left:2em">
1311      * <caption style="display:none">Split examples showing regex and result</caption>
1312      * <thead>
1313      * <tr>
1314      *  <th scope="col">Regex</th>
1315      *  <th scope="col">Result</th>
1316      * </tr>
1317      * </thead>
1318      * <tbody>
1319      * <tr><th scope="row" style="text-weight:normal">:</th>
1320      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
1321      * <tr><th scope="row" style="text-weight:normal">o</th>
1322      *     <td>{@code { "b", "", ":and:f" }}</td></tr>
1323      * </tbody>
1324      * </table>
1325      *
1326      *
1327      * @param  input
1328      *         The character sequence to be split
1329      *
1330      * @return  The array of strings computed by splitting the input
1331      *          around matches of this pattern
1332      */
1333     public String[] split(CharSequence input) {
1334         return split(input, 0);
1335     }
1336 
1337     /**
1338      * Returns a literal pattern {@code String} for the specified
1339      * {@code String}.
1340      *
1341      * <p>This method produces a {@code String} that can be used to
1342      * create a {@code Pattern} that would match the string
1343      * {@code s} as if it were a literal pattern.</p> Metacharacters
1344      * or escape sequences in the input sequence will be given no special
1345      * meaning.
1346      *
1347      * @param  s The string to be literalized
1348      * @return  A literal string replacement
1349      * @since 1.5
1350      */
1351     public static String quote(String s) {
1352         int slashEIndex = s.indexOf("\\E");
1353         if (slashEIndex == -1)
1354             return "\\Q" + s + "\\E";
1355 
1356         int lenHint = s.length();
1357         lenHint = (lenHint < Integer.MAX_VALUE - 8 - lenHint) ?
1358                 (lenHint << 1) : (Integer.MAX_VALUE - 8);
1359 
1360         StringBuilder sb = new StringBuilder(lenHint);
1361         sb.append("\\Q");
1362         int current = 0;
1363         do {
1364             sb.append(s, current, slashEIndex)
1365                     .append("\\E\\\\E\\Q");
1366             current = slashEIndex + 2;
1367         } while ((slashEIndex = s.indexOf("\\E", current)) != -1);
1368 
1369         return sb.append(s, current, s.length())
1370                 .append("\\E")
1371                 .toString();
1372     }
1373 
1374     /**
1375      * Recompile the Pattern instance from a stream.  The original pattern
1376      * string is read in and the object tree is recompiled from it.
1377      */
1378     private void readObject(java.io.ObjectInputStream s)
1379         throws java.io.IOException, ClassNotFoundException {
1380 
1381         // Read in all fields
1382         s.defaultReadObject();
1383 
1384         // reset the flags
1385         flags0 = flags;
1386 
1387         // Initialize counts
1388         capturingGroupCount = 1;
1389         localCount = 0;
1390         localTCNCount = 0;
1391 
1392         // if length > 0, the Pattern is lazily compiled
1393         if (pattern.isEmpty()) {
1394             root = new Start(lastAccept);
1395             matchRoot = lastAccept;
1396             compiled = true;
1397         }
1398     }
1399 
1400     /**
1401      * This private constructor is used to create all Patterns. The pattern
1402      * string and match flags are all that is needed to completely describe
1403      * a Pattern. An empty pattern string results in an object tree with
1404      * only a Start node and a LastNode node.
1405      */
1406     private Pattern(String p, int f) {
1407         if ((f & ~ALL_FLAGS) != 0) {
1408             throw new IllegalArgumentException("Unknown flag 0x"
1409                                                + Integer.toHexString(f));
1410         }
1411         pattern = p;
1412         flags = f;
1413 
1414         // to use UNICODE_CASE if UNICODE_CHARACTER_CLASS present
1415         if ((flags & UNICODE_CHARACTER_CLASS) != 0)
1416             flags |= UNICODE_CASE;
1417 
1418         // 'flags' for compiling
1419         flags0 = flags;
1420 
1421         // Reset group index count
1422         capturingGroupCount = 1;
1423         localCount = 0;
1424         localTCNCount = 0;
1425 
1426         if (!pattern.isEmpty()) {
1427             compile();
1428         } else {
1429             root = new Start(lastAccept);
1430             matchRoot = lastAccept;
1431         }
1432     }
1433 
1434     /**
1435      * The pattern is converted to normalized form ({@link
1436      * java.text.Normalizer.Form#NFC NFC}, canonical decomposition,
1437      * followed by canonical composition for the character class
1438      * part, and {@link java.text.Normalizer.Form#NFD NFD},
1439      * canonical decomposition for the rest), and then a pure
1440      * group is constructed to match canonical equivalences of the
1441      * characters.
1442      */
1443     private static String normalize(String pattern) {
1444         int plen = pattern.length();
1445         StringBuilder pbuf = new StringBuilder(plen);
1446         char last = 0;
1447         int lastStart = 0;
1448         char cc = 0;
1449         for (int i = 0; i < plen;) {
1450             char c = pattern.charAt(i);
1451             if (cc == 0 &&    // top level
1452                 c == '\\' && i + 1 < plen && pattern.charAt(i + 1) == '\\') {
1453                 i += 2; last = 0;
1454                 continue;
1455             }
1456             if (c == '[' && last != '\\') {
1457                 if (cc == 0) {
1458                     if (lastStart < i)
1459                         normalizeSlice(pattern, lastStart, i, pbuf);
1460                     lastStart = i;
1461                 }
1462                 cc++;
1463             } else if (c == ']' && last != '\\') {
1464                 cc--;
1465                 if (cc == 0) {
1466                     normalizeClazz(pattern, lastStart, i + 1, pbuf);
1467                     lastStart = i + 1;
1468                 }
1469             }
1470             last = c;
1471             i++;
1472         }
1473         assert (cc == 0);
1474         if (lastStart < plen)
1475             normalizeSlice(pattern, lastStart, plen, pbuf);
1476         return pbuf.toString();
1477     }
1478 
1479     private static void normalizeSlice(String src, int off, int limit,
1480                                        StringBuilder dst)
1481     {
1482         int len = src.length();
1483         int off0 = off;
1484         while (off < limit && ASCII.isAscii(src.charAt(off))) {
1485             off++;
1486         }
1487         if (off == limit) {
1488             dst.append(src, off0, limit);
1489             return;
1490         }
1491         off--;
1492         if (off < off0)
1493             off = off0;
1494         else
1495             dst.append(src, off0, off);
1496         while (off < limit) {
1497             int ch0 = src.codePointAt(off);
1498             if (".$|()[]{}^?*+\\".indexOf(ch0) != -1) {
1499                 dst.append((char)ch0);
1500                 off++;
1501                 continue;
1502             }
1503             int j = off + Character.charCount(ch0);
1504             int ch1;
1505             while (j < limit) {
1506                 ch1 = src.codePointAt(j);
1507                 if (Grapheme.isBoundary(ch0, ch1))
1508                     break;
1509                 ch0 = ch1;
1510                 j += Character.charCount(ch1);
1511             }
1512             String seq = src.substring(off, j);
1513             String nfd = Normalizer.normalize(seq, Normalizer.Form.NFD);
1514             off = j;
1515             if (nfd.length() > 1) {
1516                 ch0 = nfd.codePointAt(0);
1517                 ch1 = nfd.codePointAt(Character.charCount(ch0));
1518                 if (Character.getType(ch1) == Character.NON_SPACING_MARK) {
1519                     Set<String> altns = new LinkedHashSet<>();
1520                     altns.add(seq);
1521                     produceEquivalentAlternation(nfd, altns);
1522                     dst.append("(?:");
1523                     altns.forEach( s -> dst.append(s).append('|'));
1524                     dst.delete(dst.length() - 1, dst.length());
1525                     dst.append(")");
1526                     continue;
1527                 }
1528             }
1529             String nfc = Normalizer.normalize(seq, Normalizer.Form.NFC);
1530             if (!seq.equals(nfc) && !nfd.equals(nfc))
1531                 dst.append("(?:" + seq + "|" + nfd  + "|" + nfc + ")");
1532             else if (!seq.equals(nfd))
1533                 dst.append("(?:" + seq + "|" + nfd + ")");
1534             else
1535                 dst.append(seq);
1536         }
1537     }
1538 
1539     private static void normalizeClazz(String src, int off, int limit,
1540                                        StringBuilder dst)
1541     {
1542         dst.append(Normalizer.normalize(src.substring(off, limit), Form.NFC));
1543     }
1544 
1545     /**
1546      * Given a specific sequence composed of a regular character and
1547      * combining marks that follow it, produce the alternation that will
1548      * match all canonical equivalences of that sequence.
1549      */
1550     private static void produceEquivalentAlternation(String src,
1551                                                      Set<String> dst)
1552     {
1553         int len = countChars(src, 0, 1);
1554         if (src.length() == len) {
1555             dst.add(src);  // source has one character.
1556             return;
1557         }
1558         String base = src.substring(0,len);
1559         String combiningMarks = src.substring(len);
1560         String[] perms = producePermutations(combiningMarks);
1561         // Add combined permutations
1562         for(int x = 0; x < perms.length; x++) {
1563             String next = base + perms[x];
1564             dst.add(next);
1565             next = composeOneStep(next);
1566             if (next != null) {
1567                 produceEquivalentAlternation(next, dst);
1568             }
1569         }
1570     }
1571 
1572     /**
1573      * Returns an array of strings that have all the possible
1574      * permutations of the characters in the input string.
1575      * This is used to get a list of all possible orderings
1576      * of a set of combining marks. Note that some of the permutations
1577      * are invalid because of combining class collisions, and these
1578      * possibilities must be removed because they are not canonically
1579      * equivalent.
1580      */
1581     private static String[] producePermutations(String input) {
1582         if (input.length() == countChars(input, 0, 1))
1583             return new String[] {input};
1584 
1585         if (input.length() == countChars(input, 0, 2)) {
1586             int c0 = Character.codePointAt(input, 0);
1587             int c1 = Character.codePointAt(input, Character.charCount(c0));
1588             if (getClass(c1) == getClass(c0)) {
1589                 return new String[] {input};
1590             }
1591             String[] result = new String[2];
1592             result[0] = input;
1593             StringBuilder sb = new StringBuilder(2);
1594             sb.appendCodePoint(c1);
1595             sb.appendCodePoint(c0);
1596             result[1] = sb.toString();
1597             return result;
1598         }
1599 
1600         int length = 1;
1601         int nCodePoints = countCodePoints(input);
1602         for(int x=1; x<nCodePoints; x++)
1603             length = length * (x+1);
1604 
1605         String[] temp = new String[length];
1606 
1607         int combClass[] = new int[nCodePoints];
1608         for(int x=0, i=0; x<nCodePoints; x++) {
1609             int c = Character.codePointAt(input, i);
1610             combClass[x] = getClass(c);
1611             i +=  Character.charCount(c);
1612         }
1613 
1614         // For each char, take it out and add the permutations
1615         // of the remaining chars
1616         int index = 0;
1617         int len;
1618         // offset maintains the index in code units.
1619 loop:   for(int x=0, offset=0; x<nCodePoints; x++, offset+=len) {
1620             len = countChars(input, offset, 1);
1621             for(int y=x-1; y>=0; y--) {
1622                 if (combClass[y] == combClass[x]) {
1623                     continue loop;
1624                 }
1625             }
1626             StringBuilder sb = new StringBuilder(input);
1627             String otherChars = sb.delete(offset, offset+len).toString();
1628             String[] subResult = producePermutations(otherChars);
1629 
1630             String prefix = input.substring(offset, offset+len);
1631             for (String sre : subResult)
1632                 temp[index++] = prefix + sre;
1633         }
1634         String[] result = new String[index];
1635         System.arraycopy(temp, 0, result, 0, index);
1636         return result;
1637     }
1638 
1639     private static int getClass(int c) {
1640         return sun.text.Normalizer.getCombiningClass(c);
1641     }
1642 
1643     /**
1644      * Attempts to compose input by combining the first character
1645      * with the first combining mark following it. Returns a String
1646      * that is the composition of the leading character with its first
1647      * combining mark followed by the remaining combining marks. Returns
1648      * null if the first two characters cannot be further composed.
1649      */
1650     private static String composeOneStep(String input) {
1651         int len = countChars(input, 0, 2);
1652         String firstTwoCharacters = input.substring(0, len);
1653         String result = Normalizer.normalize(firstTwoCharacters, Normalizer.Form.NFC);
1654         if (result.equals(firstTwoCharacters))
1655             return null;
1656         else {
1657             String remainder = input.substring(len);
1658             return result + remainder;
1659         }
1660     }
1661 
1662     /**
1663      * Preprocess any \Q...\E sequences in `temp', meta-quoting them.
1664      * See the description of `quotemeta' in perlfunc(1).
1665      */
1666     private void RemoveQEQuoting() {
1667         final int pLen = patternLength;
1668         int i = 0;
1669         while (i < pLen-1) {
1670             if (temp[i] != '\\')
1671                 i += 1;
1672             else if (temp[i + 1] != 'Q')
1673                 i += 2;
1674             else
1675                 break;
1676         }
1677         if (i >= pLen - 1)    // No \Q sequence found
1678             return;
1679         int j = i;
1680         i += 2;
1681         int[] newtemp = new int[j + 3*(pLen-i) + 2];
1682         System.arraycopy(temp, 0, newtemp, 0, j);
1683 
1684         boolean inQuote = true;
1685         boolean beginQuote = true;
1686         while (i < pLen) {
1687             int c = temp[i++];
1688             if (!ASCII.isAscii(c) || ASCII.isAlpha(c)) {
1689                 newtemp[j++] = c;
1690             } else if (ASCII.isDigit(c)) {
1691                 if (beginQuote) {
1692                     /*
1693                      * A unicode escape \[0xu] could be before this quote,
1694                      * and we don't want this numeric char to processed as
1695                      * part of the escape.
1696                      */
1697                     newtemp[j++] = '\\';
1698                     newtemp[j++] = 'x';
1699                     newtemp[j++] = '3';
1700                 }
1701                 newtemp[j++] = c;
1702             } else if (c != '\\') {
1703                 if (inQuote) newtemp[j++] = '\\';
1704                 newtemp[j++] = c;
1705             } else if (inQuote) {
1706                 if (temp[i] == 'E') {
1707                     i++;
1708                     inQuote = false;
1709                 } else {
1710                     newtemp[j++] = '\\';
1711                     newtemp[j++] = '\\';
1712                 }
1713             } else {
1714                 if (temp[i] == 'Q') {
1715                     i++;
1716                     inQuote = true;
1717                     beginQuote = true;
1718                     continue;
1719                 } else {
1720                     newtemp[j++] = c;
1721                     if (i != pLen)
1722                         newtemp[j++] = temp[i++];
1723                 }
1724             }
1725 
1726             beginQuote = false;
1727         }
1728 
1729         patternLength = j;
1730         temp = Arrays.copyOf(newtemp, j + 2); // double zero termination
1731     }
1732 
1733     /**
1734      * Copies regular expression to an int array and invokes the parsing
1735      * of the expression which will create the object tree.
1736      */
1737     private void compile() {
1738         // Handle canonical equivalences
1739         if (has(CANON_EQ) && !has(LITERAL)) {
1740             normalizedPattern = normalize(pattern);
1741         } else {
1742             normalizedPattern = pattern;
1743         }
1744         patternLength = normalizedPattern.length();
1745 
1746         // Copy pattern to int array for convenience
1747         // Use double zero to terminate pattern
1748         temp = new int[patternLength + 2];
1749 
1750         hasSupplementary = false;
1751         int c, count = 0;
1752         // Convert all chars into code points
1753         for (int x = 0; x < patternLength; x += Character.charCount(c)) {
1754             c = normalizedPattern.codePointAt(x);
1755             if (isSupplementary(c)) {
1756                 hasSupplementary = true;
1757             }
1758             temp[count++] = c;
1759         }
1760 
1761         patternLength = count;   // patternLength now in code points
1762 
1763         if (! has(LITERAL))
1764             RemoveQEQuoting();
1765 
1766         // Allocate all temporary objects here.
1767         buffer = new int[32];
1768         groupNodes = new GroupHead[10];
1769         namedGroups = null;
1770         topClosureNodes = new ArrayList<>(10);
1771 
1772         if (has(LITERAL)) {
1773             // Literal pattern handling
1774             matchRoot = newSlice(temp, patternLength, hasSupplementary);
1775             matchRoot.next = lastAccept;
1776         } else {
1777             // Start recursive descent parsing
1778             matchRoot = expr(lastAccept);
1779             // Check extra pattern characters
1780             if (patternLength != cursor) {
1781                 if (peek() == ')') {
1782                     throw error("Unmatched closing ')'");
1783                 } else {
1784                     throw error("Unexpected internal error");
1785                 }
1786             }
1787         }
1788 
1789         // Peephole optimization
1790         if (matchRoot instanceof Slice) {
1791             root = BnM.optimize(matchRoot);
1792             if (root == matchRoot) {
1793                 root = hasSupplementary ? new StartS(matchRoot) : new Start(matchRoot);
1794             }
1795         } else if (matchRoot instanceof Begin || matchRoot instanceof First) {
1796             root = matchRoot;
1797         } else {
1798             root = hasSupplementary ? new StartS(matchRoot) : new Start(matchRoot);
1799         }
1800 
1801         // Optimize the greedy Loop to prevent exponential backtracking, IF there
1802         // is no group ref in this pattern. With a non-negative localTCNCount value,
1803         // the greedy type Loop, Curly will skip the backtracking for any starting
1804         // position "i" that failed in the past.
1805         if (!hasGroupRef) {
1806             for (Node node : topClosureNodes) {
1807                 if (node instanceof Loop) {
1808                     // non-deterministic-greedy-group
1809                     ((Loop)node).posIndex = localTCNCount++;
1810                 }
1811             }
1812         }
1813 
1814         // Release temporary storage
1815         temp = null;
1816         buffer = null;
1817         groupNodes = null;
1818         patternLength = 0;
1819         compiled = true;
1820         topClosureNodes = null;
1821     }
1822 
1823     Map<String, Integer> namedGroups() {
1824         Map<String, Integer> groups = namedGroups;
1825         if (groups == null) {
1826             namedGroups = groups = new HashMap<>(2);
1827         }
1828         return groups;
1829     }
1830 
1831     /**
1832      * Used to accumulate information about a subtree of the object graph
1833      * so that optimizations can be applied to the subtree.
1834      */
1835     static final class TreeInfo {
1836         int minLength;
1837         int maxLength;
1838         boolean maxValid;
1839         boolean deterministic;
1840 
1841         TreeInfo() {
1842             reset();
1843         }
1844         void reset() {
1845             minLength = 0;
1846             maxLength = 0;
1847             maxValid = true;
1848             deterministic = true;
1849         }
1850     }
1851 
1852     /*
1853      * The following private methods are mainly used to improve the
1854      * readability of the code. In order to let the Java compiler easily
1855      * inline them, we should not put many assertions or error checks in them.
1856      */
1857 
1858     /**
1859      * Indicates whether a particular flag is set or not.
1860      */
1861     private boolean has(int f) {
1862         return (flags0 & f) != 0;
1863     }
1864 
1865     /**
1866      * Match next character, signal error if failed.
1867      */
1868     private void accept(int ch, String s) {
1869         int testChar = temp[cursor++];
1870         if (has(COMMENTS))
1871             testChar = parsePastWhitespace(testChar);
1872         if (ch != testChar) {
1873             throw error(s);
1874         }
1875     }
1876 
1877     /**
1878      * Mark the end of pattern with a specific character.
1879      */
1880     private void mark(int c) {
1881         temp[patternLength] = c;
1882     }
1883 
1884     /**
1885      * Peek the next character, and do not advance the cursor.
1886      */
1887     private int peek() {
1888         int ch = temp[cursor];
1889         if (has(COMMENTS))
1890             ch = peekPastWhitespace(ch);
1891         return ch;
1892     }
1893 
1894     /**
1895      * Read the next character, and advance the cursor by one.
1896      */
1897     private int read() {
1898         int ch = temp[cursor++];
1899         if (has(COMMENTS))
1900             ch = parsePastWhitespace(ch);
1901         return ch;
1902     }
1903 
1904     /**
1905      * Read the next character, and advance the cursor by one,
1906      * ignoring the COMMENTS setting
1907      */
1908     private int readEscaped() {
1909         int ch = temp[cursor++];
1910         return ch;
1911     }
1912 
1913     /**
1914      * Advance the cursor by one, and peek the next character.
1915      */
1916     private int next() {
1917         int ch = temp[++cursor];
1918         if (has(COMMENTS))
1919             ch = peekPastWhitespace(ch);
1920         return ch;
1921     }
1922 
1923     /**
1924      * Advance the cursor by one, and peek the next character,
1925      * ignoring the COMMENTS setting
1926      */
1927     private int nextEscaped() {
1928         int ch = temp[++cursor];
1929         return ch;
1930     }
1931 
1932     /**
1933      * If in xmode peek past whitespace and comments.
1934      */
1935     private int peekPastWhitespace(int ch) {
1936         while (ASCII.isSpace(ch) || ch == '#') {
1937             while (ASCII.isSpace(ch))
1938                 ch = temp[++cursor];
1939             if (ch == '#') {
1940                 ch = peekPastLine();
1941             }
1942         }
1943         return ch;
1944     }
1945 
1946     /**
1947      * If in xmode parse past whitespace and comments.
1948      */
1949     private int parsePastWhitespace(int ch) {
1950         while (ASCII.isSpace(ch) || ch == '#') {
1951             while (ASCII.isSpace(ch))
1952                 ch = temp[cursor++];
1953             if (ch == '#')
1954                 ch = parsePastLine();
1955         }
1956         return ch;
1957     }
1958 
1959     /**
1960      * xmode parse past comment to end of line.
1961      */
1962     private int parsePastLine() {
1963         int ch = temp[cursor++];
1964         while (ch != 0 && !isLineSeparator(ch))
1965             ch = temp[cursor++];
1966         return ch;
1967     }
1968 
1969     /**
1970      * xmode peek past comment to end of line.
1971      */
1972     private int peekPastLine() {
1973         int ch = temp[++cursor];
1974         while (ch != 0 && !isLineSeparator(ch))
1975             ch = temp[++cursor];
1976         return ch;
1977     }
1978 
1979     /**
1980      * Determines if character is a line separator in the current mode
1981      */
1982     private boolean isLineSeparator(int ch) {
1983         if (has(UNIX_LINES)) {
1984             return ch == '\n';
1985         } else {
1986             return (ch == '\n' ||
1987                     ch == '\r' ||
1988                     (ch|1) == '\u2029' ||
1989                     ch == '\u0085');
1990         }
1991     }
1992 
1993     /**
1994      * Read the character after the next one, and advance the cursor by two.
1995      */
1996     private int skip() {
1997         int i = cursor;
1998         int ch = temp[i+1];
1999         cursor = i + 2;
2000         return ch;
2001     }
2002 
2003     /**
2004      * Unread one next character, and retreat cursor by one.
2005      */
2006     private void unread() {
2007         cursor--;
2008     }
2009 
2010     /**
2011      * Internal method used for handling all syntax errors. The pattern is
2012      * displayed with a pointer to aid in locating the syntax error.
2013      */
2014     private PatternSyntaxException error(String s) {
2015         return new PatternSyntaxException(s, normalizedPattern,  cursor - 1);
2016     }
2017 
2018     /**
2019      * Determines if there is any supplementary character or unpaired
2020      * surrogate in the specified range.
2021      */
2022     private boolean findSupplementary(int start, int end) {
2023         for (int i = start; i < end; i++) {
2024             if (isSupplementary(temp[i]))
2025                 return true;
2026         }
2027         return false;
2028     }
2029 
2030     /**
2031      * Determines if the specified code point is a supplementary
2032      * character or unpaired surrogate.
2033      */
2034     private static final boolean isSupplementary(int ch) {
2035         return ch >= Character.MIN_SUPPLEMENTARY_CODE_POINT ||
2036                Character.isSurrogate((char)ch);
2037     }
2038 
2039     /**
2040      *  The following methods handle the main parsing. They are sorted
2041      *  according to their precedence order, the lowest one first.
2042      */
2043 
2044     /**
2045      * The expression is parsed with branch nodes added for alternations.
2046      * This may be called recursively to parse sub expressions that may
2047      * contain alternations.
2048      */
2049     private Node expr(Node end) {
2050         Node prev = null;
2051         Node firstTail = null;
2052         Branch branch = null;
2053         Node branchConn = null;
2054 
2055         for (;;) {
2056             Node node = sequence(end);
2057             Node nodeTail = root;      //double return
2058             if (prev == null) {
2059                 prev = node;
2060                 firstTail = nodeTail;
2061             } else {
2062                 // Branch
2063                 if (branchConn == null) {
2064                     branchConn = new BranchConn();
2065                     branchConn.next = end;
2066                 }
2067                 if (node == end) {
2068                     // if the node returned from sequence() is "end"
2069                     // we have an empty expr, set a null atom into
2070                     // the branch to indicate to go "next" directly.
2071                     node = null;
2072                 } else {
2073                     // the "tail.next" of each atom goes to branchConn
2074                     nodeTail.next = branchConn;
2075                 }
2076                 if (prev == branch) {
2077                     branch.add(node);
2078                 } else {
2079                     if (prev == end) {
2080                         prev = null;
2081                     } else {
2082                         // replace the "end" with "branchConn" at its tail.next
2083                         // when put the "prev" into the branch as the first atom.
2084                         firstTail.next = branchConn;
2085                     }
2086                     prev = branch = new Branch(prev, node, branchConn);
2087                 }
2088             }
2089             if (peek() != '|') {
2090                 return prev;
2091             }
2092             next();
2093         }
2094     }
2095 
2096     @SuppressWarnings("fallthrough")
2097     /**
2098      * Parsing of sequences between alternations.
2099      */
2100     private Node sequence(Node end) {
2101         Node head = null;
2102         Node tail = null;
2103         Node node = null;
2104     LOOP:
2105         for (;;) {
2106             int ch = peek();
2107             switch (ch) {
2108             case '(':
2109                 // Because group handles its own closure,
2110                 // we need to treat it differently
2111                 node = group0();
2112                 // Check for comment or flag group
2113                 if (node == null)
2114                     continue;
2115                 if (head == null)
2116                     head = node;
2117                 else
2118                     tail.next = node;
2119                 // Double return: Tail was returned in root
2120                 tail = root;
2121                 continue;
2122             case '[':
2123                 if (has(CANON_EQ) && !has(LITERAL))
2124                     node = new NFCCharProperty(clazz(true));
2125                 else
2126                     node = newCharProperty(clazz(true));
2127                 break;
2128             case '\\':
2129                 ch = nextEscaped();
2130                 if (ch == 'p' || ch == 'P') {
2131                     boolean oneLetter = true;
2132                     boolean comp = (ch == 'P');
2133                     ch = next(); // Consume { if present
2134                     if (ch != '{') {
2135                         unread();
2136                     } else {
2137                         oneLetter = false;
2138                     }
2139                     // node = newCharProperty(family(oneLetter, comp));
2140                     if (has(CANON_EQ) && !has(LITERAL))
2141                         node = new NFCCharProperty(family(oneLetter, comp));
2142                     else
2143                         node = newCharProperty(family(oneLetter, comp));
2144                 } else {
2145                     unread();
2146                     node = atom();
2147                 }
2148                 break;
2149             case '^':
2150                 next();
2151                 if (has(MULTILINE)) {
2152                     if (has(UNIX_LINES))
2153                         node = new UnixCaret();
2154                     else
2155                         node = new Caret();
2156                 } else {
2157                     node = new Begin();
2158                 }
2159                 break;
2160             case '$':
2161                 next();
2162                 if (has(UNIX_LINES))
2163                     node = new UnixDollar(has(MULTILINE));
2164                 else
2165                     node = new Dollar(has(MULTILINE));
2166                 break;
2167             case '.':
2168                 next();
2169                 if (has(DOTALL)) {
2170                     node = new CharProperty(ALL());
2171                 } else {
2172                     if (has(UNIX_LINES)) {
2173                         node = new CharProperty(UNIXDOT());
2174                     } else {
2175                         node = new CharProperty(DOT());
2176                     }
2177                 }
2178                 break;
2179             case '|':
2180             case ')':
2181                 break LOOP;
2182             case ']': // Now interpreting dangling ] and } as literals
2183             case '}':
2184                 node = atom();
2185                 break;
2186             case '?':
2187             case '*':
2188             case '+':
2189                 next();
2190                 throw error("Dangling meta character '" + ((char)ch) + "'");
2191             case 0:
2192                 if (cursor >= patternLength) {
2193                     break LOOP;
2194                 }
2195                 // Fall through
2196             default:
2197                 node = atom();
2198                 break;
2199             }
2200 
2201             node = closure(node);
2202             /* save the top dot-greedy nodes (.*, .+) as well
2203             if (node instanceof GreedyCharProperty &&
2204                 ((GreedyCharProperty)node).cp instanceof Dot) {
2205                 topClosureNodes.add(node);
2206             }
2207             */
2208             if (head == null) {
2209                 head = tail = node;
2210             } else {
2211                 tail.next = node;
2212                 tail = node;
2213             }
2214         }
2215         if (head == null) {
2216             return end;
2217         }
2218         tail.next = end;
2219         root = tail;      //double return
2220         return head;
2221     }
2222 
2223     @SuppressWarnings("fallthrough")
2224     /**
2225      * Parse and add a new Single or Slice.
2226      */
2227     private Node atom() {
2228         int first = 0;
2229         int prev = -1;
2230         boolean hasSupplementary = false;
2231         int ch = peek();
2232         for (;;) {
2233             switch (ch) {
2234             case '*':
2235             case '+':
2236             case '?':
2237             case '{':
2238                 if (first > 1) {
2239                     cursor = prev;    // Unwind one character
2240                     first--;
2241                 }
2242                 break;
2243             case '$':
2244             case '.':
2245             case '^':
2246             case '(':
2247             case '[':
2248             case '|':
2249             case ')':
2250                 break;
2251             case '\\':
2252                 ch = nextEscaped();
2253                 if (ch == 'p' || ch == 'P') { // Property
2254                     if (first > 0) { // Slice is waiting; handle it first
2255                         unread();
2256                         break;
2257                     } else { // No slice; just return the family node
2258                         boolean comp = (ch == 'P');
2259                         boolean oneLetter = true;
2260                         ch = next(); // Consume { if present
2261                         if (ch != '{')
2262                             unread();
2263                         else
2264                             oneLetter = false;
2265                         if (has(CANON_EQ) && !has(LITERAL))
2266                             return new NFCCharProperty(family(oneLetter, comp));
2267                         else
2268                             return newCharProperty(family(oneLetter, comp));
2269                     }
2270                 }
2271                 unread();
2272                 prev = cursor;
2273                 ch = escape(false, first == 0, false);
2274                 if (ch >= 0) {
2275                     append(ch, first);
2276                     first++;
2277                     if (isSupplementary(ch)) {
2278                         hasSupplementary = true;
2279                     }
2280                     ch = peek();
2281                     continue;
2282                 } else if (first == 0) {
2283                     return root;
2284                 }
2285                 // Unwind meta escape sequence
2286                 cursor = prev;
2287                 break;
2288             case 0:
2289                 if (cursor >= patternLength) {
2290                     break;
2291                 }
2292                 // Fall through
2293             default:
2294                 prev = cursor;
2295                 append(ch, first);
2296                 first++;
2297                 if (isSupplementary(ch)) {
2298                     hasSupplementary = true;
2299                 }
2300                 ch = next();
2301                 continue;
2302             }
2303             break;
2304         }
2305         if (first == 1) {
2306             return newCharProperty(single(buffer[0]));
2307         } else {
2308             return newSlice(buffer, first, hasSupplementary);
2309         }
2310     }
2311 
2312     private void append(int ch, int len) {
2313         if (len >= buffer.length) {
2314             int[] tmp = new int[len+len];
2315             System.arraycopy(buffer, 0, tmp, 0, len);
2316             buffer = tmp;
2317         }
2318         buffer[len] = ch;
2319     }
2320 
2321     /**
2322      * Parses a backref greedily, taking as many numbers as it
2323      * can. The first digit is always treated as a backref, but
2324      * multi digit numbers are only treated as a backref if at
2325      * least that many backrefs exist at this point in the regex.
2326      */
2327     private Node ref(int refNum) {
2328         boolean done = false;
2329         while(!done) {
2330             int ch = peek();
2331             switch(ch) {
2332             case '0':
2333             case '1':
2334             case '2':
2335             case '3':
2336             case '4':
2337             case '5':
2338             case '6':
2339             case '7':
2340             case '8':
2341             case '9':
2342                 int newRefNum = (refNum * 10) + (ch - '0');
2343                 // Add another number if it doesn't make a group
2344                 // that doesn't exist
2345                 if (capturingGroupCount - 1 < newRefNum) {
2346                     done = true;
2347                     break;
2348                 }
2349                 refNum = newRefNum;
2350                 read();
2351                 break;
2352             default:
2353                 done = true;
2354                 break;
2355             }
2356         }
2357         hasGroupRef = true;
2358         if (has(CASE_INSENSITIVE))
2359             return new CIBackRef(refNum, has(UNICODE_CASE));
2360         else
2361             return new BackRef(refNum);
2362     }
2363 
2364     /**
2365      * Parses an escape sequence to determine the actual value that needs
2366      * to be matched.
2367      * If -1 is returned and create was true a new object was added to the tree
2368      * to handle the escape sequence.
2369      * If the returned value is greater than zero, it is the value that
2370      * matches the escape sequence.
2371      */
2372     private int escape(boolean inclass, boolean create, boolean isrange) {
2373         int ch = skip();
2374         switch (ch) {
2375         case '0':
2376             return o();
2377         case '1':
2378         case '2':
2379         case '3':
2380         case '4':
2381         case '5':
2382         case '6':
2383         case '7':
2384         case '8':
2385         case '9':
2386             if (inclass) break;
2387             if (create) {
2388                 root = ref((ch - '0'));
2389             }
2390             return -1;
2391         case 'A':
2392             if (inclass) break;
2393             if (create) root = new Begin();
2394             return -1;
2395         case 'B':
2396             if (inclass) break;
2397             if (create) root = new Bound(Bound.NONE, has(UNICODE_CHARACTER_CLASS));
2398             return -1;
2399         case 'C':
2400             break;
2401         case 'D':
2402             if (create) {
2403                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2404                             CharPredicates.DIGIT() : CharPredicates.ASCII_DIGIT();
2405                 predicate = predicate.negate();
2406                 if (!inclass)
2407                     root = newCharProperty(predicate);
2408             }
2409             return -1;
2410         case 'E':
2411         case 'F':
2412             break;
2413         case 'G':
2414             if (inclass) break;
2415             if (create) root = new LastMatch();
2416             return -1;
2417         case 'H':
2418             if (create) {
2419                 predicate = HorizWS().negate();
2420                 if (!inclass)
2421                     root = newCharProperty(predicate);
2422             }
2423             return -1;
2424         case 'I':
2425         case 'J':
2426         case 'K':
2427         case 'L':
2428         case 'M':
2429             break;
2430         case 'N':
2431             return N();
2432         case 'O':
2433         case 'P':
2434         case 'Q':
2435             break;
2436         case 'R':
2437             if (inclass) break;
2438             if (create) root = new LineEnding();
2439             return -1;
2440         case 'S':
2441             if (create) {
2442                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2443                             CharPredicates.WHITE_SPACE() : CharPredicates.ASCII_SPACE();
2444                 predicate = predicate.negate();
2445                 if (!inclass)
2446                     root = newCharProperty(predicate);
2447             }
2448             return -1;
2449         case 'T':
2450         case 'U':
2451             break;
2452         case 'V':
2453             if (create) {
2454                 predicate = VertWS().negate();
2455                 if (!inclass)
2456                     root = newCharProperty(predicate);
2457             }
2458             return -1;
2459         case 'W':
2460             if (create) {
2461                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2462                             CharPredicates.WORD() : CharPredicates.ASCII_WORD();
2463                 predicate = predicate.negate();
2464                 if (!inclass)
2465                     root = newCharProperty(predicate);
2466             }
2467             return -1;
2468         case 'X':
2469             if (inclass) break;
2470             if (create) {
2471                 root = new XGrapheme();
2472             }
2473             return -1;
2474         case 'Y':
2475             break;
2476         case 'Z':
2477             if (inclass) break;
2478             if (create) {
2479                 if (has(UNIX_LINES))
2480                     root = new UnixDollar(false);
2481                 else
2482                     root = new Dollar(false);
2483             }
2484             return -1;
2485         case 'a':
2486             return '\007';
2487         case 'b':
2488             if (inclass) break;
2489             if (create) {
2490                 if (peek() == '{') {
2491                     if (skip() == 'g') {
2492                         if (read() == '}') {
2493                             root = new GraphemeBound();
2494                             return -1;
2495                         }
2496                         break;  // error missing trailing }
2497                     }
2498                     unread(); unread();
2499                 }
2500                 root = new Bound(Bound.BOTH, has(UNICODE_CHARACTER_CLASS));
2501             }
2502             return -1;
2503         case 'c':
2504             return c();
2505         case 'd':
2506             if (create) {
2507                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2508                             CharPredicates.DIGIT() : CharPredicates.ASCII_DIGIT();
2509                 if (!inclass)
2510                     root = newCharProperty(predicate);
2511             }
2512             return -1;
2513         case 'e':
2514             return '\033';
2515         case 'f':
2516             return '\f';
2517         case 'g':
2518             break;
2519         case 'h':
2520             if (create) {
2521                 predicate = HorizWS();
2522                 if (!inclass)
2523                     root = newCharProperty(predicate);
2524             }
2525             return -1;
2526         case 'i':
2527         case 'j':
2528             break;
2529         case 'k':
2530             if (inclass)
2531                 break;
2532             if (read() != '<')
2533                 throw error("\\k is not followed by '<' for named capturing group");
2534             String name = groupname(read());
2535             if (!namedGroups().containsKey(name))
2536                 throw error("named capturing group <" + name + "> does not exist");
2537             if (create) {
2538                 hasGroupRef = true;
2539                 if (has(CASE_INSENSITIVE))
2540                     root = new CIBackRef(namedGroups().get(name), has(UNICODE_CASE));
2541                 else
2542                     root = new BackRef(namedGroups().get(name));
2543             }
2544             return -1;
2545         case 'l':
2546         case 'm':
2547             break;
2548         case 'n':
2549             return '\n';
2550         case 'o':
2551         case 'p':
2552         case 'q':
2553             break;
2554         case 'r':
2555             return '\r';
2556         case 's':
2557             if (create) {
2558                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2559                             CharPredicates.WHITE_SPACE() : CharPredicates.ASCII_SPACE();
2560                 if (!inclass)
2561                     root = newCharProperty(predicate);
2562             }
2563             return -1;
2564         case 't':
2565             return '\t';
2566         case 'u':
2567             return u();
2568         case 'v':
2569             // '\v' was implemented as VT/0x0B in releases < 1.8 (though
2570             // undocumented). In JDK8 '\v' is specified as a predefined
2571             // character class for all vertical whitespace characters.
2572             // So [-1, root=VertWS node] pair is returned (instead of a
2573             // single 0x0B). This breaks the range if '\v' is used as
2574             // the start or end value, such as [\v-...] or [...-\v], in
2575             // which a single definite value (0x0B) is expected. For
2576             // compatibility concern '\013'/0x0B is returned if isrange.
2577             if (isrange)
2578                 return '\013';
2579             if (create) {
2580                 predicate = VertWS();
2581                 if (!inclass)
2582                     root = newCharProperty(predicate);
2583             }
2584             return -1;
2585         case 'w':
2586             if (create) {
2587                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2588                             CharPredicates.WORD() : CharPredicates.ASCII_WORD();
2589                 if (!inclass)
2590                     root = newCharProperty(predicate);
2591             }
2592             return -1;
2593         case 'x':
2594             return x();
2595         case 'y':
2596             break;
2597         case 'z':
2598             if (inclass) break;
2599             if (create) root = new End();
2600             return -1;
2601         default:
2602             return ch;
2603         }
2604         throw error("Illegal/unsupported escape sequence");
2605     }
2606 
2607     /**
2608      * Parse a character class, and return the node that matches it.
2609      *
2610      * Consumes a ] on the way out if consume is true. Usually consume
2611      * is true except for the case of [abc&&def] where def is a separate
2612      * right hand node with "understood" brackets.
2613      */
2614     private CharPredicate clazz(boolean consume) {
2615         CharPredicate prev = null;
2616         CharPredicate curr = null;
2617         BitClass bits = new BitClass();
2618         BmpCharPredicate bitsP = ch -> ch < 256 && bits.bits[ch];
2619 
2620         boolean isNeg = false;
2621         boolean hasBits = false;
2622         int ch = next();
2623 
2624         // Negates if first char in a class, otherwise literal
2625         if (ch == '^' && temp[cursor-1] == '[') {
2626             ch = next();
2627             isNeg = true;
2628         }
2629         for (;;) {
2630             switch (ch) {
2631                 case '[':
2632                     curr = clazz(true);
2633                     if (prev == null)
2634                         prev = curr;
2635                     else
2636                         prev = prev.union(curr);
2637                     ch = peek();
2638                     continue;
2639                 case '&':
2640                     ch = next();
2641                     if (ch == '&') {
2642                         ch = next();
2643                         CharPredicate right = null;
2644                         while (ch != ']' && ch != '&') {
2645                             if (ch == '[') {
2646                                 if (right == null)
2647                                     right = clazz(true);
2648                                 else
2649                                     right = right.union(clazz(true));
2650                             } else { // abc&&def
2651                                 unread();
2652                                 right = clazz(false);
2653                             }
2654                             ch = peek();
2655                         }
2656                         if (hasBits) {
2657                             // bits used, union has high precedence
2658                             if (prev == null) {
2659                                 prev = curr = bitsP;
2660                             } else {
2661                                 prev = prev.union(bitsP);
2662                             }
2663                             hasBits = false;
2664                         }
2665                         if (right != null)
2666                             curr = right;
2667                         if (prev == null) {
2668                             if (right == null)
2669                                 throw error("Bad class syntax");
2670                             else
2671                                 prev = right;
2672                         } else {
2673                             prev = prev.and(curr);
2674                         }
2675                     } else {
2676                         // treat as a literal &
2677                         unread();
2678                         break;
2679                     }
2680                     continue;
2681                 case 0:
2682                     if (cursor >= patternLength)
2683                         throw error("Unclosed character class");
2684                     break;
2685                 case ']':
2686                     if (prev != null || hasBits) {
2687                         if (consume)
2688                             next();
2689                         if (prev == null)
2690                             prev = bitsP;
2691                         else if (hasBits)
2692                             prev = prev.union(bitsP);
2693                         if (isNeg)
2694                             return prev.negate();
2695                         return prev;
2696                     }
2697                     break;
2698                 default:
2699                     break;
2700             }
2701             curr = range(bits);
2702             if (curr == null) {    // the bits used
2703                 hasBits = true;
2704             } else {
2705                 if (prev == null)
2706                     prev = curr;
2707                 else if (prev != curr)
2708                     prev = prev.union(curr);
2709             }
2710             ch = peek();
2711         }
2712     }
2713 
2714     private CharPredicate bitsOrSingle(BitClass bits, int ch) {
2715         /* Bits can only handle codepoints in [u+0000-u+00ff] range.
2716            Use "single" node instead of bits when dealing with unicode
2717            case folding for codepoints listed below.
2718            (1)Uppercase out of range: u+00ff, u+00b5
2719               toUpperCase(u+00ff) -> u+0178
2720               toUpperCase(u+00b5) -> u+039c
2721            (2)LatinSmallLetterLongS u+17f
2722               toUpperCase(u+017f) -> u+0053
2723            (3)LatinSmallLetterDotlessI u+131
2724               toUpperCase(u+0131) -> u+0049
2725            (4)LatinCapitalLetterIWithDotAbove u+0130
2726               toLowerCase(u+0130) -> u+0069
2727            (5)KelvinSign u+212a
2728               toLowerCase(u+212a) ==> u+006B
2729            (6)AngstromSign u+212b
2730               toLowerCase(u+212b) ==> u+00e5
2731         */
2732         if (ch < 256 &&
2733             !(has(CASE_INSENSITIVE) && has(UNICODE_CASE) &&
2734               (ch == 0xff || ch == 0xb5 ||
2735                ch == 0x49 || ch == 0x69 ||    //I and i
2736                ch == 0x53 || ch == 0x73 ||    //S and s
2737                ch == 0x4b || ch == 0x6b ||    //K and k
2738                ch == 0xc5 || ch == 0xe5))) {  //A+ring
2739             bits.add(ch, flags0);
2740             return null;
2741         }
2742         return single(ch);
2743     }
2744 
2745     /**
2746      *  Returns a suitably optimized, single character predicate
2747      */
2748     private CharPredicate single(final int ch) {
2749         if (has(CASE_INSENSITIVE)) {
2750             int lower, upper;
2751             if (has(UNICODE_CASE)) {
2752                 upper = Character.toUpperCase(ch);
2753                 lower = Character.toLowerCase(upper);
2754                 // Unicode case insensitive matches
2755                 if (upper != lower)
2756                     return SingleU(lower);
2757             } else if (ASCII.isAscii(ch)) {
2758                 lower = ASCII.toLower(ch);
2759                 upper = ASCII.toUpper(ch);
2760                 // Case insensitive matches a given BMP character
2761                 if (lower != upper)
2762                     return SingleI(lower, upper);
2763             }
2764         }
2765         if (isSupplementary(ch))
2766             return SingleS(ch);
2767         return Single(ch);  // Match a given BMP character
2768     }
2769 
2770     /**
2771      * Parse a single character or a character range in a character class
2772      * and return its representative node.
2773      */
2774     private CharPredicate range(BitClass bits) {
2775         int ch = peek();
2776         if (ch == '\\') {
2777             ch = nextEscaped();
2778             if (ch == 'p' || ch == 'P') { // A property
2779                 boolean comp = (ch == 'P');
2780                 boolean oneLetter = true;
2781                 // Consume { if present
2782                 ch = next();
2783                 if (ch != '{')
2784                     unread();
2785                 else
2786                     oneLetter = false;
2787                 return family(oneLetter, comp);
2788             } else { // ordinary escape
2789                 boolean isrange = temp[cursor+1] == '-';
2790                 unread();
2791                 ch = escape(true, true, isrange);
2792                 if (ch == -1)
2793                     return predicate;
2794             }
2795         } else {
2796             next();
2797         }
2798         if (ch >= 0) {
2799             if (peek() == '-') {
2800                 int endRange = temp[cursor+1];
2801                 if (endRange == '[') {
2802                     return bitsOrSingle(bits, ch);
2803                 }
2804                 if (endRange != ']') {
2805                     next();
2806                     int m = peek();
2807                     if (m == '\\') {
2808                         m = escape(true, false, true);
2809                     } else {
2810                         next();
2811                     }
2812                     if (m < ch) {
2813                         throw error("Illegal character range");
2814                     }
2815                     if (has(CASE_INSENSITIVE)) {
2816                         if (has(UNICODE_CASE))
2817                             return CIRangeU(ch, m);
2818                         return CIRange(ch, m);
2819                     } else {
2820                         return Range(ch, m);
2821                     }
2822                 }
2823             }
2824             return bitsOrSingle(bits, ch);
2825         }
2826         throw error("Unexpected character '"+((char)ch)+"'");
2827     }
2828 
2829     /**
2830      * Parses a Unicode character family and returns its representative node.
2831      */
2832     private CharPredicate family(boolean singleLetter, boolean isComplement) {
2833         next();
2834         String name;
2835         CharPredicate p = null;
2836 
2837         if (singleLetter) {
2838             int c = temp[cursor];
2839             if (!Character.isSupplementaryCodePoint(c)) {
2840                 name = String.valueOf((char)c);
2841             } else {
2842                 name = new String(temp, cursor, 1);
2843             }
2844             read();
2845         } else {
2846             int i = cursor;
2847             mark('}');
2848             while(read() != '}') {
2849             }
2850             mark('\000');
2851             int j = cursor;
2852             if (j > patternLength)
2853                 throw error("Unclosed character family");
2854             if (i + 1 >= j)
2855                 throw error("Empty character family");
2856             name = new String(temp, i, j-i-1);
2857         }
2858 
2859         int i = name.indexOf('=');
2860         if (i != -1) {
2861             // property construct \p{name=value}
2862             String value = name.substring(i + 1);
2863             name = name.substring(0, i).toLowerCase(Locale.ENGLISH);
2864             switch (name) {
2865                 case "sc":
2866                 case "script":
2867                     p = CharPredicates.forUnicodeScript(value);
2868                     break;
2869                 case "blk":
2870                 case "block":
2871                     p = CharPredicates.forUnicodeBlock(value);
2872                     break;
2873                 case "gc":
2874                 case "general_category":
2875                     p = CharPredicates.forProperty(value);
2876                     break;
2877                 default:
2878                     break;
2879             }
2880             if (p == null)
2881                 throw error("Unknown Unicode property {name=<" + name + ">, "
2882                              + "value=<" + value + ">}");
2883 
2884         } else {
2885             if (name.startsWith("In")) {
2886                 // \p{InBlockName}
2887                 p = CharPredicates.forUnicodeBlock(name.substring(2));
2888             } else if (name.startsWith("Is")) {
2889                 // \p{IsGeneralCategory} and \p{IsScriptName}
2890                 name = name.substring(2);
2891                 p = CharPredicates.forUnicodeProperty(name);
2892                 if (p == null)
2893                     p = CharPredicates.forProperty(name);
2894                 if (p == null)
2895                     p = CharPredicates.forUnicodeScript(name);
2896             } else {
2897                 if (has(UNICODE_CHARACTER_CLASS)) {
2898                     p = CharPredicates.forPOSIXName(name);
2899                 }
2900                 if (p == null)
2901                     p = CharPredicates.forProperty(name);
2902             }
2903             if (p == null)
2904                 throw error("Unknown character property name {In/Is" + name + "}");
2905         }
2906         if (isComplement) {
2907             // it might be too expensive to detect if a complement of
2908             // CharProperty can match "certain" supplementary. So just
2909             // go with StartS.
2910             hasSupplementary = true;
2911             p = p.negate();
2912         }
2913         return p;
2914     }
2915 
2916     private CharProperty newCharProperty(CharPredicate p) {
2917         if (p == null)
2918             return null;
2919         if (p instanceof BmpCharPredicate)
2920             return new BmpCharProperty((BmpCharPredicate)p);
2921         else
2922             return new CharProperty(p);
2923     }
2924 
2925     /**
2926      * Parses and returns the name of a "named capturing group", the trailing
2927      * ">" is consumed after parsing.
2928      */
2929     private String groupname(int ch) {
2930         StringBuilder sb = new StringBuilder();
2931         if (!ASCII.isAlpha(ch))
2932             throw error("capturing group name does not start with a Latin letter");
2933         do {
2934             sb.append((char) ch);
2935         } while (ASCII.isAlnum(ch=read()));
2936         if (ch != '>')
2937             throw error("named capturing group is missing trailing '>'");
2938         return sb.toString();
2939     }
2940 
2941     /**
2942      * Parses a group and returns the head node of a set of nodes that process
2943      * the group. Sometimes a double return system is used where the tail is
2944      * returned in root.
2945      */
2946     private Node group0() {
2947         boolean capturingGroup = false;
2948         Node head = null;
2949         Node tail = null;
2950         int save = flags0;
2951         int saveTCNCount = topClosureNodes.size();
2952         root = null;
2953         int ch = next();
2954         if (ch == '?') {
2955             ch = skip();
2956             switch (ch) {
2957             case ':':   //  (?:xxx) pure group
2958                 head = createGroup(true);
2959                 tail = root;
2960                 head.next = expr(tail);
2961                 break;
2962             case '=':   // (?=xxx) and (?!xxx) lookahead
2963             case '!':
2964                 head = createGroup(true);
2965                 tail = root;
2966                 head.next = expr(tail);
2967                 if (ch == '=') {
2968                     head = tail = new Pos(head);
2969                 } else {
2970                     head = tail = new Neg(head);
2971                 }
2972                 break;
2973             case '>':   // (?>xxx)  independent group
2974                 head = createGroup(true);
2975                 tail = root;
2976                 head.next = expr(tail);
2977                 head = tail = new Ques(head, Qtype.INDEPENDENT);
2978                 break;
2979             case '<':   // (?<xxx)  look behind
2980                 ch = read();
2981                 if (ch != '=' && ch != '!') {
2982                     // named captured group
2983                     String name = groupname(ch);
2984                     if (namedGroups().containsKey(name))
2985                         throw error("Named capturing group <" + name
2986                                     + "> is already defined");
2987                     capturingGroup = true;
2988                     head = createGroup(false);
2989                     tail = root;
2990                     namedGroups().put(name, capturingGroupCount-1);
2991                     head.next = expr(tail);
2992                     break;
2993                 }
2994                 int start = cursor;
2995                 head = createGroup(true);
2996                 tail = root;
2997                 head.next = expr(tail);
2998                 tail.next = lookbehindEnd;
2999                 TreeInfo info = new TreeInfo();
3000                 head.study(info);
3001                 if (info.maxValid == false) {
3002                     throw error("Look-behind group does not have "
3003                                 + "an obvious maximum length");
3004                 }
3005                 boolean hasSupplementary = findSupplementary(start, patternLength);
3006                 if (ch == '=') {
3007                     head = tail = (hasSupplementary ?
3008                                    new BehindS(head, info.maxLength,
3009                                                info.minLength) :
3010                                    new Behind(head, info.maxLength,
3011                                               info.minLength));
3012                 } else { // if (ch == '!')
3013                     head = tail = (hasSupplementary ?
3014                                    new NotBehindS(head, info.maxLength,
3015                                                   info.minLength) :
3016                                    new NotBehind(head, info.maxLength,
3017                                                  info.minLength));
3018                 }
3019                 // clear all top-closure-nodes inside lookbehind
3020                 if (saveTCNCount < topClosureNodes.size())
3021                     topClosureNodes.subList(saveTCNCount, topClosureNodes.size()).clear();
3022                 break;
3023             case '$':
3024             case '@':
3025                 throw error("Unknown group type");
3026             default:    // (?xxx:) inlined match flags
3027                 unread();
3028                 addFlag();
3029                 ch = read();
3030                 if (ch == ')') {
3031                     return null;    // Inline modifier only
3032                 }
3033                 if (ch != ':') {
3034                     throw error("Unknown inline modifier");
3035                 }
3036                 head = createGroup(true);
3037                 tail = root;
3038                 head.next = expr(tail);
3039                 break;
3040             }
3041         } else { // (xxx) a regular group
3042             capturingGroup = true;
3043             head = createGroup(false);
3044             tail = root;
3045             head.next = expr(tail);
3046         }
3047 
3048         accept(')', "Unclosed group");
3049         flags0 = save;
3050 
3051         // Check for quantifiers
3052         Node node = closure(head);
3053         if (node == head) { // No closure
3054             root = tail;
3055             return node;    // Dual return
3056         }
3057         if (head == tail) { // Zero length assertion
3058             root = node;
3059             return node;    // Dual return
3060         }
3061 
3062         // have group closure, clear all inner closure nodes from the
3063         // top list (no backtracking stopper optimization for inner
3064         if (saveTCNCount < topClosureNodes.size())
3065             topClosureNodes.subList(saveTCNCount, topClosureNodes.size()).clear();
3066 
3067         if (node instanceof Ques) {
3068             Ques ques = (Ques) node;
3069             if (ques.type == Qtype.POSSESSIVE) {
3070                 root = node;
3071                 return node;
3072             }
3073             tail.next = new BranchConn();
3074             tail = tail.next;
3075             if (ques.type == Qtype.GREEDY) {
3076                 head = new Branch(head, null, tail);
3077             } else { // Reluctant quantifier
3078                 head = new Branch(null, head, tail);
3079             }
3080             root = tail;
3081             return head;
3082         } else if (node instanceof Curly) {
3083             Curly curly = (Curly) node;
3084             if (curly.type == Qtype.POSSESSIVE) {
3085                 root = node;
3086                 return node;
3087             }
3088             // Discover if the group is deterministic
3089             TreeInfo info = new TreeInfo();
3090             if (head.study(info)) { // Deterministic
3091                 GroupTail temp = (GroupTail) tail;
3092                 head = root = new GroupCurly(head.next, curly.cmin,
3093                                    curly.cmax, curly.type,
3094                                    ((GroupTail)tail).localIndex,
3095                                    ((GroupTail)tail).groupIndex,
3096                                              capturingGroup);
3097                 return head;
3098             } else { // Non-deterministic
3099                 int temp = ((GroupHead) head).localIndex;
3100                 Loop loop;
3101                 if (curly.type == Qtype.GREEDY) {
3102                     loop = new Loop(this.localCount, temp);
3103                     // add the max_reps greedy to the top-closure-node list
3104                     if (curly.cmax == MAX_REPS)
3105                         topClosureNodes.add(loop);
3106                 } else {  // Reluctant Curly
3107                     loop = new LazyLoop(this.localCount, temp);
3108                 }
3109                 Prolog prolog = new Prolog(loop);
3110                 this.localCount += 1;
3111                 loop.cmin = curly.cmin;
3112                 loop.cmax = curly.cmax;
3113                 loop.body = head;
3114                 tail.next = loop;
3115                 root = loop;
3116                 return prolog; // Dual return
3117             }
3118         }
3119         throw error("Internal logic error");
3120     }
3121 
3122     /**
3123      * Create group head and tail nodes using double return. If the group is
3124      * created with anonymous true then it is a pure group and should not
3125      * affect group counting.
3126      */
3127     private Node createGroup(boolean anonymous) {
3128         int localIndex = localCount++;
3129         int groupIndex = 0;
3130         if (!anonymous)
3131             groupIndex = capturingGroupCount++;
3132         GroupHead head = new GroupHead(localIndex);
3133         root = new GroupTail(localIndex, groupIndex);
3134 
3135         // for debug/print only, head.match does NOT need the "tail" info
3136         head.tail = (GroupTail)root;
3137 
3138         if (!anonymous && groupIndex < 10)
3139             groupNodes[groupIndex] = head;
3140         return head;
3141     }
3142 
3143     @SuppressWarnings("fallthrough")
3144     /**
3145      * Parses inlined match flags and set them appropriately.
3146      */
3147     private void addFlag() {
3148         int ch = peek();
3149         for (;;) {
3150             switch (ch) {
3151             case 'i':
3152                 flags0 |= CASE_INSENSITIVE;
3153                 break;
3154             case 'm':
3155                 flags0 |= MULTILINE;
3156                 break;
3157             case 's':
3158                 flags0 |= DOTALL;
3159                 break;
3160             case 'd':
3161                 flags0 |= UNIX_LINES;
3162                 break;
3163             case 'u':
3164                 flags0 |= UNICODE_CASE;
3165                 break;
3166             case 'c':
3167                 flags0 |= CANON_EQ;
3168                 break;
3169             case 'x':
3170                 flags0 |= COMMENTS;
3171                 break;
3172             case 'U':
3173                 flags0 |= (UNICODE_CHARACTER_CLASS | UNICODE_CASE);
3174                 break;
3175             case '-': // subFlag then fall through
3176                 ch = next();
3177                 subFlag();
3178             default:
3179                 return;
3180             }
3181             ch = next();
3182         }
3183     }
3184 
3185     @SuppressWarnings("fallthrough")
3186     /**
3187      * Parses the second part of inlined match flags and turns off
3188      * flags appropriately.
3189      */
3190     private void subFlag() {
3191         int ch = peek();
3192         for (;;) {
3193             switch (ch) {
3194             case 'i':
3195                 flags0 &= ~CASE_INSENSITIVE;
3196                 break;
3197             case 'm':
3198                 flags0 &= ~MULTILINE;
3199                 break;
3200             case 's':
3201                 flags0 &= ~DOTALL;
3202                 break;
3203             case 'd':
3204                 flags0 &= ~UNIX_LINES;
3205                 break;
3206             case 'u':
3207                 flags0 &= ~UNICODE_CASE;
3208                 break;
3209             case 'c':
3210                 flags0 &= ~CANON_EQ;
3211                 break;
3212             case 'x':
3213                 flags0 &= ~COMMENTS;
3214                 break;
3215             case 'U':
3216                 flags0 &= ~(UNICODE_CHARACTER_CLASS | UNICODE_CASE);
3217                 break;
3218             default:
3219                 return;
3220             }
3221             ch = next();
3222         }
3223     }
3224 
3225     static final int MAX_REPS   = 0x7FFFFFFF;
3226 
3227     static enum Qtype {
3228         GREEDY, LAZY, POSSESSIVE, INDEPENDENT
3229     }
3230 
3231     private Node curly(Node prev, int cmin) {
3232         int ch = next();
3233         if (ch == '?') {
3234             next();
3235             return new Curly(prev, cmin, MAX_REPS, Qtype.LAZY);
3236         } else if (ch == '+') {
3237             next();
3238             return new Curly(prev, cmin, MAX_REPS, Qtype.POSSESSIVE);
3239         }
3240         if (prev instanceof BmpCharProperty) {
3241             return new BmpCharPropertyGreedy((BmpCharProperty)prev, cmin);
3242         } else if (prev instanceof CharProperty) {
3243             return new CharPropertyGreedy((CharProperty)prev, cmin);
3244         }
3245         return new Curly(prev, cmin, MAX_REPS, Qtype.GREEDY);
3246     }
3247 
3248     /**
3249      * Processes repetition. If the next character peeked is a quantifier
3250      * then new nodes must be appended to handle the repetition.
3251      * Prev could be a single or a group, so it could be a chain of nodes.
3252      */
3253     private Node closure(Node prev) {
3254         Node atom;
3255         int ch = peek();
3256         switch (ch) {
3257         case '?':
3258             ch = next();
3259             if (ch == '?') {
3260                 next();
3261                 return new Ques(prev, Qtype.LAZY);
3262             } else if (ch == '+') {
3263                 next();
3264                 return new Ques(prev, Qtype.POSSESSIVE);
3265             }
3266             return new Ques(prev, Qtype.GREEDY);
3267         case '*':
3268             return curly(prev, 0);
3269         case '+':
3270             return curly(prev, 1);
3271         case '{':
3272             ch = temp[cursor+1];
3273             if (ASCII.isDigit(ch)) {
3274                 skip();
3275                 int cmin = 0;
3276                 do {
3277                     cmin = cmin * 10 + (ch - '0');
3278                 } while (ASCII.isDigit(ch = read()));
3279                 int cmax = cmin;
3280                 if (ch == ',') {
3281                     ch = read();
3282                     cmax = MAX_REPS;
3283                     if (ch != '}') {
3284                         cmax = 0;
3285                         while (ASCII.isDigit(ch)) {
3286                             cmax = cmax * 10 + (ch - '0');
3287                             ch = read();
3288                         }
3289                     }
3290                 }
3291                 if (ch != '}')
3292                     throw error("Unclosed counted closure");
3293                 if (((cmin) | (cmax) | (cmax - cmin)) < 0)
3294                     throw error("Illegal repetition range");
3295                 Curly curly;
3296                 ch = peek();
3297                 if (ch == '?') {
3298                     next();
3299                     curly = new Curly(prev, cmin, cmax, Qtype.LAZY);
3300                 } else if (ch == '+') {
3301                     next();
3302                     curly = new Curly(prev, cmin, cmax, Qtype.POSSESSIVE);
3303                 } else {
3304                     curly = new Curly(prev, cmin, cmax, Qtype.GREEDY);
3305                 }
3306                 return curly;
3307             } else {
3308                 throw error("Illegal repetition");
3309             }
3310         default:
3311             return prev;
3312         }
3313     }
3314 
3315     /**
3316      *  Utility method for parsing control escape sequences.
3317      */
3318     private int c() {
3319         if (cursor < patternLength) {
3320             return read() ^ 64;
3321         }
3322         throw error("Illegal control escape sequence");
3323     }
3324 
3325     /**
3326      *  Utility method for parsing octal escape sequences.
3327      */
3328     private int o() {
3329         int n = read();
3330         if (((n-'0')|('7'-n)) >= 0) {
3331             int m = read();
3332             if (((m-'0')|('7'-m)) >= 0) {
3333                 int o = read();
3334                 if ((((o-'0')|('7'-o)) >= 0) && (((n-'0')|('3'-n)) >= 0)) {
3335                     return (n - '0') * 64 + (m - '0') * 8 + (o - '0');
3336                 }
3337                 unread();
3338                 return (n - '0') * 8 + (m - '0');
3339             }
3340             unread();
3341             return (n - '0');
3342         }
3343         throw error("Illegal octal escape sequence");
3344     }
3345 
3346     /**
3347      *  Utility method for parsing hexadecimal escape sequences.
3348      */
3349     private int x() {
3350         int n = read();
3351         if (ASCII.isHexDigit(n)) {
3352             int m = read();
3353             if (ASCII.isHexDigit(m)) {
3354                 return ASCII.toDigit(n) * 16 + ASCII.toDigit(m);
3355             }
3356         } else if (n == '{' && ASCII.isHexDigit(peek())) {
3357             int ch = 0;
3358             while (ASCII.isHexDigit(n = read())) {
3359                 ch = (ch << 4) + ASCII.toDigit(n);
3360                 if (ch > Character.MAX_CODE_POINT)
3361                     throw error("Hexadecimal codepoint is too big");
3362             }
3363             if (n != '}')
3364                 throw error("Unclosed hexadecimal escape sequence");
3365             return ch;
3366         }
3367         throw error("Illegal hexadecimal escape sequence");
3368     }
3369 
3370     /**
3371      *  Utility method for parsing unicode escape sequences.
3372      */
3373     private int cursor() {
3374         return cursor;
3375     }
3376 
3377     private void setcursor(int pos) {
3378         cursor = pos;
3379     }
3380 
3381     private int uxxxx() {
3382         int n = 0;
3383         for (int i = 0; i < 4; i++) {
3384             int ch = read();
3385             if (!ASCII.isHexDigit(ch)) {
3386                 throw error("Illegal Unicode escape sequence");
3387             }
3388             n = n * 16 + ASCII.toDigit(ch);
3389         }
3390         return n;
3391     }
3392 
3393     private int u() {
3394         int n = uxxxx();
3395         if (Character.isHighSurrogate((char)n)) {
3396             int cur = cursor();
3397             if (read() == '\\' && read() == 'u') {
3398                 int n2 = uxxxx();
3399                 if (Character.isLowSurrogate((char)n2))
3400                     return Character.toCodePoint((char)n, (char)n2);
3401             }
3402             setcursor(cur);
3403         }
3404         return n;
3405     }
3406 
3407     private int N() {
3408         if (read() == '{') {
3409             int i = cursor;
3410             while (cursor < patternLength && read() != '}') {}
3411             if (cursor > patternLength)
3412                 throw error("Unclosed character name escape sequence");
3413             String name = new String(temp, i, cursor - i - 1);
3414             try {
3415                 return Character.codePointOf(name);
3416             } catch (IllegalArgumentException x) {
3417                 throw error("Unknown character name [" + name + "]");
3418             }
3419         }
3420         throw error("Illegal character name escape sequence");
3421     }
3422 
3423     //
3424     // Utility methods for code point support
3425     //
3426     private static final int countChars(CharSequence seq, int index,
3427                                         int lengthInCodePoints) {
3428         // optimization
3429         if (lengthInCodePoints == 1 && !Character.isHighSurrogate(seq.charAt(index))) {
3430             assert (index >= 0 && index < seq.length());
3431             return 1;
3432         }
3433         int length = seq.length();
3434         int x = index;
3435         if (lengthInCodePoints >= 0) {
3436             assert (index >= 0 && index < length);
3437             for (int i = 0; x < length && i < lengthInCodePoints; i++) {
3438                 if (Character.isHighSurrogate(seq.charAt(x++))) {
3439                     if (x < length && Character.isLowSurrogate(seq.charAt(x))) {
3440                         x++;
3441                     }
3442                 }
3443             }
3444             return x - index;
3445         }
3446 
3447         assert (index >= 0 && index <= length);
3448         if (index == 0) {
3449             return 0;
3450         }
3451         int len = -lengthInCodePoints;
3452         for (int i = 0; x > 0 && i < len; i++) {
3453             if (Character.isLowSurrogate(seq.charAt(--x))) {
3454                 if (x > 0 && Character.isHighSurrogate(seq.charAt(x-1))) {
3455                     x--;
3456                 }
3457             }
3458         }
3459         return index - x;
3460     }
3461 
3462     private static final int countCodePoints(CharSequence seq) {
3463         int length = seq.length();
3464         int n = 0;
3465         for (int i = 0; i < length; ) {
3466             n++;
3467             if (Character.isHighSurrogate(seq.charAt(i++))) {
3468                 if (i < length && Character.isLowSurrogate(seq.charAt(i))) {
3469                     i++;
3470                 }
3471             }
3472         }
3473         return n;
3474     }
3475 
3476     /**
3477      *  Creates a bit vector for matching Latin-1 values. A normal BitClass
3478      *  never matches values above Latin-1, and a complemented BitClass always
3479      *  matches values above Latin-1.
3480      */
3481     static final class BitClass extends BmpCharProperty {
3482         final boolean[] bits;
3483         BitClass() {
3484             this(new boolean[256]);
3485         }
3486         private BitClass(boolean[] bits) {
3487             super( ch -> ch < 256 && bits[ch]);
3488             this.bits = bits;
3489         }
3490         BitClass add(int c, int flags) {
3491             assert c >= 0 && c <= 255;
3492             if ((flags & CASE_INSENSITIVE) != 0) {
3493                 if (ASCII.isAscii(c)) {
3494                     bits[ASCII.toUpper(c)] = true;
3495                     bits[ASCII.toLower(c)] = true;
3496                 } else if ((flags & UNICODE_CASE) != 0) {
3497                     bits[Character.toLowerCase(c)] = true;
3498                     bits[Character.toUpperCase(c)] = true;
3499                 }
3500             }
3501             bits[c] = true;
3502             return this;
3503         }
3504     }
3505 
3506     /**
3507      *  Utility method for creating a string slice matcher.
3508      */
3509     private Node newSlice(int[] buf, int count, boolean hasSupplementary) {
3510         int[] tmp = new int[count];
3511         if (has(CASE_INSENSITIVE)) {
3512             if (has(UNICODE_CASE)) {
3513                 for (int i = 0; i < count; i++) {
3514                     tmp[i] = Character.toLowerCase(
3515                                  Character.toUpperCase(buf[i]));
3516                 }
3517                 return hasSupplementary? new SliceUS(tmp) : new SliceU(tmp);
3518             }
3519             for (int i = 0; i < count; i++) {
3520                 tmp[i] = ASCII.toLower(buf[i]);
3521             }
3522             return hasSupplementary? new SliceIS(tmp) : new SliceI(tmp);
3523         }
3524         for (int i = 0; i < count; i++) {
3525             tmp[i] = buf[i];
3526         }
3527         return hasSupplementary ? new SliceS(tmp) : new Slice(tmp);
3528     }
3529 
3530     /**
3531      * The following classes are the building components of the object
3532      * tree that represents a compiled regular expression. The object tree
3533      * is made of individual elements that handle constructs in the Pattern.
3534      * Each type of object knows how to match its equivalent construct with
3535      * the match() method.
3536      */
3537 
3538     /**
3539      * Base class for all node classes. Subclasses should override the match()
3540      * method as appropriate. This class is an accepting node, so its match()
3541      * always returns true.
3542      */
3543     static class Node extends Object {
3544         Node next;
3545         Node() {
3546             next = Pattern.accept;
3547         }
3548         /**
3549          * This method implements the classic accept node.
3550          */
3551         boolean match(Matcher matcher, int i, CharSequence seq) {
3552             matcher.last = i;
3553             matcher.groups[0] = matcher.first;
3554             matcher.groups[1] = matcher.last;
3555             return true;
3556         }
3557         /**
3558          * This method is good for all zero length assertions.
3559          */
3560         boolean study(TreeInfo info) {
3561             if (next != null) {
3562                 return next.study(info);
3563             } else {
3564                 return info.deterministic;
3565             }
3566         }
3567     }
3568 
3569     static class LastNode extends Node {
3570         /**
3571          * This method implements the classic accept node with
3572          * the addition of a check to see if the match occurred
3573          * using all of the input.
3574          */
3575         boolean match(Matcher matcher, int i, CharSequence seq) {
3576             if (matcher.acceptMode == Matcher.ENDANCHOR && i != matcher.to)
3577                 return false;
3578             matcher.last = i;
3579             matcher.groups[0] = matcher.first;
3580             matcher.groups[1] = matcher.last;
3581             return true;
3582         }
3583     }
3584 
3585     /**
3586      * Used for REs that can start anywhere within the input string.
3587      * This basically tries to match repeatedly at each spot in the
3588      * input string, moving forward after each try. An anchored search
3589      * or a BnM will bypass this node completely.
3590      */
3591     static class Start extends Node {
3592         int minLength;
3593         Start(Node node) {
3594             this.next = node;
3595             TreeInfo info = new TreeInfo();
3596             next.study(info);
3597             minLength = info.minLength;
3598         }
3599         boolean match(Matcher matcher, int i, CharSequence seq) {
3600             if (i > matcher.to - minLength) {
3601                 matcher.hitEnd = true;
3602                 return false;
3603             }
3604             int guard = matcher.to - minLength;
3605             for (; i <= guard; i++) {
3606                 if (next.match(matcher, i, seq)) {
3607                     matcher.first = i;
3608                     matcher.groups[0] = matcher.first;
3609                     matcher.groups[1] = matcher.last;
3610                     return true;
3611                 }
3612             }
3613             matcher.hitEnd = true;
3614             return false;
3615         }
3616         boolean study(TreeInfo info) {
3617             next.study(info);
3618             info.maxValid = false;
3619             info.deterministic = false;
3620             return false;
3621         }
3622     }
3623 
3624     /*
3625      * StartS supports supplementary characters, including unpaired surrogates.
3626      */
3627     static final class StartS extends Start {
3628         StartS(Node node) {
3629             super(node);
3630         }
3631         boolean match(Matcher matcher, int i, CharSequence seq) {
3632             if (i > matcher.to - minLength) {
3633                 matcher.hitEnd = true;
3634                 return false;
3635             }
3636             int guard = matcher.to - minLength;
3637             while (i <= guard) {
3638                 //if ((ret = next.match(matcher, i, seq)) || i == guard)
3639                 if (next.match(matcher, i, seq)) {
3640                     matcher.first = i;
3641                     matcher.groups[0] = matcher.first;
3642                     matcher.groups[1] = matcher.last;
3643                     return true;
3644                 }
3645                 if (i == guard)
3646                     break;
3647                 // Optimization to move to the next character. This is
3648                 // faster than countChars(seq, i, 1).
3649                 if (Character.isHighSurrogate(seq.charAt(i++))) {
3650                     if (i < seq.length() &&
3651                         Character.isLowSurrogate(seq.charAt(i))) {
3652                         i++;
3653                     }
3654                 }
3655             }
3656             matcher.hitEnd = true;
3657             return false;
3658         }
3659     }
3660 
3661     /**
3662      * Node to anchor at the beginning of input. This object implements the
3663      * match for a \A sequence, and the caret anchor will use this if not in
3664      * multiline mode.
3665      */
3666     static final class Begin extends Node {
3667         boolean match(Matcher matcher, int i, CharSequence seq) {
3668             int fromIndex = (matcher.anchoringBounds) ?
3669                 matcher.from : 0;
3670             if (i == fromIndex && next.match(matcher, i, seq)) {
3671                 matcher.first = i;
3672                 matcher.groups[0] = i;
3673                 matcher.groups[1] = matcher.last;
3674                 return true;
3675             } else {
3676                 return false;
3677             }
3678         }
3679     }
3680 
3681     /**
3682      * Node to anchor at the end of input. This is the absolute end, so this
3683      * should not match at the last newline before the end as $ will.
3684      */
3685     static final class End extends Node {
3686         boolean match(Matcher matcher, int i, CharSequence seq) {
3687             int endIndex = (matcher.anchoringBounds) ?
3688                 matcher.to : matcher.getTextLength();
3689             if (i == endIndex) {
3690                 matcher.hitEnd = true;
3691                 return next.match(matcher, i, seq);
3692             }
3693             return false;
3694         }
3695     }
3696 
3697     /**
3698      * Node to anchor at the beginning of a line. This is essentially the
3699      * object to match for the multiline ^.
3700      */
3701     static final class Caret extends Node {
3702         boolean match(Matcher matcher, int i, CharSequence seq) {
3703             int startIndex = matcher.from;
3704             int endIndex = matcher.to;
3705             if (!matcher.anchoringBounds) {
3706                 startIndex = 0;
3707                 endIndex = matcher.getTextLength();
3708             }
3709             // Perl does not match ^ at end of input even after newline
3710             if (i == endIndex) {
3711                 matcher.hitEnd = true;
3712                 return false;
3713             }
3714             if (i > startIndex) {
3715                 char ch = seq.charAt(i-1);
3716                 if (ch != '\n' && ch != '\r'
3717                     && (ch|1) != '\u2029'
3718                     && ch != '\u0085' ) {
3719                     return false;
3720                 }
3721                 // Should treat /r/n as one newline
3722                 if (ch == '\r' && seq.charAt(i) == '\n')
3723                     return false;
3724             }
3725             return next.match(matcher, i, seq);
3726         }
3727     }
3728 
3729     /**
3730      * Node to anchor at the beginning of a line when in unixdot mode.
3731      */
3732     static final class UnixCaret extends Node {
3733         boolean match(Matcher matcher, int i, CharSequence seq) {
3734             int startIndex = matcher.from;
3735             int endIndex = matcher.to;
3736             if (!matcher.anchoringBounds) {
3737                 startIndex = 0;
3738                 endIndex = matcher.getTextLength();
3739             }
3740             // Perl does not match ^ at end of input even after newline
3741             if (i == endIndex) {
3742                 matcher.hitEnd = true;
3743                 return false;
3744             }
3745             if (i > startIndex) {
3746                 char ch = seq.charAt(i-1);
3747                 if (ch != '\n') {
3748                     return false;
3749                 }
3750             }
3751             return next.match(matcher, i, seq);
3752         }
3753     }
3754 
3755     /**
3756      * Node to match the location where the last match ended.
3757      * This is used for the \G construct.
3758      */
3759     static final class LastMatch extends Node {
3760         boolean match(Matcher matcher, int i, CharSequence seq) {
3761             if (i != matcher.oldLast)
3762                 return false;
3763             return next.match(matcher, i, seq);
3764         }
3765     }
3766 
3767     /**
3768      * Node to anchor at the end of a line or the end of input based on the
3769      * multiline mode.
3770      *
3771      * When not in multiline mode, the $ can only match at the very end
3772      * of the input, unless the input ends in a line terminator in which
3773      * it matches right before the last line terminator.
3774      *
3775      * Note that \r\n is considered an atomic line terminator.
3776      *
3777      * Like ^ the $ operator matches at a position, it does not match the
3778      * line terminators themselves.
3779      */
3780     static final class Dollar extends Node {
3781         boolean multiline;
3782         Dollar(boolean mul) {
3783             multiline = mul;
3784         }
3785         boolean match(Matcher matcher, int i, CharSequence seq) {
3786             int endIndex = (matcher.anchoringBounds) ?
3787                 matcher.to : matcher.getTextLength();
3788             if (!multiline) {
3789                 if (i < endIndex - 2)
3790                     return false;
3791                 if (i == endIndex - 2) {
3792                     char ch = seq.charAt(i);
3793                     if (ch != '\r')
3794                         return false;
3795                     ch = seq.charAt(i + 1);
3796                     if (ch != '\n')
3797                         return false;
3798                 }
3799             }
3800             // Matches before any line terminator; also matches at the
3801             // end of input
3802             // Before line terminator:
3803             // If multiline, we match here no matter what
3804             // If not multiline, fall through so that the end
3805             // is marked as hit; this must be a /r/n or a /n
3806             // at the very end so the end was hit; more input
3807             // could make this not match here
3808             if (i < endIndex) {
3809                 char ch = seq.charAt(i);
3810                  if (ch == '\n') {
3811                      // No match between \r\n
3812                      if (i > 0 && seq.charAt(i-1) == '\r')
3813                          return false;
3814                      if (multiline)
3815                          return next.match(matcher, i, seq);
3816                  } else if (ch == '\r' || ch == '\u0085' ||
3817                             (ch|1) == '\u2029') {
3818                      if (multiline)
3819                          return next.match(matcher, i, seq);
3820                  } else { // No line terminator, no match
3821                      return false;
3822                  }
3823             }
3824             // Matched at current end so hit end
3825             matcher.hitEnd = true;
3826             // If a $ matches because of end of input, then more input
3827             // could cause it to fail!
3828             matcher.requireEnd = true;
3829             return next.match(matcher, i, seq);
3830         }
3831         boolean study(TreeInfo info) {
3832             next.study(info);
3833             return info.deterministic;
3834         }
3835     }
3836 
3837     /**
3838      * Node to anchor at the end of a line or the end of input based on the
3839      * multiline mode when in unix lines mode.
3840      */
3841     static final class UnixDollar extends Node {
3842         boolean multiline;
3843         UnixDollar(boolean mul) {
3844             multiline = mul;
3845         }
3846         boolean match(Matcher matcher, int i, CharSequence seq) {
3847             int endIndex = (matcher.anchoringBounds) ?
3848                 matcher.to : matcher.getTextLength();
3849             if (i < endIndex) {
3850                 char ch = seq.charAt(i);
3851                 if (ch == '\n') {
3852                     // If not multiline, then only possible to
3853                     // match at very end or one before end
3854                     if (multiline == false && i != endIndex - 1)
3855                         return false;
3856                     // If multiline return next.match without setting
3857                     // matcher.hitEnd
3858                     if (multiline)
3859                         return next.match(matcher, i, seq);
3860                 } else {
3861                     return false;
3862                 }
3863             }
3864             // Matching because at the end or 1 before the end;
3865             // more input could change this so set hitEnd
3866             matcher.hitEnd = true;
3867             // If a $ matches because of end of input, then more input
3868             // could cause it to fail!
3869             matcher.requireEnd = true;
3870             return next.match(matcher, i, seq);
3871         }
3872         boolean study(TreeInfo info) {
3873             next.study(info);
3874             return info.deterministic;
3875         }
3876     }
3877 
3878     /**
3879      * Node class that matches a Unicode line ending '\R'
3880      */
3881     static final class LineEnding extends Node {
3882         boolean match(Matcher matcher, int i, CharSequence seq) {
3883             // (u+000Du+000A|[u+000Au+000Bu+000Cu+000Du+0085u+2028u+2029])
3884             if (i < matcher.to) {
3885                 int ch = seq.charAt(i);
3886                 if (ch == 0x0A || ch == 0x0B || ch == 0x0C ||
3887                     ch == 0x85 || ch == 0x2028 || ch == 0x2029)
3888                     return next.match(matcher, i + 1, seq);
3889                 if (ch == 0x0D) {
3890                     i++;
3891                     if (i < matcher.to) {
3892                         if (seq.charAt(i) == 0x0A &&
3893                             next.match(matcher, i + 1, seq)) {
3894                             return true;
3895                         }
3896                     } else {
3897                         matcher.hitEnd = true;
3898                     }
3899                     return next.match(matcher, i, seq);
3900                 }
3901             } else {
3902                 matcher.hitEnd = true;
3903             }
3904             return false;
3905         }
3906         boolean study(TreeInfo info) {
3907             info.minLength++;
3908             info.maxLength += 2;
3909             return next.study(info);
3910         }
3911     }
3912 
3913     /**
3914      * Abstract node class to match one character satisfying some
3915      * boolean property.
3916      */
3917     static class CharProperty extends Node {
3918         CharPredicate predicate;
3919 
3920         CharProperty (CharPredicate predicate) {
3921             this.predicate = predicate;
3922         }
3923         boolean match(Matcher matcher, int i, CharSequence seq) {
3924             if (i < matcher.to) {
3925                 int ch = Character.codePointAt(seq, i);
3926                 return predicate.is(ch) &&
3927                        next.match(matcher, i + Character.charCount(ch), seq);
3928             } else {
3929                 matcher.hitEnd = true;
3930                 return false;
3931             }
3932         }
3933         boolean study(TreeInfo info) {
3934             info.minLength++;
3935             info.maxLength++;
3936             return next.study(info);
3937         }
3938     }
3939 
3940     /**
3941      * Optimized version of CharProperty that works only for
3942      * properties never satisfied by Supplementary characters.
3943      */
3944     private static class BmpCharProperty extends CharProperty {
3945         BmpCharProperty (BmpCharPredicate predicate) {
3946             super(predicate);
3947         }
3948         boolean match(Matcher matcher, int i, CharSequence seq) {
3949             if (i < matcher.to) {
3950                 return predicate.is(seq.charAt(i)) &&
3951                        next.match(matcher, i + 1, seq);
3952             } else {
3953                 matcher.hitEnd = true;
3954                 return false;
3955             }
3956         }
3957     }
3958 
3959     private static class NFCCharProperty extends Node {
3960         CharPredicate predicate;
3961         NFCCharProperty (CharPredicate predicate) {
3962             this.predicate = predicate;
3963         }
3964 
3965         boolean match(Matcher matcher, int i, CharSequence seq) {
3966             if (i < matcher.to) {
3967                 int ch0 = Character.codePointAt(seq, i);
3968                 int n = Character.charCount(ch0);
3969                 int j = i + n;
3970                 while (j < matcher.to) {
3971                     int ch1 = Character.codePointAt(seq, j);
3972                     if (Grapheme.isBoundary(ch0, ch1))
3973                         break;
3974                     ch0 = ch1;
3975                     j += Character.charCount(ch1);
3976                 }
3977                 if (i + n == j) {    // single, assume nfc cp
3978                     if (predicate.is(ch0))
3979                         return next.match(matcher, j, seq);
3980                 } else {
3981                     while (i + n < j) {
3982                         String nfc = Normalizer.normalize(
3983                             seq.toString().substring(i, j), Normalizer.Form.NFC);
3984                         if (nfc.codePointCount(0, nfc.length()) == 1) {
3985                             if (predicate.is(nfc.codePointAt(0)) &&
3986                                 next.match(matcher, j, seq)) {
3987                                 return true;
3988                             }
3989                         }
3990 
3991                         ch0 = Character.codePointBefore(seq, j);
3992                         j -= Character.charCount(ch0);
3993                     }
3994                 }
3995                 if (j < matcher.to)
3996                     return false;
3997             }
3998             matcher.hitEnd = true;
3999             return false;
4000         }
4001 
4002         boolean study(TreeInfo info) {
4003             info.minLength++;
4004             info.deterministic = false;
4005             return next.study(info);
4006         }
4007     }
4008 
4009     /**
4010      * Node class that matches an unicode extended grapheme cluster
4011      */
4012     static class XGrapheme extends Node {
4013         boolean match(Matcher matcher, int i, CharSequence seq) {
4014             if (i < matcher.to) {
4015                 int ch0 = Character.codePointAt(seq, i);
4016                     i += Character.charCount(ch0);
4017                 while (i < matcher.to) {
4018                     int ch1 = Character.codePointAt(seq, i);
4019                     if (Grapheme.isBoundary(ch0, ch1))
4020                         break;
4021                     ch0 = ch1;
4022                     i += Character.charCount(ch1);
4023                 }
4024                 return next.match(matcher, i, seq);
4025             }
4026             matcher.hitEnd = true;
4027             return false;
4028         }
4029 
4030         boolean study(TreeInfo info) {
4031             info.minLength++;
4032             info.deterministic = false;
4033             return next.study(info);
4034         }
4035     }
4036 
4037     /**
4038      * Node class that handles grapheme boundaries
4039      */
4040     static class GraphemeBound extends Node {
4041         boolean match(Matcher matcher, int i, CharSequence seq) {
4042             int startIndex = matcher.from;
4043             int endIndex = matcher.to;
4044             if (matcher.transparentBounds) {
4045                 startIndex = 0;
4046                 endIndex = matcher.getTextLength();
4047             }
4048             if (i == startIndex) {
4049                 return next.match(matcher, i, seq);
4050             }
4051             if (i < endIndex) {
4052                 if (Character.isSurrogatePair(seq.charAt(i-1), seq.charAt(i)) ||
4053                     !Grapheme.isBoundary(Character.codePointBefore(seq, i),
4054                                          Character.codePointAt(seq, i))) {
4055                     return false;
4056                 }
4057             } else {
4058                 matcher.hitEnd = true;
4059                 matcher.requireEnd = true;
4060             }
4061             return next.match(matcher, i, seq);
4062         }
4063     }
4064 
4065     /**
4066      * Base class for all Slice nodes
4067      */
4068     static class SliceNode extends Node {
4069         int[] buffer;
4070         SliceNode(int[] buf) {
4071             buffer = buf;
4072         }
4073         boolean study(TreeInfo info) {
4074             info.minLength += buffer.length;
4075             info.maxLength += buffer.length;
4076             return next.study(info);
4077         }
4078     }
4079 
4080     /**
4081      * Node class for a case sensitive/BMP-only sequence of literal
4082      * characters.
4083      */
4084     static class Slice extends SliceNode {
4085         Slice(int[] buf) {
4086             super(buf);
4087         }
4088         boolean match(Matcher matcher, int i, CharSequence seq) {
4089             int[] buf = buffer;
4090             int len = buf.length;
4091             for (int j=0; j<len; j++) {
4092                 if ((i+j) >= matcher.to) {
4093                     matcher.hitEnd = true;
4094                     return false;
4095                 }
4096                 if (buf[j] != seq.charAt(i+j))
4097                     return false;
4098             }
4099             return next.match(matcher, i+len, seq);
4100         }
4101     }
4102 
4103     /**
4104      * Node class for a case_insensitive/BMP-only sequence of literal
4105      * characters.
4106      */
4107     static class SliceI extends SliceNode {
4108         SliceI(int[] buf) {
4109             super(buf);
4110         }
4111         boolean match(Matcher matcher, int i, CharSequence seq) {
4112             int[] buf = buffer;
4113             int len = buf.length;
4114             for (int j=0; j<len; j++) {
4115                 if ((i+j) >= matcher.to) {
4116                     matcher.hitEnd = true;
4117                     return false;
4118                 }
4119                 int c = seq.charAt(i+j);
4120                 if (buf[j] != c &&
4121                     buf[j] != ASCII.toLower(c))
4122                     return false;
4123             }
4124             return next.match(matcher, i+len, seq);
4125         }
4126     }
4127 
4128     /**
4129      * Node class for a unicode_case_insensitive/BMP-only sequence of
4130      * literal characters. Uses unicode case folding.
4131      */
4132     static final class SliceU extends SliceNode {
4133         SliceU(int[] buf) {
4134             super(buf);
4135         }
4136         boolean match(Matcher matcher, int i, CharSequence seq) {
4137             int[] buf = buffer;
4138             int len = buf.length;
4139             for (int j=0; j<len; j++) {
4140                 if ((i+j) >= matcher.to) {
4141                     matcher.hitEnd = true;
4142                     return false;
4143                 }
4144                 int c = seq.charAt(i+j);
4145                 if (buf[j] != c &&
4146                     buf[j] != Character.toLowerCase(Character.toUpperCase(c)))
4147                     return false;
4148             }
4149             return next.match(matcher, i+len, seq);
4150         }
4151     }
4152 
4153     /**
4154      * Node class for a case sensitive sequence of literal characters
4155      * including supplementary characters.
4156      */
4157     static final class SliceS extends Slice {
4158         SliceS(int[] buf) {
4159             super(buf);
4160         }
4161         boolean match(Matcher matcher, int i, CharSequence seq) {
4162             int[] buf = buffer;
4163             int x = i;
4164             for (int j = 0; j < buf.length; j++) {
4165                 if (x >= matcher.to) {
4166                     matcher.hitEnd = true;
4167                     return false;
4168                 }
4169                 int c = Character.codePointAt(seq, x);
4170                 if (buf[j] != c)
4171                     return false;
4172                 x += Character.charCount(c);
4173                 if (x > matcher.to) {
4174                     matcher.hitEnd = true;
4175                     return false;
4176                 }
4177             }
4178             return next.match(matcher, x, seq);
4179         }
4180     }
4181 
4182     /**
4183      * Node class for a case insensitive sequence of literal characters
4184      * including supplementary characters.
4185      */
4186     static class SliceIS extends SliceNode {
4187         SliceIS(int[] buf) {
4188             super(buf);
4189         }
4190         int toLower(int c) {
4191             return ASCII.toLower(c);
4192         }
4193         boolean match(Matcher matcher, int i, CharSequence seq) {
4194             int[] buf = buffer;
4195             int x = i;
4196             for (int j = 0; j < buf.length; j++) {
4197                 if (x >= matcher.to) {
4198                     matcher.hitEnd = true;
4199                     return false;
4200                 }
4201                 int c = Character.codePointAt(seq, x);
4202                 if (buf[j] != c && buf[j] != toLower(c))
4203                     return false;
4204                 x += Character.charCount(c);
4205                 if (x > matcher.to) {
4206                     matcher.hitEnd = true;
4207                     return false;
4208                 }
4209             }
4210             return next.match(matcher, x, seq);
4211         }
4212     }
4213 
4214     /**
4215      * Node class for a case insensitive sequence of literal characters.
4216      * Uses unicode case folding.
4217      */
4218     static final class SliceUS extends SliceIS {
4219         SliceUS(int[] buf) {
4220             super(buf);
4221         }
4222         int toLower(int c) {
4223             return Character.toLowerCase(Character.toUpperCase(c));
4224         }
4225     }
4226 
4227     /**
4228      * The 0 or 1 quantifier. This one class implements all three types.
4229      */
4230     static final class Ques extends Node {
4231         Node atom;
4232         Qtype type;
4233         Ques(Node node, Qtype type) {
4234             this.atom = node;
4235             this.type = type;
4236         }
4237         boolean match(Matcher matcher, int i, CharSequence seq) {
4238             switch (type) {
4239             case GREEDY:
4240                 return (atom.match(matcher, i, seq) && next.match(matcher, matcher.last, seq))
4241                     || next.match(matcher, i, seq);
4242             case LAZY:
4243                 return next.match(matcher, i, seq)
4244                     || (atom.match(matcher, i, seq) && next.match(matcher, matcher.last, seq));
4245             case POSSESSIVE:
4246                 if (atom.match(matcher, i, seq)) i = matcher.last;
4247                 return next.match(matcher, i, seq);
4248             default:
4249                 return atom.match(matcher, i, seq) && next.match(matcher, matcher.last, seq);
4250             }
4251         }
4252         boolean study(TreeInfo info) {
4253             if (type != Qtype.INDEPENDENT) {
4254                 int minL = info.minLength;
4255                 atom.study(info);
4256                 info.minLength = minL;
4257                 info.deterministic = false;
4258                 return next.study(info);
4259             } else {
4260                 atom.study(info);
4261                 return next.study(info);
4262             }
4263         }
4264     }
4265 
4266     /**
4267      * Handles the greedy style repetition with the minimum either be
4268      * 0 or 1 and the maximum be MAX_REPS, for * and + quantifier.
4269      */
4270     static class CharPropertyGreedy extends Node {
4271         final CharPredicate predicate;
4272         final int cmin;
4273 
4274         CharPropertyGreedy(CharProperty cp, int cmin) {
4275             this.predicate = cp.predicate;
4276             this.cmin = cmin;
4277         }
4278         boolean match(Matcher matcher, int i,  CharSequence seq) {
4279             int n = 0;
4280             int to = matcher.to;
4281             // greedy, all the way down
4282             while (i < to) {
4283                 int ch = Character.codePointAt(seq, i);
4284                 if (!predicate.is(ch))
4285                    break;
4286                 i += Character.charCount(ch);
4287                 n++;
4288             }
4289             if (i >= to) {
4290                 matcher.hitEnd = true;
4291             }
4292             while (n >= cmin) {
4293                 if (next.match(matcher, i, seq))
4294                     return true;
4295                 if (n == cmin)
4296                     return false;
4297                  // backing off if match fails
4298                 int ch = Character.codePointBefore(seq, i);
4299                 i -= Character.charCount(ch);
4300                 n--;
4301             }
4302             return false;
4303         }
4304 
4305         boolean study(TreeInfo info) {
4306             info.minLength += cmin;
4307             if (info.maxValid) {
4308                 info.maxLength += MAX_REPS;
4309             }
4310             info.deterministic = false;
4311             return next.study(info);
4312         }
4313     }
4314 
4315     static final class BmpCharPropertyGreedy extends CharPropertyGreedy {
4316 
4317         BmpCharPropertyGreedy(BmpCharProperty bcp, int cmin) {
4318             super(bcp, cmin);
4319         }
4320 
4321         boolean match(Matcher matcher, int i,  CharSequence seq) {
4322             int n = 0;
4323             int to = matcher.to;
4324             while (i < to && predicate.is(seq.charAt(i))) {
4325                 i++; n++;
4326             }
4327             if (i >= to) {
4328                 matcher.hitEnd = true;
4329             }
4330             while (n >= cmin) {
4331                 if (next.match(matcher, i, seq))
4332                     return true;
4333                 i--; n--;  // backing off if match fails
4334             }
4335             return false;
4336         }
4337     }
4338 
4339     /**
4340      * Handles the curly-brace style repetition with a specified minimum and
4341      * maximum occurrences. The * quantifier is handled as a special case.
4342      * This class handles the three types.
4343      */
4344     static final class Curly extends Node {
4345         Node atom;
4346         Qtype type;
4347         int cmin;
4348         int cmax;
4349 
4350         Curly(Node node, int cmin, int cmax, Qtype type) {
4351             this.atom = node;
4352             this.type = type;
4353             this.cmin = cmin;
4354             this.cmax = cmax;
4355         }
4356         boolean match(Matcher matcher, int i, CharSequence seq) {
4357             int j;
4358             for (j = 0; j < cmin; j++) {
4359                 if (atom.match(matcher, i, seq)) {
4360                     i = matcher.last;
4361                     continue;
4362                 }
4363                 return false;
4364             }
4365             if (type == Qtype.GREEDY)
4366                 return match0(matcher, i, j, seq);
4367             else if (type == Qtype.LAZY)
4368                 return match1(matcher, i, j, seq);
4369             else
4370                 return match2(matcher, i, j, seq);
4371         }
4372         // Greedy match.
4373         // i is the index to start matching at
4374         // j is the number of atoms that have matched
4375         boolean match0(Matcher matcher, int i, int j, CharSequence seq) {
4376             if (j >= cmax) {
4377                 // We have matched the maximum... continue with the rest of
4378                 // the regular expression
4379                 return next.match(matcher, i, seq);
4380             }
4381             int backLimit = j;
4382             while (atom.match(matcher, i, seq)) {
4383                 // k is the length of this match
4384                 int k = matcher.last - i;
4385                 if (k == 0) // Zero length match
4386                     break;
4387                 // Move up index and number matched
4388                 i = matcher.last;
4389                 j++;
4390                 // We are greedy so match as many as we can
4391                 while (j < cmax) {
4392                     if (!atom.match(matcher, i, seq))
4393                         break;
4394                     if (i + k != matcher.last) {
4395                         if (match0(matcher, matcher.last, j+1, seq))
4396                             return true;
4397                         break;
4398                     }
4399                     i += k;
4400                     j++;
4401                 }
4402                 // Handle backing off if match fails
4403                 while (j >= backLimit) {
4404                    if (next.match(matcher, i, seq))
4405                         return true;
4406                     i -= k;
4407                     j--;
4408                 }
4409                 return false;
4410             }
4411             return next.match(matcher, i, seq);
4412         }
4413         // Reluctant match. At this point, the minimum has been satisfied.
4414         // i is the index to start matching at
4415         // j is the number of atoms that have matched
4416         boolean match1(Matcher matcher, int i, int j, CharSequence seq) {
4417             for (;;) {
4418                 // Try finishing match without consuming any more
4419                 if (next.match(matcher, i, seq))
4420                     return true;
4421                 // At the maximum, no match found
4422                 if (j >= cmax)
4423                     return false;
4424                 // Okay, must try one more atom
4425                 if (!atom.match(matcher, i, seq))
4426                     return false;
4427                 // If we haven't moved forward then must break out
4428                 if (i == matcher.last)
4429                     return false;
4430                 // Move up index and number matched
4431                 i = matcher.last;
4432                 j++;
4433             }
4434         }
4435         boolean match2(Matcher matcher, int i, int j, CharSequence seq) {
4436             for (; j < cmax; j++) {
4437                 if (!atom.match(matcher, i, seq))
4438                     break;
4439                 if (i == matcher.last)
4440                     break;
4441                 i = matcher.last;
4442             }
4443             return next.match(matcher, i, seq);
4444         }
4445         boolean study(TreeInfo info) {
4446             // Save original info
4447             int minL = info.minLength;
4448             int maxL = info.maxLength;
4449             boolean maxV = info.maxValid;
4450             boolean detm = info.deterministic;
4451             info.reset();
4452 
4453             atom.study(info);
4454 
4455             int temp = info.minLength * cmin + minL;
4456             if (temp < minL) {
4457                 temp = 0xFFFFFFF; // arbitrary large number
4458             }
4459             info.minLength = temp;
4460 
4461             if (maxV & info.maxValid) {
4462                 temp = info.maxLength * cmax + maxL;
4463                 info.maxLength = temp;
4464                 if (temp < maxL) {
4465                     info.maxValid = false;
4466                 }
4467             } else {
4468                 info.maxValid = false;
4469             }
4470 
4471             if (info.deterministic && cmin == cmax)
4472                 info.deterministic = detm;
4473             else
4474                 info.deterministic = false;
4475             return next.study(info);
4476         }
4477     }
4478 
4479     /**
4480      * Handles the curly-brace style repetition with a specified minimum and
4481      * maximum occurrences in deterministic cases. This is an iterative
4482      * optimization over the Prolog and Loop system which would handle this
4483      * in a recursive way. The * quantifier is handled as a special case.
4484      * If capture is true then this class saves group settings and ensures
4485      * that groups are unset when backing off of a group match.
4486      */
4487     static final class GroupCurly extends Node {
4488         Node atom;
4489         Qtype type;
4490         int cmin;
4491         int cmax;
4492         int localIndex;
4493         int groupIndex;
4494         boolean capture;
4495 
4496         GroupCurly(Node node, int cmin, int cmax, Qtype type, int local,
4497                    int group, boolean capture) {
4498             this.atom = node;
4499             this.type = type;
4500             this.cmin = cmin;
4501             this.cmax = cmax;
4502             this.localIndex = local;
4503             this.groupIndex = group;
4504             this.capture = capture;
4505         }
4506         boolean match(Matcher matcher, int i, CharSequence seq) {
4507             int[] groups = matcher.groups;
4508             int[] locals = matcher.locals;
4509             int save0 = locals[localIndex];
4510             int save1 = 0;
4511             int save2 = 0;
4512 
4513             if (capture) {
4514                 save1 = groups[groupIndex];
4515                 save2 = groups[groupIndex+1];
4516             }
4517 
4518             // Notify GroupTail there is no need to setup group info
4519             // because it will be set here
4520             locals[localIndex] = -1;
4521 
4522             boolean ret = true;
4523             for (int j = 0; j < cmin; j++) {
4524                 if (atom.match(matcher, i, seq)) {
4525                     if (capture) {
4526                         groups[groupIndex] = i;
4527                         groups[groupIndex+1] = matcher.last;
4528                     }
4529                     i = matcher.last;
4530                 } else {
4531                     ret = false;
4532                     break;
4533                 }
4534             }
4535             if (ret) {
4536                 if (type == Qtype.GREEDY) {
4537                     ret = match0(matcher, i, cmin, seq);
4538                 } else if (type == Qtype.LAZY) {
4539                     ret = match1(matcher, i, cmin, seq);
4540                 } else {
4541                     ret = match2(matcher, i, cmin, seq);
4542                 }
4543             }
4544             if (!ret) {
4545                 locals[localIndex] = save0;
4546                 if (capture) {
4547                     groups[groupIndex] = save1;
4548                     groups[groupIndex+1] = save2;
4549                 }
4550             }
4551             return ret;
4552         }
4553         // Aggressive group match
4554         boolean match0(Matcher matcher, int i, int j, CharSequence seq) {
4555             // don't back off passing the starting "j"
4556             int min = j;
4557             int[] groups = matcher.groups;
4558             int save0 = 0;
4559             int save1 = 0;
4560             if (capture) {
4561                 save0 = groups[groupIndex];
4562                 save1 = groups[groupIndex+1];
4563             }
4564             for (;;) {
4565                 if (j >= cmax)
4566                     break;
4567                 if (!atom.match(matcher, i, seq))
4568                     break;
4569                 int k = matcher.last - i;
4570                 if (k <= 0) {
4571                     if (capture) {
4572                         groups[groupIndex] = i;
4573                         groups[groupIndex+1] = i + k;
4574                     }
4575                     i = i + k;
4576                     break;
4577                 }
4578                 for (;;) {
4579                     if (capture) {
4580                         groups[groupIndex] = i;
4581                         groups[groupIndex+1] = i + k;
4582                     }
4583                     i = i + k;
4584                     if (++j >= cmax)
4585                         break;
4586                     if (!atom.match(matcher, i, seq))
4587                         break;
4588                     if (i + k != matcher.last) {
4589                         if (match0(matcher, i, j, seq))
4590                             return true;
4591                         break;
4592                     }
4593                 }
4594                 while (j > min) {
4595                     if (next.match(matcher, i, seq)) {
4596                         if (capture) {
4597                             groups[groupIndex+1] = i;
4598                             groups[groupIndex] = i - k;
4599                         }
4600                         return true;
4601                     }
4602                     // backing off
4603                     i = i - k;
4604                     if (capture) {
4605                         groups[groupIndex+1] = i;
4606                         groups[groupIndex] = i - k;
4607                     }
4608                     j--;
4609 
4610                 }
4611                 break;
4612             }
4613             if (capture) {
4614                 groups[groupIndex] = save0;
4615                 groups[groupIndex+1] = save1;
4616             }
4617             return next.match(matcher, i, seq);
4618         }
4619         // Reluctant matching
4620         boolean match1(Matcher matcher, int i, int j, CharSequence seq) {
4621             for (;;) {
4622                 if (next.match(matcher, i, seq))
4623                     return true;
4624                 if (j >= cmax)
4625                     return false;
4626                 if (!atom.match(matcher, i, seq))
4627                     return false;
4628                 if (i == matcher.last)
4629                     return false;
4630                 if (capture) {
4631                     matcher.groups[groupIndex] = i;
4632                     matcher.groups[groupIndex+1] = matcher.last;
4633                 }
4634                 i = matcher.last;
4635                 j++;
4636             }
4637         }
4638         // Possessive matching
4639         boolean match2(Matcher matcher, int i, int j, CharSequence seq) {
4640             for (; j < cmax; j++) {
4641                 if (!atom.match(matcher, i, seq)) {
4642                     break;
4643                 }
4644                 if (capture) {
4645                     matcher.groups[groupIndex] = i;
4646                     matcher.groups[groupIndex+1] = matcher.last;
4647                 }
4648                 if (i == matcher.last) {
4649                     break;
4650                 }
4651                 i = matcher.last;
4652             }
4653             return next.match(matcher, i, seq);
4654         }
4655         boolean study(TreeInfo info) {
4656             // Save original info
4657             int minL = info.minLength;
4658             int maxL = info.maxLength;
4659             boolean maxV = info.maxValid;
4660             boolean detm = info.deterministic;
4661             info.reset();
4662 
4663             atom.study(info);
4664 
4665             int temp = info.minLength * cmin + minL;
4666             if (temp < minL) {
4667                 temp = 0xFFFFFFF; // Arbitrary large number
4668             }
4669             info.minLength = temp;
4670 
4671             if (maxV & info.maxValid) {
4672                 temp = info.maxLength * cmax + maxL;
4673                 info.maxLength = temp;
4674                 if (temp < maxL) {
4675                     info.maxValid = false;
4676                 }
4677             } else {
4678                 info.maxValid = false;
4679             }
4680 
4681             if (info.deterministic && cmin == cmax) {
4682                 info.deterministic = detm;
4683             } else {
4684                 info.deterministic = false;
4685             }
4686             return next.study(info);
4687         }
4688     }
4689 
4690     /**
4691      * A Guard node at the end of each atom node in a Branch. It
4692      * serves the purpose of chaining the "match" operation to
4693      * "next" but not the "study", so we can collect the TreeInfo
4694      * of each atom node without including the TreeInfo of the
4695      * "next".
4696      */
4697     static final class BranchConn extends Node {
4698         BranchConn() {};
4699         boolean match(Matcher matcher, int i, CharSequence seq) {
4700             return next.match(matcher, i, seq);
4701         }
4702         boolean study(TreeInfo info) {
4703             return info.deterministic;
4704         }
4705     }
4706 
4707     /**
4708      * Handles the branching of alternations. Note this is also used for
4709      * the ? quantifier to branch between the case where it matches once
4710      * and where it does not occur.
4711      */
4712     static final class Branch extends Node {
4713         Node[] atoms = new Node[2];
4714         int size = 2;
4715         Node conn;
4716         Branch(Node first, Node second, Node branchConn) {
4717             conn = branchConn;
4718             atoms[0] = first;
4719             atoms[1] = second;
4720         }
4721 
4722         void add(Node node) {
4723             if (size >= atoms.length) {
4724                 Node[] tmp = new Node[atoms.length*2];
4725                 System.arraycopy(atoms, 0, tmp, 0, atoms.length);
4726                 atoms = tmp;
4727             }
4728             atoms[size++] = node;
4729         }
4730 
4731         boolean match(Matcher matcher, int i, CharSequence seq) {
4732             for (int n = 0; n < size; n++) {
4733                 if (atoms[n] == null) {
4734                     if (conn.next.match(matcher, i, seq))
4735                         return true;
4736                 } else if (atoms[n].match(matcher, i, seq)) {
4737                     return true;
4738                 }
4739             }
4740             return false;
4741         }
4742 
4743         boolean study(TreeInfo info) {
4744             int minL = info.minLength;
4745             int maxL = info.maxLength;
4746             boolean maxV = info.maxValid;
4747 
4748             int minL2 = Integer.MAX_VALUE; //arbitrary large enough num
4749             int maxL2 = -1;
4750             for (int n = 0; n < size; n++) {
4751                 info.reset();
4752                 if (atoms[n] != null)
4753                     atoms[n].study(info);
4754                 minL2 = Math.min(minL2, info.minLength);
4755                 maxL2 = Math.max(maxL2, info.maxLength);
4756                 maxV = (maxV & info.maxValid);
4757             }
4758 
4759             minL += minL2;
4760             maxL += maxL2;
4761 
4762             info.reset();
4763             conn.next.study(info);
4764 
4765             info.minLength += minL;
4766             info.maxLength += maxL;
4767             info.maxValid &= maxV;
4768             info.deterministic = false;
4769             return false;
4770         }
4771     }
4772 
4773     /**
4774      * The GroupHead saves the location where the group begins in the locals
4775      * and restores them when the match is done.
4776      *
4777      * The matchRef is used when a reference to this group is accessed later
4778      * in the expression. The locals will have a negative value in them to
4779      * indicate that we do not want to unset the group if the reference
4780      * doesn't match.
4781      */
4782     static final class GroupHead extends Node {
4783         int localIndex;
4784         GroupTail tail;    // for debug/print only, match does not need to know
4785         GroupHead(int localCount) {
4786             localIndex = localCount;
4787         }
4788         boolean match(Matcher matcher, int i, CharSequence seq) {
4789             int save = matcher.locals[localIndex];
4790             matcher.locals[localIndex] = i;
4791             boolean ret = next.match(matcher, i, seq);
4792             matcher.locals[localIndex] = save;
4793             return ret;
4794         }
4795         boolean matchRef(Matcher matcher, int i, CharSequence seq) {
4796             int save = matcher.locals[localIndex];
4797             matcher.locals[localIndex] = ~i; // HACK
4798             boolean ret = next.match(matcher, i, seq);
4799             matcher.locals[localIndex] = save;
4800             return ret;
4801         }
4802     }
4803 
4804     /**
4805      * Recursive reference to a group in the regular expression. It calls
4806      * matchRef because if the reference fails to match we would not unset
4807      * the group.
4808      */
4809     static final class GroupRef extends Node {
4810         GroupHead head;
4811         GroupRef(GroupHead head) {
4812             this.head = head;
4813         }
4814         boolean match(Matcher matcher, int i, CharSequence seq) {
4815             return head.matchRef(matcher, i, seq)
4816                 && next.match(matcher, matcher.last, seq);
4817         }
4818         boolean study(TreeInfo info) {
4819             info.maxValid = false;
4820             info.deterministic = false;
4821             return next.study(info);
4822         }
4823     }
4824 
4825     /**
4826      * The GroupTail handles the setting of group beginning and ending
4827      * locations when groups are successfully matched. It must also be able to
4828      * unset groups that have to be backed off of.
4829      *
4830      * The GroupTail node is also used when a previous group is referenced,
4831      * and in that case no group information needs to be set.
4832      */
4833     static final class GroupTail extends Node {
4834         int localIndex;
4835         int groupIndex;
4836         GroupTail(int localCount, int groupCount) {
4837             localIndex = localCount;
4838             groupIndex = groupCount + groupCount;
4839         }
4840         boolean match(Matcher matcher, int i, CharSequence seq) {
4841             int tmp = matcher.locals[localIndex];
4842             if (tmp >= 0) { // This is the normal group case.
4843                 // Save the group so we can unset it if it
4844                 // backs off of a match.
4845                 int groupStart = matcher.groups[groupIndex];
4846                 int groupEnd = matcher.groups[groupIndex+1];
4847 
4848                 matcher.groups[groupIndex] = tmp;
4849                 matcher.groups[groupIndex+1] = i;
4850                 if (next.match(matcher, i, seq)) {
4851                     return true;
4852                 }
4853                 matcher.groups[groupIndex] = groupStart;
4854                 matcher.groups[groupIndex+1] = groupEnd;
4855                 return false;
4856             } else {
4857                 // This is a group reference case. We don't need to save any
4858                 // group info because it isn't really a group.
4859                 matcher.last = i;
4860                 return true;
4861             }
4862         }
4863     }
4864 
4865     /**
4866      * This sets up a loop to handle a recursive quantifier structure.
4867      */
4868     static final class Prolog extends Node {
4869         Loop loop;
4870         Prolog(Loop loop) {
4871             this.loop = loop;
4872         }
4873         boolean match(Matcher matcher, int i, CharSequence seq) {
4874             return loop.matchInit(matcher, i, seq);
4875         }
4876         boolean study(TreeInfo info) {
4877             return loop.study(info);
4878         }
4879     }
4880 
4881     /**
4882      * Handles the repetition count for a greedy Curly. The matchInit
4883      * is called from the Prolog to save the index of where the group
4884      * beginning is stored. A zero length group check occurs in the
4885      * normal match but is skipped in the matchInit.
4886      */
4887     static class Loop extends Node {
4888         Node body;
4889         int countIndex; // local count index in matcher locals
4890         int beginIndex; // group beginning index
4891         int cmin, cmax;
4892         int posIndex;
4893         Loop(int countIndex, int beginIndex) {
4894             this.countIndex = countIndex;
4895             this.beginIndex = beginIndex;
4896             this.posIndex = -1;
4897         }
4898         boolean match(Matcher matcher, int i, CharSequence seq) {
4899             // Avoid infinite loop in zero-length case.
4900             if (i > matcher.locals[beginIndex]) {
4901                 int count = matcher.locals[countIndex];
4902 
4903                 // This block is for before we reach the minimum
4904                 // iterations required for the loop to match
4905                 if (count < cmin) {
4906                     matcher.locals[countIndex] = count + 1;
4907                     boolean b = body.match(matcher, i, seq);
4908                     // If match failed we must backtrack, so
4909                     // the loop count should NOT be incremented
4910                     if (!b)
4911                         matcher.locals[countIndex] = count;
4912                     // Return success or failure since we are under
4913                     // minimum
4914                     return b;
4915                 }
4916                 // This block is for after we have the minimum
4917                 // iterations required for the loop to match
4918                 if (count < cmax) {
4919                     // Let's check if we have already tried and failed
4920                     // at this starting position "i" in the past.
4921                     // If yes, then just return false wihtout trying
4922                     // again, to stop the exponential backtracking.
4923                     if (posIndex != -1 &&
4924                         matcher.localsPos[posIndex].contains(i)) {
4925                         return next.match(matcher, i, seq);
4926                     }
4927                     matcher.locals[countIndex] = count + 1;
4928                     boolean b = body.match(matcher, i, seq);
4929                     // If match failed we must backtrack, so
4930                     // the loop count should NOT be incremented
4931                     if (b)
4932                         return true;
4933                     matcher.locals[countIndex] = count;
4934                     // save the failed position
4935                     if (posIndex != -1) {
4936                         matcher.localsPos[posIndex].add(i);
4937                     }
4938                 }
4939             }
4940             return next.match(matcher, i, seq);
4941         }
4942         boolean matchInit(Matcher matcher, int i, CharSequence seq) {
4943             int save = matcher.locals[countIndex];
4944             boolean ret = false;
4945             if (posIndex != -1 && matcher.localsPos[posIndex] == null) {
4946                 matcher.localsPos[posIndex] = new IntHashSet();
4947             }
4948             if (0 < cmin) {
4949                 matcher.locals[countIndex] = 1;
4950                 ret = body.match(matcher, i, seq);
4951             } else if (0 < cmax) {
4952                 matcher.locals[countIndex] = 1;
4953                 ret = body.match(matcher, i, seq);
4954                 if (ret == false)
4955                     ret = next.match(matcher, i, seq);
4956             } else {
4957                 ret = next.match(matcher, i, seq);
4958             }
4959             matcher.locals[countIndex] = save;
4960             return ret;
4961         }
4962         boolean study(TreeInfo info) {
4963             info.maxValid = false;
4964             info.deterministic = false;
4965             return false;
4966         }
4967     }
4968 
4969     /**
4970      * Handles the repetition count for a reluctant Curly. The matchInit
4971      * is called from the Prolog to save the index of where the group
4972      * beginning is stored. A zero length group check occurs in the
4973      * normal match but is skipped in the matchInit.
4974      */
4975     static final class LazyLoop extends Loop {
4976         LazyLoop(int countIndex, int beginIndex) {
4977             super(countIndex, beginIndex);
4978         }
4979         boolean match(Matcher matcher, int i, CharSequence seq) {
4980             // Check for zero length group
4981             if (i > matcher.locals[beginIndex]) {
4982                 int count = matcher.locals[countIndex];
4983                 if (count < cmin) {
4984                     matcher.locals[countIndex] = count + 1;
4985                     boolean result = body.match(matcher, i, seq);
4986                     // If match failed we must backtrack, so
4987                     // the loop count should NOT be incremented
4988                     if (!result)
4989                         matcher.locals[countIndex] = count;
4990                     return result;
4991                 }
4992                 if (next.match(matcher, i, seq))
4993                     return true;
4994                 if (count < cmax) {
4995                     matcher.locals[countIndex] = count + 1;
4996                     boolean result = body.match(matcher, i, seq);
4997                     // If match failed we must backtrack, so
4998                     // the loop count should NOT be incremented
4999                     if (!result)
5000                         matcher.locals[countIndex] = count;
5001                     return result;
5002                 }
5003                 return false;
5004             }
5005             return next.match(matcher, i, seq);
5006         }
5007         boolean matchInit(Matcher matcher, int i, CharSequence seq) {
5008             int save = matcher.locals[countIndex];
5009             boolean ret = false;
5010             if (0 < cmin) {
5011                 matcher.locals[countIndex] = 1;
5012                 ret = body.match(matcher, i, seq);
5013             } else if (next.match(matcher, i, seq)) {
5014                 ret = true;
5015             } else if (0 < cmax) {
5016                 matcher.locals[countIndex] = 1;
5017                 ret = body.match(matcher, i, seq);
5018             }
5019             matcher.locals[countIndex] = save;
5020             return ret;
5021         }
5022         boolean study(TreeInfo info) {
5023             info.maxValid = false;
5024             info.deterministic = false;
5025             return false;
5026         }
5027     }
5028 
5029     /**
5030      * Refers to a group in the regular expression. Attempts to match
5031      * whatever the group referred to last matched.
5032      */
5033     static class BackRef extends Node {
5034         int groupIndex;
5035         BackRef(int groupCount) {
5036             super();
5037             groupIndex = groupCount + groupCount;
5038         }
5039         boolean match(Matcher matcher, int i, CharSequence seq) {
5040             int j = matcher.groups[groupIndex];
5041             int k = matcher.groups[groupIndex+1];
5042 
5043             int groupSize = k - j;
5044             // If the referenced group didn't match, neither can this
5045             if (j < 0)
5046                 return false;
5047 
5048             // If there isn't enough input left no match
5049             if (i + groupSize > matcher.to) {
5050                 matcher.hitEnd = true;
5051                 return false;
5052             }
5053             // Check each new char to make sure it matches what the group
5054             // referenced matched last time around
5055             for (int index=0; index<groupSize; index++)
5056                 if (seq.charAt(i+index) != seq.charAt(j+index))
5057                     return false;
5058 
5059             return next.match(matcher, i+groupSize, seq);
5060         }
5061         boolean study(TreeInfo info) {
5062             info.maxValid = false;
5063             return next.study(info);
5064         }
5065     }
5066 
5067     static class CIBackRef extends Node {
5068         int groupIndex;
5069         boolean doUnicodeCase;
5070         CIBackRef(int groupCount, boolean doUnicodeCase) {
5071             super();
5072             groupIndex = groupCount + groupCount;
5073             this.doUnicodeCase = doUnicodeCase;
5074         }
5075         boolean match(Matcher matcher, int i, CharSequence seq) {
5076             int j = matcher.groups[groupIndex];
5077             int k = matcher.groups[groupIndex+1];
5078 
5079             int groupSize = k - j;
5080 
5081             // If the referenced group didn't match, neither can this
5082             if (j < 0)
5083                 return false;
5084 
5085             // If there isn't enough input left no match
5086             if (i + groupSize > matcher.to) {
5087                 matcher.hitEnd = true;
5088                 return false;
5089             }
5090 
5091             // Check each new char to make sure it matches what the group
5092             // referenced matched last time around
5093             int x = i;
5094             for (int index=0; index<groupSize; index++) {
5095                 int c1 = Character.codePointAt(seq, x);
5096                 int c2 = Character.codePointAt(seq, j);
5097                 if (c1 != c2) {
5098                     if (doUnicodeCase) {
5099                         int cc1 = Character.toUpperCase(c1);
5100                         int cc2 = Character.toUpperCase(c2);
5101                         if (cc1 != cc2 &&
5102                             Character.toLowerCase(cc1) !=
5103                             Character.toLowerCase(cc2))
5104                             return false;
5105                     } else {
5106                         if (ASCII.toLower(c1) != ASCII.toLower(c2))
5107                             return false;
5108                     }
5109                 }
5110                 x += Character.charCount(c1);
5111                 j += Character.charCount(c2);
5112             }
5113 
5114             return next.match(matcher, i+groupSize, seq);
5115         }
5116         boolean study(TreeInfo info) {
5117             info.maxValid = false;
5118             return next.study(info);
5119         }
5120     }
5121 
5122     /**
5123      * Searches until the next instance of its atom. This is useful for
5124      * finding the atom efficiently without passing an instance of it
5125      * (greedy problem) and without a lot of wasted search time (reluctant
5126      * problem).
5127      */
5128     static final class First extends Node {
5129         Node atom;
5130         First(Node node) {
5131             this.atom = BnM.optimize(node);
5132         }
5133         boolean match(Matcher matcher, int i, CharSequence seq) {
5134             if (atom instanceof BnM) {
5135                 return atom.match(matcher, i, seq)
5136                     && next.match(matcher, matcher.last, seq);
5137             }
5138             for (;;) {
5139                 if (i > matcher.to) {
5140                     matcher.hitEnd = true;
5141                     return false;
5142                 }
5143                 if (atom.match(matcher, i, seq)) {
5144                     return next.match(matcher, matcher.last, seq);
5145                 }
5146                 i += countChars(seq, i, 1);
5147                 matcher.first++;
5148             }
5149         }
5150         boolean study(TreeInfo info) {
5151             atom.study(info);
5152             info.maxValid = false;
5153             info.deterministic = false;
5154             return next.study(info);
5155         }
5156     }
5157 
5158     static final class Conditional extends Node {
5159         Node cond, yes, not;
5160         Conditional(Node cond, Node yes, Node not) {
5161             this.cond = cond;
5162             this.yes = yes;
5163             this.not = not;
5164         }
5165         boolean match(Matcher matcher, int i, CharSequence seq) {
5166             if (cond.match(matcher, i, seq)) {
5167                 return yes.match(matcher, i, seq);
5168             } else {
5169                 return not.match(matcher, i, seq);
5170             }
5171         }
5172         boolean study(TreeInfo info) {
5173             int minL = info.minLength;
5174             int maxL = info.maxLength;
5175             boolean maxV = info.maxValid;
5176             info.reset();
5177             yes.study(info);
5178 
5179             int minL2 = info.minLength;
5180             int maxL2 = info.maxLength;
5181             boolean maxV2 = info.maxValid;
5182             info.reset();
5183             not.study(info);
5184 
5185             info.minLength = minL + Math.min(minL2, info.minLength);
5186             info.maxLength = maxL + Math.max(maxL2, info.maxLength);
5187             info.maxValid = (maxV & maxV2 & info.maxValid);
5188             info.deterministic = false;
5189             return next.study(info);
5190         }
5191     }
5192 
5193     /**
5194      * Zero width positive lookahead.
5195      */
5196     static final class Pos extends Node {
5197         Node cond;
5198         Pos(Node cond) {
5199             this.cond = cond;
5200         }
5201         boolean match(Matcher matcher, int i, CharSequence seq) {
5202             int savedTo = matcher.to;
5203             boolean conditionMatched = false;
5204 
5205             // Relax transparent region boundaries for lookahead
5206             if (matcher.transparentBounds)
5207                 matcher.to = matcher.getTextLength();
5208             try {
5209                 conditionMatched = cond.match(matcher, i, seq);
5210             } finally {
5211                 // Reinstate region boundaries
5212                 matcher.to = savedTo;
5213             }
5214             return conditionMatched && next.match(matcher, i, seq);
5215         }
5216     }
5217 
5218     /**
5219      * Zero width negative lookahead.
5220      */
5221     static final class Neg extends Node {
5222         Node cond;
5223         Neg(Node cond) {
5224             this.cond = cond;
5225         }
5226         boolean match(Matcher matcher, int i, CharSequence seq) {
5227             int savedTo = matcher.to;
5228             boolean conditionMatched = false;
5229 
5230             // Relax transparent region boundaries for lookahead
5231             if (matcher.transparentBounds)
5232                 matcher.to = matcher.getTextLength();
5233             try {
5234                 if (i < matcher.to) {
5235                     conditionMatched = !cond.match(matcher, i, seq);
5236                 } else {
5237                     // If a negative lookahead succeeds then more input
5238                     // could cause it to fail!
5239                     matcher.requireEnd = true;
5240                     conditionMatched = !cond.match(matcher, i, seq);
5241                 }
5242             } finally {
5243                 // Reinstate region boundaries
5244                 matcher.to = savedTo;
5245             }
5246             return conditionMatched && next.match(matcher, i, seq);
5247         }
5248     }
5249 
5250     /**
5251      * For use with lookbehinds; matches the position where the lookbehind
5252      * was encountered.
5253      */
5254     static Node lookbehindEnd = new Node() {
5255         boolean match(Matcher matcher, int i, CharSequence seq) {
5256             return i == matcher.lookbehindTo;
5257         }
5258     };
5259 
5260     /**
5261      * Zero width positive lookbehind.
5262      */
5263     static class Behind extends Node {
5264         Node cond;
5265         int rmax, rmin;
5266         Behind(Node cond, int rmax, int rmin) {
5267             this.cond = cond;
5268             this.rmax = rmax;
5269             this.rmin = rmin;
5270         }
5271 
5272         boolean match(Matcher matcher, int i, CharSequence seq) {
5273             int savedFrom = matcher.from;
5274             boolean conditionMatched = false;
5275             int startIndex = (!matcher.transparentBounds) ?
5276                              matcher.from : 0;
5277             int from = Math.max(i - rmax, startIndex);
5278             // Set end boundary
5279             int savedLBT = matcher.lookbehindTo;
5280             matcher.lookbehindTo = i;
5281             // Relax transparent region boundaries for lookbehind
5282             if (matcher.transparentBounds)
5283                 matcher.from = 0;
5284             for (int j = i - rmin; !conditionMatched && j >= from; j--) {
5285                 conditionMatched = cond.match(matcher, j, seq);
5286             }
5287             matcher.from = savedFrom;
5288             matcher.lookbehindTo = savedLBT;
5289             return conditionMatched && next.match(matcher, i, seq);
5290         }
5291     }
5292 
5293     /**
5294      * Zero width positive lookbehind, including supplementary
5295      * characters or unpaired surrogates.
5296      */
5297     static final class BehindS extends Behind {
5298         BehindS(Node cond, int rmax, int rmin) {
5299             super(cond, rmax, rmin);
5300         }
5301         boolean match(Matcher matcher, int i, CharSequence seq) {
5302             int rmaxChars = countChars(seq, i, -rmax);
5303             int rminChars = countChars(seq, i, -rmin);
5304             int savedFrom = matcher.from;
5305             int startIndex = (!matcher.transparentBounds) ?
5306                              matcher.from : 0;
5307             boolean conditionMatched = false;
5308             int from = Math.max(i - rmaxChars, startIndex);
5309             // Set end boundary
5310             int savedLBT = matcher.lookbehindTo;
5311             matcher.lookbehindTo = i;
5312             // Relax transparent region boundaries for lookbehind
5313             if (matcher.transparentBounds)
5314                 matcher.from = 0;
5315 
5316             for (int j = i - rminChars;
5317                  !conditionMatched && j >= from;
5318                  j -= j>from ? countChars(seq, j, -1) : 1) {
5319                 conditionMatched = cond.match(matcher, j, seq);
5320             }
5321             matcher.from = savedFrom;
5322             matcher.lookbehindTo = savedLBT;
5323             return conditionMatched && next.match(matcher, i, seq);
5324         }
5325     }
5326 
5327     /**
5328      * Zero width negative lookbehind.
5329      */
5330     static class NotBehind extends Node {
5331         Node cond;
5332         int rmax, rmin;
5333         NotBehind(Node cond, int rmax, int rmin) {
5334             this.cond = cond;
5335             this.rmax = rmax;
5336             this.rmin = rmin;
5337         }
5338 
5339         boolean match(Matcher matcher, int i, CharSequence seq) {
5340             int savedLBT = matcher.lookbehindTo;
5341             int savedFrom = matcher.from;
5342             boolean conditionMatched = false;
5343             int startIndex = (!matcher.transparentBounds) ?
5344                              matcher.from : 0;
5345             int from = Math.max(i - rmax, startIndex);
5346             matcher.lookbehindTo = i;
5347             // Relax transparent region boundaries for lookbehind
5348             if (matcher.transparentBounds)
5349                 matcher.from = 0;
5350             for (int j = i - rmin; !conditionMatched && j >= from; j--) {
5351                 conditionMatched = cond.match(matcher, j, seq);
5352             }
5353             // Reinstate region boundaries
5354             matcher.from = savedFrom;
5355             matcher.lookbehindTo = savedLBT;
5356             return !conditionMatched && next.match(matcher, i, seq);
5357         }
5358     }
5359 
5360     /**
5361      * Zero width negative lookbehind, including supplementary
5362      * characters or unpaired surrogates.
5363      */
5364     static final class NotBehindS extends NotBehind {
5365         NotBehindS(Node cond, int rmax, int rmin) {
5366             super(cond, rmax, rmin);
5367         }
5368         boolean match(Matcher matcher, int i, CharSequence seq) {
5369             int rmaxChars = countChars(seq, i, -rmax);
5370             int rminChars = countChars(seq, i, -rmin);
5371             int savedFrom = matcher.from;
5372             int savedLBT = matcher.lookbehindTo;
5373             boolean conditionMatched = false;
5374             int startIndex = (!matcher.transparentBounds) ?
5375                              matcher.from : 0;
5376             int from = Math.max(i - rmaxChars, startIndex);
5377             matcher.lookbehindTo = i;
5378             // Relax transparent region boundaries for lookbehind
5379             if (matcher.transparentBounds)
5380                 matcher.from = 0;
5381             for (int j = i - rminChars;
5382                  !conditionMatched && j >= from;
5383                  j -= j>from ? countChars(seq, j, -1) : 1) {
5384                 conditionMatched = cond.match(matcher, j, seq);
5385             }
5386             //Reinstate region boundaries
5387             matcher.from = savedFrom;
5388             matcher.lookbehindTo = savedLBT;
5389             return !conditionMatched && next.match(matcher, i, seq);
5390         }
5391     }
5392 
5393     /**
5394      * Handles word boundaries. Includes a field to allow this one class to
5395      * deal with the different types of word boundaries we can match. The word
5396      * characters include underscores, letters, and digits. Non spacing marks
5397      * can are also part of a word if they have a base character, otherwise
5398      * they are ignored for purposes of finding word boundaries.
5399      */
5400     static final class Bound extends Node {
5401         static int LEFT = 0x1;
5402         static int RIGHT= 0x2;
5403         static int BOTH = 0x3;
5404         static int NONE = 0x4;
5405         int type;
5406         boolean useUWORD;
5407         Bound(int n, boolean useUWORD) {
5408             type = n;
5409             this.useUWORD = useUWORD;
5410         }
5411 
5412         boolean isWord(int ch) {
5413             return useUWORD ? CharPredicates.WORD().is(ch)
5414                             : (ch == '_' || Character.isLetterOrDigit(ch));
5415         }
5416 
5417         int check(Matcher matcher, int i, CharSequence seq) {
5418             int ch;
5419             boolean left = false;
5420             int startIndex = matcher.from;
5421             int endIndex = matcher.to;
5422             if (matcher.transparentBounds) {
5423                 startIndex = 0;
5424                 endIndex = matcher.getTextLength();
5425             }
5426             if (i > startIndex) {
5427                 ch = Character.codePointBefore(seq, i);
5428                 left = (isWord(ch) ||
5429                     ((Character.getType(ch) == Character.NON_SPACING_MARK)
5430                      && hasBaseCharacter(matcher, i-1, seq)));
5431             }
5432             boolean right = false;
5433             if (i < endIndex) {
5434                 ch = Character.codePointAt(seq, i);
5435                 right = (isWord(ch) ||
5436                     ((Character.getType(ch) == Character.NON_SPACING_MARK)
5437                      && hasBaseCharacter(matcher, i, seq)));
5438             } else {
5439                 // Tried to access char past the end
5440                 matcher.hitEnd = true;
5441                 // The addition of another char could wreck a boundary
5442                 matcher.requireEnd = true;
5443             }
5444             return ((left ^ right) ? (right ? LEFT : RIGHT) : NONE);
5445         }
5446         boolean match(Matcher matcher, int i, CharSequence seq) {
5447             return (check(matcher, i, seq) & type) > 0
5448                 && next.match(matcher, i, seq);
5449         }
5450     }
5451 
5452     /**
5453      * Non spacing marks only count as word characters in bounds calculations
5454      * if they have a base character.
5455      */
5456     private static boolean hasBaseCharacter(Matcher matcher, int i,
5457                                             CharSequence seq)
5458     {
5459         int start = (!matcher.transparentBounds) ?
5460             matcher.from : 0;
5461         for (int x=i; x >= start; x--) {
5462             int ch = Character.codePointAt(seq, x);
5463             if (Character.isLetterOrDigit(ch))
5464                 return true;
5465             if (Character.getType(ch) == Character.NON_SPACING_MARK)
5466                 continue;
5467             return false;
5468         }
5469         return false;
5470     }
5471 
5472     /**
5473      * Attempts to match a slice in the input using the Boyer-Moore string
5474      * matching algorithm. The algorithm is based on the idea that the
5475      * pattern can be shifted farther ahead in the search text if it is
5476      * matched right to left.
5477      * <p>
5478      * The pattern is compared to the input one character at a time, from
5479      * the rightmost character in the pattern to the left. If the characters
5480      * all match the pattern has been found. If a character does not match,
5481      * the pattern is shifted right a distance that is the maximum of two
5482      * functions, the bad character shift and the good suffix shift. This
5483      * shift moves the attempted match position through the input more
5484      * quickly than a naive one position at a time check.
5485      * <p>
5486      * The bad character shift is based on the character from the text that
5487      * did not match. If the character does not appear in the pattern, the
5488      * pattern can be shifted completely beyond the bad character. If the
5489      * character does occur in the pattern, the pattern can be shifted to
5490      * line the pattern up with the next occurrence of that character.
5491      * <p>
5492      * The good suffix shift is based on the idea that some subset on the right
5493      * side of the pattern has matched. When a bad character is found, the
5494      * pattern can be shifted right by the pattern length if the subset does
5495      * not occur again in pattern, or by the amount of distance to the
5496      * next occurrence of the subset in the pattern.
5497      *
5498      * Boyer-Moore search methods adapted from code by Amy Yu.
5499      */
5500     static class BnM extends Node {
5501         int[] buffer;
5502         int[] lastOcc;
5503         int[] optoSft;
5504 
5505         /**
5506          * Pre calculates arrays needed to generate the bad character
5507          * shift and the good suffix shift. Only the last seven bits
5508          * are used to see if chars match; This keeps the tables small
5509          * and covers the heavily used ASCII range, but occasionally
5510          * results in an aliased match for the bad character shift.
5511          */
5512         static Node optimize(Node node) {
5513             if (!(node instanceof Slice)) {
5514                 return node;
5515             }
5516 
5517             int[] src = ((Slice) node).buffer;
5518             int patternLength = src.length;
5519             // The BM algorithm requires a bit of overhead;
5520             // If the pattern is short don't use it, since
5521             // a shift larger than the pattern length cannot
5522             // be used anyway.
5523             if (patternLength < 4) {
5524                 return node;
5525             }
5526             int i, j, k;
5527             int[] lastOcc = new int[128];
5528             int[] optoSft = new int[patternLength];
5529             // Precalculate part of the bad character shift
5530             // It is a table for where in the pattern each
5531             // lower 7-bit value occurs
5532             for (i = 0; i < patternLength; i++) {
5533                 lastOcc[src[i]&0x7F] = i + 1;
5534             }
5535             // Precalculate the good suffix shift
5536             // i is the shift amount being considered
5537 NEXT:       for (i = patternLength; i > 0; i--) {
5538                 // j is the beginning index of suffix being considered
5539                 for (j = patternLength - 1; j >= i; j--) {
5540                     // Testing for good suffix
5541                     if (src[j] == src[j-i]) {
5542                         // src[j..len] is a good suffix
5543                         optoSft[j-1] = i;
5544                     } else {
5545                         // No match. The array has already been
5546                         // filled up with correct values before.
5547                         continue NEXT;
5548                     }
5549                 }
5550                 // This fills up the remaining of optoSft
5551                 // any suffix can not have larger shift amount
5552                 // then its sub-suffix. Why???
5553                 while (j > 0) {
5554                     optoSft[--j] = i;
5555                 }
5556             }
5557             // Set the guard value because of unicode compression
5558             optoSft[patternLength-1] = 1;
5559             if (node instanceof SliceS)
5560                 return new BnMS(src, lastOcc, optoSft, node.next);
5561             return new BnM(src, lastOcc, optoSft, node.next);
5562         }
5563         BnM(int[] src, int[] lastOcc, int[] optoSft, Node next) {
5564             this.buffer = src;
5565             this.lastOcc = lastOcc;
5566             this.optoSft = optoSft;
5567             this.next = next;
5568         }
5569         boolean match(Matcher matcher, int i, CharSequence seq) {
5570             int[] src = buffer;
5571             int patternLength = src.length;
5572             int last = matcher.to - patternLength;
5573 
5574             // Loop over all possible match positions in text
5575 NEXT:       while (i <= last) {
5576                 // Loop over pattern from right to left
5577                 for (int j = patternLength - 1; j >= 0; j--) {
5578                     int ch = seq.charAt(i+j);
5579                     if (ch != src[j]) {
5580                         // Shift search to the right by the maximum of the
5581                         // bad character shift and the good suffix shift
5582                         i += Math.max(j + 1 - lastOcc[ch&0x7F], optoSft[j]);
5583                         continue NEXT;
5584                     }
5585                 }
5586                 // Entire pattern matched starting at i
5587                 matcher.first = i;
5588                 boolean ret = next.match(matcher, i + patternLength, seq);
5589                 if (ret) {
5590                     matcher.first = i;
5591                     matcher.groups[0] = matcher.first;
5592                     matcher.groups[1] = matcher.last;
5593                     return true;
5594                 }
5595                 i++;
5596             }
5597             // BnM is only used as the leading node in the unanchored case,
5598             // and it replaced its Start() which always searches to the end
5599             // if it doesn't find what it's looking for, so hitEnd is true.
5600             matcher.hitEnd = true;
5601             return false;
5602         }
5603         boolean study(TreeInfo info) {
5604             info.minLength += buffer.length;
5605             info.maxValid = false;
5606             return next.study(info);
5607         }
5608     }
5609 
5610     /**
5611      * Supplementary support version of BnM(). Unpaired surrogates are
5612      * also handled by this class.
5613      */
5614     static final class BnMS extends BnM {
5615         int lengthInChars;
5616 
5617         BnMS(int[] src, int[] lastOcc, int[] optoSft, Node next) {
5618             super(src, lastOcc, optoSft, next);
5619             for (int cp : buffer) {
5620                 lengthInChars += Character.charCount(cp);
5621             }
5622         }
5623         boolean match(Matcher matcher, int i, CharSequence seq) {
5624             int[] src = buffer;
5625             int patternLength = src.length;
5626             int last = matcher.to - lengthInChars;
5627 
5628             // Loop over all possible match positions in text
5629 NEXT:       while (i <= last) {
5630                 // Loop over pattern from right to left
5631                 int ch;
5632                 for (int j = countChars(seq, i, patternLength), x = patternLength - 1;
5633                      j > 0; j -= Character.charCount(ch), x--) {
5634                     ch = Character.codePointBefore(seq, i+j);
5635                     if (ch != src[x]) {
5636                         // Shift search to the right by the maximum of the
5637                         // bad character shift and the good suffix shift
5638                         int n = Math.max(x + 1 - lastOcc[ch&0x7F], optoSft[x]);
5639                         i += countChars(seq, i, n);
5640                         continue NEXT;
5641                     }
5642                 }
5643                 // Entire pattern matched starting at i
5644                 matcher.first = i;
5645                 boolean ret = next.match(matcher, i + lengthInChars, seq);
5646                 if (ret) {
5647                     matcher.first = i;
5648                     matcher.groups[0] = matcher.first;
5649                     matcher.groups[1] = matcher.last;
5650                     return true;
5651                 }
5652                 i += countChars(seq, i, 1);
5653             }
5654             matcher.hitEnd = true;
5655             return false;
5656         }
5657     }
5658 
5659     @FunctionalInterface
5660     static interface CharPredicate {
5661         boolean is(int ch);
5662 
5663         default CharPredicate and(CharPredicate p) {
5664             return ch -> is(ch) && p.is(ch);
5665         }
5666         default CharPredicate union(CharPredicate p) {
5667             return ch -> is(ch) || p.is(ch);
5668         }
5669         default CharPredicate union(CharPredicate p1,
5670                                     CharPredicate p2 ) {
5671             return ch -> is(ch) || p1.is(ch) || p2.is(ch);
5672         }
5673         default CharPredicate negate() {
5674             return ch -> !is(ch);
5675         }
5676     }
5677 
5678     static interface BmpCharPredicate extends CharPredicate {
5679 
5680         default CharPredicate and(CharPredicate p) {
5681             if(p instanceof BmpCharPredicate)
5682                 return (BmpCharPredicate)(ch -> is(ch) && p.is(ch));
5683             return ch -> is(ch) && p.is(ch);
5684         }
5685         default CharPredicate union(CharPredicate p) {
5686             if (p instanceof BmpCharPredicate)
5687                 return (BmpCharPredicate)(ch -> is(ch) || p.is(ch));
5688             return ch -> is(ch) || p.is(ch);
5689         }
5690         static CharPredicate union(CharPredicate... predicates) {
5691             CharPredicate cp = ch -> {
5692                 for (CharPredicate p : predicates) {
5693                     if (!p.is(ch))
5694                         return false;
5695                 }
5696                 return true;
5697             };
5698             for (CharPredicate p : predicates) {
5699                 if (! (p instanceof BmpCharPredicate))
5700                     return cp;
5701             }
5702             return (BmpCharPredicate)cp;
5703         }
5704     }
5705 
5706     /**
5707      * matches a Perl vertical whitespace
5708      */
5709     static BmpCharPredicate VertWS() {
5710         return cp -> (cp >= 0x0A && cp <= 0x0D) ||
5711             cp == 0x85 || cp == 0x2028 || cp == 0x2029;
5712     }
5713 
5714     /**
5715      * matches a Perl horizontal whitespace
5716      */
5717     static BmpCharPredicate HorizWS() {
5718         return cp ->
5719             cp == 0x09 || cp == 0x20 || cp == 0xa0 || cp == 0x1680 ||
5720             cp == 0x180e || cp >= 0x2000 && cp <= 0x200a ||  cp == 0x202f ||
5721             cp == 0x205f || cp == 0x3000;
5722     }
5723 
5724     /**
5725      *  for the Unicode category ALL and the dot metacharacter when
5726      *  in dotall mode.
5727      */
5728     static CharPredicate ALL() {
5729         return ch -> true;
5730     }
5731 
5732     /**
5733      * for the dot metacharacter when dotall is not enabled.
5734      */
5735     static CharPredicate DOT() {
5736         return ch ->
5737             (ch != '\n' && ch != '\r'
5738             && (ch|1) != '\u2029'
5739             && ch != '\u0085');
5740     }
5741 
5742     /**
5743      *  the dot metacharacter when dotall is not enabled but UNIX_LINES is enabled.
5744      */
5745     static CharPredicate UNIXDOT() {
5746         return ch ->  ch != '\n';
5747     }
5748 
5749     /**
5750      * Indicate that matches a Supplementary Unicode character
5751      */
5752     static CharPredicate SingleS(int c) {
5753         return ch -> ch == c;
5754     }
5755 
5756     /**
5757      * A bmp/optimized predicate of single
5758      */
5759     static BmpCharPredicate Single(int c) {
5760         return ch -> ch == c;
5761     }
5762 
5763     /**
5764      * Case insensitive matches a given BMP character
5765      */
5766     static BmpCharPredicate SingleI(int lower, int upper) {
5767         return ch -> ch == lower || ch == upper;
5768     }
5769 
5770     /**
5771      * Unicode case insensitive matches a given Unicode character
5772      */
5773     static CharPredicate SingleU(int lower) {
5774         return ch -> lower == ch ||
5775                      lower == Character.toLowerCase(Character.toUpperCase(ch));
5776     }
5777 
5778     private static boolean inRange(int lower, int ch, int upper) {
5779         return lower <= ch && ch <= upper;
5780     }
5781 
5782     /**
5783      * Charactrs within a explicit value range
5784      */
5785     static CharPredicate Range(int lower, int upper) {
5786         if (upper < Character.MIN_HIGH_SURROGATE ||
5787             lower > Character.MAX_HIGH_SURROGATE &&
5788             upper < Character.MIN_SUPPLEMENTARY_CODE_POINT)
5789             return (BmpCharPredicate)(ch -> inRange(lower, ch, upper));
5790         return ch -> inRange(lower, ch, upper);
5791     }
5792 
5793    /**
5794     * Charactrs within a explicit value range in a case insensitive manner.
5795     */
5796     static CharPredicate CIRange(int lower, int upper) {
5797         return ch -> inRange(lower, ch, upper) ||
5798                      ASCII.isAscii(ch) &&
5799                      (inRange(lower, ASCII.toUpper(ch), upper) ||
5800                       inRange(lower, ASCII.toLower(ch), upper));
5801     }
5802 
5803     static CharPredicate CIRangeU(int lower, int upper) {
5804         return ch -> {
5805             if (inRange(lower, ch, upper))
5806                 return true;
5807             int up = Character.toUpperCase(ch);
5808             return inRange(lower, up, upper) ||
5809                    inRange(lower, Character.toLowerCase(up), upper);
5810         };
5811     }
5812 
5813     /**
5814      *  This must be the very first initializer.
5815      */
5816     static final Node accept = new Node();
5817 
5818     static final Node lastAccept = new LastNode();
5819 
5820     /**
5821      * Creates a predicate that tests if this pattern is found in a given input
5822      * string.
5823      *
5824      * @apiNote
5825      * This method creates a predicate that behaves as if it creates a matcher
5826      * from the input sequence and then calls {@code find}, for example a
5827      * predicate of the form:
5828      * <pre>{@code
5829      *   s -> matcher(s).find();
5830      * }</pre>
5831      *
5832      * @return  The predicate which can be used for finding a match on a
5833      *          subsequence of a string
5834      * @since   1.8
5835      * @see     Matcher#find
5836      */
5837     public Predicate<String> asPredicate() {
5838         return s -> matcher(s).find();
5839     }
5840 
5841     /**
5842      * Creates a predicate that tests if this pattern matches a given input string.
5843      *
5844      * @apiNote
5845      * This method creates a predicate that behaves as if it creates a matcher
5846      * from the input sequence and then calls {@code matches}, for example a
5847      * predicate of the form:
5848      * <pre>{@code
5849      *   s -> matcher(s).matches();
5850      * }</pre>
5851      *
5852      * @return  The predicate which can be used for matching an input string
5853      *          against this pattern.
5854      * @since   11
5855      * @see     Matcher#matches
5856      */
5857     public Predicate<String> asMatchPredicate() {
5858         return s -> matcher(s).matches();
5859     }
5860 
5861     /**
5862      * Creates a stream from the given input sequence around matches of this
5863      * pattern.
5864      *
5865      * <p> The stream returned by this method contains each substring of the
5866      * input sequence that is terminated by another subsequence that matches
5867      * this pattern or is terminated by the end of the input sequence.  The
5868      * substrings in the stream are in the order in which they occur in the
5869      * input. Trailing empty strings will be discarded and not encountered in
5870      * the stream.
5871      *
5872      * <p> If this pattern does not match any subsequence of the input then
5873      * the resulting stream has just one element, namely the input sequence in
5874      * string form.
5875      *
5876      * <p> When there is a positive-width match at the beginning of the input
5877      * sequence then an empty leading substring is included at the beginning
5878      * of the stream. A zero-width match at the beginning however never produces
5879      * such empty leading substring.
5880      *
5881      * <p> If the input sequence is mutable, it must remain constant during the
5882      * execution of the terminal stream operation.  Otherwise, the result of the
5883      * terminal stream operation is undefined.
5884      *
5885      * @param   input
5886      *          The character sequence to be split
5887      *
5888      * @return  The stream of strings computed by splitting the input
5889      *          around matches of this pattern
5890      * @see     #split(CharSequence)
5891      * @since   1.8
5892      */
5893     public Stream<String> splitAsStream(final CharSequence input) {
5894         class MatcherIterator implements Iterator<String> {
5895             private Matcher matcher;
5896             // The start position of the next sub-sequence of input
5897             // when current == input.length there are no more elements
5898             private int current;
5899             // null if the next element, if any, needs to obtained
5900             private String nextElement;
5901             // > 0 if there are N next empty elements
5902             private int emptyElementCount;
5903 
5904             public String next() {
5905                 if (!hasNext())
5906                     throw new NoSuchElementException();
5907 
5908                 if (emptyElementCount == 0) {
5909                     String n = nextElement;
5910                     nextElement = null;
5911                     return n;
5912                 } else {
5913                     emptyElementCount--;
5914                     return "";
5915                 }
5916             }
5917 
5918             public boolean hasNext() {
5919                 if (matcher == null) {
5920                     matcher = matcher(input);
5921                     // If the input is an empty string then the result can only be a
5922                     // stream of the input.  Induce that by setting the empty
5923                     // element count to 1
5924                     emptyElementCount = input.length() == 0 ? 1 : 0;
5925                 }
5926                 if (nextElement != null || emptyElementCount > 0)
5927                     return true;
5928 
5929                 if (current == input.length())
5930                     return false;
5931 
5932                 // Consume the next matching element
5933                 // Count sequence of matching empty elements
5934                 while (matcher.find()) {
5935                     nextElement = input.subSequence(current, matcher.start()).toString();
5936                     current = matcher.end();
5937                     if (!nextElement.isEmpty()) {
5938                         return true;
5939                     } else if (current > 0) { // no empty leading substring for zero-width
5940                                               // match at the beginning of the input
5941                         emptyElementCount++;
5942                     }
5943                 }
5944 
5945                 // Consume last matching element
5946                 nextElement = input.subSequence(current, input.length()).toString();
5947                 current = input.length();
5948                 if (!nextElement.isEmpty()) {
5949                     return true;
5950                 } else {
5951                     // Ignore a terminal sequence of matching empty elements
5952                     emptyElementCount = 0;
5953                     nextElement = null;
5954                     return false;
5955                 }
5956             }
5957         }
5958         return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
5959                 new MatcherIterator(), Spliterator.ORDERED | Spliterator.NONNULL), false);
5960     }
5961 }