rev 12318 : [mq]: 8131034-Cleanup-in-j.u.regex.Pattern.quote

   1 /*
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   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
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   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
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  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
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  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
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  25 
  26 package java.util.regex;
  27 
  28 import java.text.Normalizer;
  29 import java.util.Locale;
  30 import java.util.Iterator;
  31 import java.util.Map;
  32 import java.util.ArrayList;
  33 import java.util.HashMap;
  34 import java.util.Arrays;
  35 import java.util.NoSuchElementException;
  36 import java.util.Spliterator;
  37 import java.util.Spliterators;
  38 import java.util.function.Predicate;
  39 import java.util.stream.Stream;
  40 import java.util.stream.StreamSupport;
  41 
  42 
  43 /**
  44  * A compiled representation of a regular expression.
  45  *
  46  * <p> A regular expression, specified as a string, must first be compiled into
  47  * an instance of this class.  The resulting pattern can then be used to create
  48  * a {@link Matcher} object that can match arbitrary {@linkplain
  49  * java.lang.CharSequence character sequences} against the regular
  50  * expression.  All of the state involved in performing a match resides in the
  51  * matcher, so many matchers can share the same pattern.
  52  *
  53  * <p> A typical invocation sequence is thus
  54  *
  55  * <blockquote><pre>
  56  * Pattern p = Pattern.{@link #compile compile}("a*b");
  57  * Matcher m = p.{@link #matcher matcher}("aaaaab");
  58  * boolean b = m.{@link Matcher#matches matches}();</pre></blockquote>
  59  *
  60  * <p> A {@link #matches matches} method is defined by this class as a
  61  * convenience for when a regular expression is used just once.  This method
  62  * compiles an expression and matches an input sequence against it in a single
  63  * invocation.  The statement
  64  *
  65  * <blockquote><pre>
  66  * boolean b = Pattern.matches("a*b", "aaaaab");</pre></blockquote>
  67  *
  68  * is equivalent to the three statements above, though for repeated matches it
  69  * is less efficient since it does not allow the compiled pattern to be reused.
  70  *
  71  * <p> Instances of this class are immutable and are safe for use by multiple
  72  * concurrent threads.  Instances of the {@link Matcher} class are not safe for
  73  * such use.
  74  *
  75  *
  76  * <h3><a name="sum">Summary of regular-expression constructs</a></h3>
  77  *
  78  * <table border="0" cellpadding="1" cellspacing="0"
  79  *  summary="Regular expression constructs, and what they match">
  80  *
  81  * <tr align="left">
  82  * <th align="left" id="construct">Construct</th>
  83  * <th align="left" id="matches">Matches</th>
  84  * </tr>
  85  *
  86  * <tr><th>&nbsp;</th></tr>
  87  * <tr align="left"><th colspan="2" id="characters">Characters</th></tr>
  88  *
  89  * <tr><td valign="top" headers="construct characters"><i>x</i></td>
  90  *     <td headers="matches">The character <i>x</i></td></tr>
  91  * <tr><td valign="top" headers="construct characters"><tt>\\</tt></td>
  92  *     <td headers="matches">The backslash character</td></tr>
  93  * <tr><td valign="top" headers="construct characters"><tt>\0</tt><i>n</i></td>
  94  *     <td headers="matches">The character with octal value <tt>0</tt><i>n</i>
  95  *         (0&nbsp;<tt>&lt;=</tt>&nbsp;<i>n</i>&nbsp;<tt>&lt;=</tt>&nbsp;7)</td></tr>
  96  * <tr><td valign="top" headers="construct characters"><tt>\0</tt><i>nn</i></td>
  97  *     <td headers="matches">The character with octal value <tt>0</tt><i>nn</i>
  98  *         (0&nbsp;<tt>&lt;=</tt>&nbsp;<i>n</i>&nbsp;<tt>&lt;=</tt>&nbsp;7)</td></tr>
  99  * <tr><td valign="top" headers="construct characters"><tt>\0</tt><i>mnn</i></td>
 100  *     <td headers="matches">The character with octal value <tt>0</tt><i>mnn</i>
 101  *         (0&nbsp;<tt>&lt;=</tt>&nbsp;<i>m</i>&nbsp;<tt>&lt;=</tt>&nbsp;3,
 102  *         0&nbsp;<tt>&lt;=</tt>&nbsp;<i>n</i>&nbsp;<tt>&lt;=</tt>&nbsp;7)</td></tr>
 103  * <tr><td valign="top" headers="construct characters"><tt>\x</tt><i>hh</i></td>
 104  *     <td headers="matches">The character with hexadecimal&nbsp;value&nbsp;<tt>0x</tt><i>hh</i></td></tr>
 105  * <tr><td valign="top" headers="construct characters"><tt>\u</tt><i>hhhh</i></td>
 106  *     <td headers="matches">The character with hexadecimal&nbsp;value&nbsp;<tt>0x</tt><i>hhhh</i></td></tr>
 107  * <tr><td valign="top" headers="construct characters"><tt>\x</tt><i>{h...h}</i></td>
 108  *     <td headers="matches">The character with hexadecimal&nbsp;value&nbsp;<tt>0x</tt><i>h...h</i>
 109  *         ({@link java.lang.Character#MIN_CODE_POINT Character.MIN_CODE_POINT}
 110  *         &nbsp;&lt;=&nbsp;<tt>0x</tt><i>h...h</i>&nbsp;&lt;=&nbsp;
 111  *          {@link java.lang.Character#MAX_CODE_POINT Character.MAX_CODE_POINT})</td></tr>
 112  * <tr><td valign="top" headers="matches"><tt>\t</tt></td>
 113  *     <td headers="matches">The tab character (<tt>'\u0009'</tt>)</td></tr>
 114  * <tr><td valign="top" headers="construct characters"><tt>\n</tt></td>
 115  *     <td headers="matches">The newline (line feed) character (<tt>'\u000A'</tt>)</td></tr>
 116  * <tr><td valign="top" headers="construct characters"><tt>\r</tt></td>
 117  *     <td headers="matches">The carriage-return character (<tt>'\u000D'</tt>)</td></tr>
 118  * <tr><td valign="top" headers="construct characters"><tt>\f</tt></td>
 119  *     <td headers="matches">The form-feed character (<tt>'\u000C'</tt>)</td></tr>
 120  * <tr><td valign="top" headers="construct characters"><tt>\a</tt></td>
 121  *     <td headers="matches">The alert (bell) character (<tt>'\u0007'</tt>)</td></tr>
 122  * <tr><td valign="top" headers="construct characters"><tt>\e</tt></td>
 123  *     <td headers="matches">The escape character (<tt>'\u001B'</tt>)</td></tr>
 124  * <tr><td valign="top" headers="construct characters"><tt>\c</tt><i>x</i></td>
 125  *     <td headers="matches">The control character corresponding to <i>x</i></td></tr>
 126  *
 127  * <tr><th>&nbsp;</th></tr>
 128  * <tr align="left"><th colspan="2" id="classes">Character classes</th></tr>
 129  *
 130  * <tr><td valign="top" headers="construct classes">{@code [abc]}</td>
 131  *     <td headers="matches">{@code a}, {@code b}, or {@code c} (simple class)</td></tr>
 132  * <tr><td valign="top" headers="construct classes">{@code [^abc]}</td>
 133  *     <td headers="matches">Any character except {@code a}, {@code b}, or {@code c} (negation)</td></tr>
 134  * <tr><td valign="top" headers="construct classes">{@code [a-zA-Z]}</td>
 135  *     <td headers="matches">{@code a} through {@code z}
 136  *         or {@code A} through {@code Z}, inclusive (range)</td></tr>
 137  * <tr><td valign="top" headers="construct classes">{@code [a-d[m-p]]}</td>
 138  *     <td headers="matches">{@code a} through {@code d},
 139  *      or {@code m} through {@code p}: {@code [a-dm-p]} (union)</td></tr>
 140  * <tr><td valign="top" headers="construct classes">{@code [a-z&&[def]]}</td>
 141  *     <td headers="matches">{@code d}, {@code e}, or {@code f} (intersection)</tr>
 142  * <tr><td valign="top" headers="construct classes">{@code [a-z&&[^bc]]}</td>
 143  *     <td headers="matches">{@code a} through {@code z},
 144  *         except for {@code b} and {@code c}: {@code [ad-z]} (subtraction)</td></tr>
 145  * <tr><td valign="top" headers="construct classes">{@code [a-z&&[^m-p]]}</td>
 146  *     <td headers="matches">{@code a} through {@code z},
 147  *          and not {@code m} through {@code p}: {@code [a-lq-z]}(subtraction)</td></tr>
 148  * <tr><th>&nbsp;</th></tr>
 149  *
 150  * <tr align="left"><th colspan="2" id="predef">Predefined character classes</th></tr>
 151  *
 152  * <tr><td valign="top" headers="construct predef"><tt>.</tt></td>
 153  *     <td headers="matches">Any character (may or may not match <a href="#lt">line terminators</a>)</td></tr>
 154  * <tr><td valign="top" headers="construct predef"><tt>\d</tt></td>
 155  *     <td headers="matches">A digit: <tt>[0-9]</tt></td></tr>
 156  * <tr><td valign="top" headers="construct predef"><tt>\D</tt></td>
 157  *     <td headers="matches">A non-digit: <tt>[^0-9]</tt></td></tr>
 158  * <tr><td valign="top" headers="construct predef"><tt>\h</tt></td>
 159  *     <td headers="matches">A horizontal whitespace character:
 160  *     <tt>[ \t\xA0\u1680\u180e\u2000-\u200a\u202f\u205f\u3000]</tt></td></tr>
 161  * <tr><td valign="top" headers="construct predef"><tt>\H</tt></td>
 162  *     <td headers="matches">A non-horizontal whitespace character: <tt>[^\h]</tt></td></tr>
 163  * <tr><td valign="top" headers="construct predef"><tt>\s</tt></td>
 164  *     <td headers="matches">A whitespace character: <tt>[ \t\n\x0B\f\r]</tt></td></tr>
 165  * <tr><td valign="top" headers="construct predef"><tt>\S</tt></td>
 166  *     <td headers="matches">A non-whitespace character: <tt>[^\s]</tt></td></tr>
 167  * <tr><td valign="top" headers="construct predef"><tt>\v</tt></td>
 168  *     <td headers="matches">A vertical whitespace character: <tt>[\n\x0B\f\r\x85\u2028\u2029]</tt>
 169  *     </td></tr>
 170  * <tr><td valign="top" headers="construct predef"><tt>\V</tt></td>
 171  *     <td headers="matches">A non-vertical whitespace character: <tt>[^\v]</tt></td></tr>
 172  * <tr><td valign="top" headers="construct predef"><tt>\w</tt></td>
 173  *     <td headers="matches">A word character: <tt>[a-zA-Z_0-9]</tt></td></tr>
 174  * <tr><td valign="top" headers="construct predef"><tt>\W</tt></td>
 175  *     <td headers="matches">A non-word character: <tt>[^\w]</tt></td></tr>
 176  * <tr><th>&nbsp;</th></tr>
 177  * <tr align="left"><th colspan="2" id="posix"><b>POSIX character classes (US-ASCII only)</b></th></tr>
 178  *
 179  * <tr><td valign="top" headers="construct posix">{@code \p{Lower}}</td>
 180  *     <td headers="matches">A lower-case alphabetic character: {@code [a-z]}</td></tr>
 181  * <tr><td valign="top" headers="construct posix">{@code \p{Upper}}</td>
 182  *     <td headers="matches">An upper-case alphabetic character:{@code [A-Z]}</td></tr>
 183  * <tr><td valign="top" headers="construct posix">{@code \p{ASCII}}</td>
 184  *     <td headers="matches">All ASCII:{@code [\x00-\x7F]}</td></tr>
 185  * <tr><td valign="top" headers="construct posix">{@code \p{Alpha}}</td>
 186  *     <td headers="matches">An alphabetic character:{@code [\p{Lower}\p{Upper}]}</td></tr>
 187  * <tr><td valign="top" headers="construct posix">{@code \p{Digit}}</td>
 188  *     <td headers="matches">A decimal digit: {@code [0-9]}</td></tr>
 189  * <tr><td valign="top" headers="construct posix">{@code \p{Alnum}}</td>
 190  *     <td headers="matches">An alphanumeric character:{@code [\p{Alpha}\p{Digit}]}</td></tr>
 191  * <tr><td valign="top" headers="construct posix">{@code \p{Punct}}</td>
 192  *     <td headers="matches">Punctuation: One of {@code !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~}</td></tr>
 193  *     <!-- {@code [\!"#\$%&'\(\)\*\+,\-\./:;\<=\>\?@\[\\\]\^_`\{\|\}~]}
 194  *          {@code [\X21-\X2F\X31-\X40\X5B-\X60\X7B-\X7E]} -->
 195  * <tr><td valign="top" headers="construct posix">{@code \p{Graph}}</td>
 196  *     <td headers="matches">A visible character: {@code [\p{Alnum}\p{Punct}]}</td></tr>
 197  * <tr><td valign="top" headers="construct posix">{@code \p{Print}}</td>
 198  *     <td headers="matches">A printable character: {@code [\p{Graph}\x20]}</td></tr>
 199  * <tr><td valign="top" headers="construct posix">{@code \p{Blank}}</td>
 200  *     <td headers="matches">A space or a tab: {@code [ \t]}</td></tr>
 201  * <tr><td valign="top" headers="construct posix">{@code \p{Cntrl}}</td>
 202  *     <td headers="matches">A control character: {@code [\x00-\x1F\x7F]}</td></tr>
 203  * <tr><td valign="top" headers="construct posix">{@code \p{XDigit}}</td>
 204  *     <td headers="matches">A hexadecimal digit: {@code [0-9a-fA-F]}</td></tr>
 205  * <tr><td valign="top" headers="construct posix">{@code \p{Space}}</td>
 206  *     <td headers="matches">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
 207  *
 208  * <tr><th>&nbsp;</th></tr>
 209  * <tr align="left"><th colspan="2">java.lang.Character classes (simple <a href="#jcc">java character type</a>)</th></tr>
 210  *
 211  * <tr><td valign="top"><tt>\p{javaLowerCase}</tt></td>
 212  *     <td>Equivalent to java.lang.Character.isLowerCase()</td></tr>
 213  * <tr><td valign="top"><tt>\p{javaUpperCase}</tt></td>
 214  *     <td>Equivalent to java.lang.Character.isUpperCase()</td></tr>
 215  * <tr><td valign="top"><tt>\p{javaWhitespace}</tt></td>
 216  *     <td>Equivalent to java.lang.Character.isWhitespace()</td></tr>
 217  * <tr><td valign="top"><tt>\p{javaMirrored}</tt></td>
 218  *     <td>Equivalent to java.lang.Character.isMirrored()</td></tr>
 219  *
 220  * <tr><th>&nbsp;</th></tr>
 221  * <tr align="left"><th colspan="2" id="unicode">Classes for Unicode scripts, blocks, categories and binary properties</th></tr>
 222  * <tr><td valign="top" headers="construct unicode">{@code \p{IsLatin}}</td>
 223  *     <td headers="matches">A Latin&nbsp;script character (<a href="#usc">script</a>)</td></tr>
 224  * <tr><td valign="top" headers="construct unicode">{@code \p{InGreek}}</td>
 225  *     <td headers="matches">A character in the Greek&nbsp;block (<a href="#ubc">block</a>)</td></tr>
 226  * <tr><td valign="top" headers="construct unicode">{@code \p{Lu}}</td>
 227  *     <td headers="matches">An uppercase letter (<a href="#ucc">category</a>)</td></tr>
 228  * <tr><td valign="top" headers="construct unicode">{@code \p{IsAlphabetic}}</td>
 229  *     <td headers="matches">An alphabetic character (<a href="#ubpc">binary property</a>)</td></tr>
 230  * <tr><td valign="top" headers="construct unicode">{@code \p{Sc}}</td>
 231  *     <td headers="matches">A currency symbol</td></tr>
 232  * <tr><td valign="top" headers="construct unicode">{@code \P{InGreek}}</td>
 233  *     <td headers="matches">Any character except one in the Greek block (negation)</td></tr>
 234  * <tr><td valign="top" headers="construct unicode">{@code [\p{L}&&[^\p{Lu}]]}</td>
 235  *     <td headers="matches">Any letter except an uppercase letter (subtraction)</td></tr>
 236  *
 237  * <tr><th>&nbsp;</th></tr>
 238  * <tr align="left"><th colspan="2" id="bounds">Boundary matchers</th></tr>
 239  *
 240  * <tr><td valign="top" headers="construct bounds"><tt>^</tt></td>
 241  *     <td headers="matches">The beginning of a line</td></tr>
 242  * <tr><td valign="top" headers="construct bounds"><tt>$</tt></td>
 243  *     <td headers="matches">The end of a line</td></tr>
 244  * <tr><td valign="top" headers="construct bounds"><tt>\b</tt></td>
 245  *     <td headers="matches">A word boundary</td></tr>
 246  * <tr><td valign="top" headers="construct bounds"><tt>\B</tt></td>
 247  *     <td headers="matches">A non-word boundary</td></tr>
 248  * <tr><td valign="top" headers="construct bounds"><tt>\A</tt></td>
 249  *     <td headers="matches">The beginning of the input</td></tr>
 250  * <tr><td valign="top" headers="construct bounds"><tt>\G</tt></td>
 251  *     <td headers="matches">The end of the previous match</td></tr>
 252  * <tr><td valign="top" headers="construct bounds"><tt>\Z</tt></td>
 253  *     <td headers="matches">The end of the input but for the final
 254  *         <a href="#lt">terminator</a>, if&nbsp;any</td></tr>
 255  * <tr><td valign="top" headers="construct bounds"><tt>\z</tt></td>
 256  *     <td headers="matches">The end of the input</td></tr>
 257  *
 258  * <tr><th>&nbsp;</th></tr>
 259  * <tr align="left"><th colspan="2" id="lineending">Linebreak matcher</th></tr>
 260  * <tr><td valign="top" headers="construct lineending"><tt>\R</tt></td>
 261  *     <td headers="matches">Any Unicode linebreak sequence, is equivalent to
 262  *     <tt>\u000D\u000A|[\u000A\u000B\u000C\u000D\u0085\u2028\u2029]
 263  *     </tt></td></tr>
 264  *
 265  * <tr><th>&nbsp;</th></tr>
 266  * <tr align="left"><th colspan="2" id="greedy">Greedy quantifiers</th></tr>
 267  *
 268  * <tr><td valign="top" headers="construct greedy"><i>X</i><tt>?</tt></td>
 269  *     <td headers="matches"><i>X</i>, once or not at all</td></tr>
 270  * <tr><td valign="top" headers="construct greedy"><i>X</i><tt>*</tt></td>
 271  *     <td headers="matches"><i>X</i>, zero or more times</td></tr>
 272  * <tr><td valign="top" headers="construct greedy"><i>X</i><tt>+</tt></td>
 273  *     <td headers="matches"><i>X</i>, one or more times</td></tr>
 274  * <tr><td valign="top" headers="construct greedy"><i>X</i><tt>{</tt><i>n</i><tt>}</tt></td>
 275  *     <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
 276  * <tr><td valign="top" headers="construct greedy"><i>X</i><tt>{</tt><i>n</i><tt>,}</tt></td>
 277  *     <td headers="matches"><i>X</i>, at least <i>n</i> times</td></tr>
 278  * <tr><td valign="top" headers="construct greedy"><i>X</i><tt>{</tt><i>n</i><tt>,</tt><i>m</i><tt>}</tt></td>
 279  *     <td headers="matches"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
 280  *
 281  * <tr><th>&nbsp;</th></tr>
 282  * <tr align="left"><th colspan="2" id="reluc">Reluctant quantifiers</th></tr>
 283  *
 284  * <tr><td valign="top" headers="construct reluc"><i>X</i><tt>??</tt></td>
 285  *     <td headers="matches"><i>X</i>, once or not at all</td></tr>
 286  * <tr><td valign="top" headers="construct reluc"><i>X</i><tt>*?</tt></td>
 287  *     <td headers="matches"><i>X</i>, zero or more times</td></tr>
 288  * <tr><td valign="top" headers="construct reluc"><i>X</i><tt>+?</tt></td>
 289  *     <td headers="matches"><i>X</i>, one or more times</td></tr>
 290  * <tr><td valign="top" headers="construct reluc"><i>X</i><tt>{</tt><i>n</i><tt>}?</tt></td>
 291  *     <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
 292  * <tr><td valign="top" headers="construct reluc"><i>X</i><tt>{</tt><i>n</i><tt>,}?</tt></td>
 293  *     <td headers="matches"><i>X</i>, at least <i>n</i> times</td></tr>
 294  * <tr><td valign="top" headers="construct reluc"><i>X</i><tt>{</tt><i>n</i><tt>,</tt><i>m</i><tt>}?</tt></td>
 295  *     <td headers="matches"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
 296  *
 297  * <tr><th>&nbsp;</th></tr>
 298  * <tr align="left"><th colspan="2" id="poss">Possessive quantifiers</th></tr>
 299  *
 300  * <tr><td valign="top" headers="construct poss"><i>X</i><tt>?+</tt></td>
 301  *     <td headers="matches"><i>X</i>, once or not at all</td></tr>
 302  * <tr><td valign="top" headers="construct poss"><i>X</i><tt>*+</tt></td>
 303  *     <td headers="matches"><i>X</i>, zero or more times</td></tr>
 304  * <tr><td valign="top" headers="construct poss"><i>X</i><tt>++</tt></td>
 305  *     <td headers="matches"><i>X</i>, one or more times</td></tr>
 306  * <tr><td valign="top" headers="construct poss"><i>X</i><tt>{</tt><i>n</i><tt>}+</tt></td>
 307  *     <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
 308  * <tr><td valign="top" headers="construct poss"><i>X</i><tt>{</tt><i>n</i><tt>,}+</tt></td>
 309  *     <td headers="matches"><i>X</i>, at least <i>n</i> times</td></tr>
 310  * <tr><td valign="top" headers="construct poss"><i>X</i><tt>{</tt><i>n</i><tt>,</tt><i>m</i><tt>}+</tt></td>
 311  *     <td headers="matches"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
 312  *
 313  * <tr><th>&nbsp;</th></tr>
 314  * <tr align="left"><th colspan="2" id="logical">Logical operators</th></tr>
 315  *
 316  * <tr><td valign="top" headers="construct logical"><i>XY</i></td>
 317  *     <td headers="matches"><i>X</i> followed by <i>Y</i></td></tr>
 318  * <tr><td valign="top" headers="construct logical"><i>X</i><tt>|</tt><i>Y</i></td>
 319  *     <td headers="matches">Either <i>X</i> or <i>Y</i></td></tr>
 320  * <tr><td valign="top" headers="construct logical"><tt>(</tt><i>X</i><tt>)</tt></td>
 321  *     <td headers="matches">X, as a <a href="#cg">capturing group</a></td></tr>
 322  *
 323  * <tr><th>&nbsp;</th></tr>
 324  * <tr align="left"><th colspan="2" id="backref">Back references</th></tr>
 325  *
 326  * <tr><td valign="bottom" headers="construct backref"><tt>\</tt><i>n</i></td>
 327  *     <td valign="bottom" headers="matches">Whatever the <i>n</i><sup>th</sup>
 328  *     <a href="#cg">capturing group</a> matched</td></tr>
 329  *
 330  * <tr><td valign="bottom" headers="construct backref"><tt>\</tt><i>k</i>&lt;<i>name</i>&gt;</td>
 331  *     <td valign="bottom" headers="matches">Whatever the
 332  *     <a href="#groupname">named-capturing group</a> "name" matched</td></tr>
 333  *
 334  * <tr><th>&nbsp;</th></tr>
 335  * <tr align="left"><th colspan="2" id="quot">Quotation</th></tr>
 336  *
 337  * <tr><td valign="top" headers="construct quot"><tt>\</tt></td>
 338  *     <td headers="matches">Nothing, but quotes the following character</td></tr>
 339  * <tr><td valign="top" headers="construct quot"><tt>\Q</tt></td>
 340  *     <td headers="matches">Nothing, but quotes all characters until <tt>\E</tt></td></tr>
 341  * <tr><td valign="top" headers="construct quot"><tt>\E</tt></td>
 342  *     <td headers="matches">Nothing, but ends quoting started by <tt>\Q</tt></td></tr>
 343  *     <!-- Metachars: !$()*+.<>?[\]^{|} -->
 344  *
 345  * <tr><th>&nbsp;</th></tr>
 346  * <tr align="left"><th colspan="2" id="special">Special constructs (named-capturing and non-capturing)</th></tr>
 347  *
 348  * <tr><td valign="top" headers="construct special"><tt>(?&lt;<a href="#groupname">name</a>&gt;</tt><i>X</i><tt>)</tt></td>
 349  *     <td headers="matches"><i>X</i>, as a named-capturing group</td></tr>
 350  * <tr><td valign="top" headers="construct special"><tt>(?:</tt><i>X</i><tt>)</tt></td>
 351  *     <td headers="matches"><i>X</i>, as a non-capturing group</td></tr>
 352  * <tr><td valign="top" headers="construct special"><tt>(?idmsuxU-idmsuxU)&nbsp;</tt></td>
 353  *     <td headers="matches">Nothing, but turns match flags <a href="#CASE_INSENSITIVE">i</a>
 354  * <a href="#UNIX_LINES">d</a> <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a>
 355  * <a href="#UNICODE_CASE">u</a> <a href="#COMMENTS">x</a> <a href="#UNICODE_CHARACTER_CLASS">U</a>
 356  * on - off</td></tr>
 357  * <tr><td valign="top" headers="construct special"><tt>(?idmsux-idmsux:</tt><i>X</i><tt>)</tt>&nbsp;&nbsp;</td>
 358  *     <td headers="matches"><i>X</i>, as a <a href="#cg">non-capturing group</a> with the
 359  *         given flags <a href="#CASE_INSENSITIVE">i</a> <a href="#UNIX_LINES">d</a>
 360  * <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a> <a href="#UNICODE_CASE">u</a >
 361  * <a href="#COMMENTS">x</a> on - off</td></tr>
 362  * <tr><td valign="top" headers="construct special"><tt>(?=</tt><i>X</i><tt>)</tt></td>
 363  *     <td headers="matches"><i>X</i>, via zero-width positive lookahead</td></tr>
 364  * <tr><td valign="top" headers="construct special"><tt>(?!</tt><i>X</i><tt>)</tt></td>
 365  *     <td headers="matches"><i>X</i>, via zero-width negative lookahead</td></tr>
 366  * <tr><td valign="top" headers="construct special"><tt>(?&lt;=</tt><i>X</i><tt>)</tt></td>
 367  *     <td headers="matches"><i>X</i>, via zero-width positive lookbehind</td></tr>
 368  * <tr><td valign="top" headers="construct special"><tt>(?&lt;!</tt><i>X</i><tt>)</tt></td>
 369  *     <td headers="matches"><i>X</i>, via zero-width negative lookbehind</td></tr>
 370  * <tr><td valign="top" headers="construct special"><tt>(?&gt;</tt><i>X</i><tt>)</tt></td>
 371  *     <td headers="matches"><i>X</i>, as an independent, non-capturing group</td></tr>
 372  *
 373  * </table>
 374  *
 375  * <hr>
 376  *
 377  *
 378  * <h3><a name="bs">Backslashes, escapes, and quoting</a></h3>
 379  *
 380  * <p> The backslash character (<tt>'\'</tt>) serves to introduce escaped
 381  * constructs, as defined in the table above, as well as to quote characters
 382  * that otherwise would be interpreted as unescaped constructs.  Thus the
 383  * expression <tt>\\</tt> matches a single backslash and <tt>\{</tt> matches a
 384  * left brace.
 385  *
 386  * <p> It is an error to use a backslash prior to any alphabetic character that
 387  * does not denote an escaped construct; these are reserved for future
 388  * extensions to the regular-expression language.  A backslash may be used
 389  * prior to a non-alphabetic character regardless of whether that character is
 390  * part of an unescaped construct.
 391  *
 392  * <p> Backslashes within string literals in Java source code are interpreted
 393  * as required by
 394  * <cite>The Java&trade; Language Specification</cite>
 395  * as either Unicode escapes (section 3.3) or other character escapes (section 3.10.6)
 396  * It is therefore necessary to double backslashes in string
 397  * literals that represent regular expressions to protect them from
 398  * interpretation by the Java bytecode compiler.  The string literal
 399  * <tt>"\b"</tt>, for example, matches a single backspace character when
 400  * interpreted as a regular expression, while <tt>"\\b"</tt> matches a
 401  * word boundary.  The string literal <tt>"\(hello\)"</tt> is illegal
 402  * and leads to a compile-time error; in order to match the string
 403  * <tt>(hello)</tt> the string literal <tt>"\\(hello\\)"</tt>
 404  * must be used.
 405  *
 406  * <h3><a name="cc">Character Classes</a></h3>
 407  *
 408  *    <p> Character classes may appear within other character classes, and
 409  *    may be composed by the union operator (implicit) and the intersection
 410  *    operator (<tt>&amp;&amp;</tt>).
 411  *    The union operator denotes a class that contains every character that is
 412  *    in at least one of its operand classes.  The intersection operator
 413  *    denotes a class that contains every character that is in both of its
 414  *    operand classes.
 415  *
 416  *    <p> The precedence of character-class operators is as follows, from
 417  *    highest to lowest:
 418  *
 419  *    <blockquote><table border="0" cellpadding="1" cellspacing="0"
 420  *                 summary="Precedence of character class operators.">
 421  *      <tr><th>1&nbsp;&nbsp;&nbsp;&nbsp;</th>
 422  *        <td>Literal escape&nbsp;&nbsp;&nbsp;&nbsp;</td>
 423  *        <td><tt>\x</tt></td></tr>
 424  *     <tr><th>2&nbsp;&nbsp;&nbsp;&nbsp;</th>
 425  *        <td>Grouping</td>
 426  *        <td><tt>[...]</tt></td></tr>
 427  *     <tr><th>3&nbsp;&nbsp;&nbsp;&nbsp;</th>
 428  *        <td>Range</td>
 429  *        <td><tt>a-z</tt></td></tr>
 430  *      <tr><th>4&nbsp;&nbsp;&nbsp;&nbsp;</th>
 431  *        <td>Union</td>
 432  *        <td><tt>[a-e][i-u]</tt></td></tr>
 433  *      <tr><th>5&nbsp;&nbsp;&nbsp;&nbsp;</th>
 434  *        <td>Intersection</td>
 435  *        <td>{@code [a-z&&[aeiou]]}</td></tr>
 436  *    </table></blockquote>
 437  *
 438  *    <p> Note that a different set of metacharacters are in effect inside
 439  *    a character class than outside a character class. For instance, the
 440  *    regular expression <tt>.</tt> loses its special meaning inside a
 441  *    character class, while the expression <tt>-</tt> becomes a range
 442  *    forming metacharacter.
 443  *
 444  * <h3><a name="lt">Line terminators</a></h3>
 445  *
 446  * <p> A <i>line terminator</i> is a one- or two-character sequence that marks
 447  * the end of a line of the input character sequence.  The following are
 448  * recognized as line terminators:
 449  *
 450  * <ul>
 451  *
 452  *   <li> A newline (line feed) character&nbsp;(<tt>'\n'</tt>),
 453  *
 454  *   <li> A carriage-return character followed immediately by a newline
 455  *   character&nbsp;(<tt>"\r\n"</tt>),
 456  *
 457  *   <li> A standalone carriage-return character&nbsp;(<tt>'\r'</tt>),
 458  *
 459  *   <li> A next-line character&nbsp;(<tt>'\u0085'</tt>),
 460  *
 461  *   <li> A line-separator character&nbsp;(<tt>'\u2028'</tt>), or
 462  *
 463  *   <li> A paragraph-separator character&nbsp;(<tt>'\u2029</tt>).
 464  *
 465  * </ul>
 466  * <p>If {@link #UNIX_LINES} mode is activated, then the only line terminators
 467  * recognized are newline characters.
 468  *
 469  * <p> The regular expression <tt>.</tt> matches any character except a line
 470  * terminator unless the {@link #DOTALL} flag is specified.
 471  *
 472  * <p> By default, the regular expressions <tt>^</tt> and <tt>$</tt> ignore
 473  * line terminators and only match at the beginning and the end, respectively,
 474  * of the entire input sequence. If {@link #MULTILINE} mode is activated then
 475  * <tt>^</tt> matches at the beginning of input and after any line terminator
 476  * except at the end of input. When in {@link #MULTILINE} mode <tt>$</tt>
 477  * matches just before a line terminator or the end of the input sequence.
 478  *
 479  * <h3><a name="cg">Groups and capturing</a></h3>
 480  *
 481  * <h4><a name="gnumber">Group number</a></h4>
 482  * <p> Capturing groups are numbered by counting their opening parentheses from
 483  * left to right.  In the expression <tt>((A)(B(C)))</tt>, for example, there
 484  * are four such groups: </p>
 485  *
 486  * <blockquote><table cellpadding=1 cellspacing=0 summary="Capturing group numberings">
 487  * <tr><th>1&nbsp;&nbsp;&nbsp;&nbsp;</th>
 488  *     <td><tt>((A)(B(C)))</tt></td></tr>
 489  * <tr><th>2&nbsp;&nbsp;&nbsp;&nbsp;</th>
 490  *     <td><tt>(A)</tt></td></tr>
 491  * <tr><th>3&nbsp;&nbsp;&nbsp;&nbsp;</th>
 492  *     <td><tt>(B(C))</tt></td></tr>
 493  * <tr><th>4&nbsp;&nbsp;&nbsp;&nbsp;</th>
 494  *     <td><tt>(C)</tt></td></tr>
 495  * </table></blockquote>
 496  *
 497  * <p> Group zero always stands for the entire expression.
 498  *
 499  * <p> Capturing groups are so named because, during a match, each subsequence
 500  * of the input sequence that matches such a group is saved.  The captured
 501  * subsequence may be used later in the expression, via a back reference, and
 502  * may also be retrieved from the matcher once the match operation is complete.
 503  *
 504  * <h4><a name="groupname">Group name</a></h4>
 505  * <p>A capturing group can also be assigned a "name", a <tt>named-capturing group</tt>,
 506  * and then be back-referenced later by the "name". Group names are composed of
 507  * the following characters. The first character must be a <tt>letter</tt>.
 508  *
 509  * <ul>
 510  *   <li> The uppercase letters <tt>'A'</tt> through <tt>'Z'</tt>
 511  *        (<tt>'\u0041'</tt>&nbsp;through&nbsp;<tt>'\u005a'</tt>),
 512  *   <li> The lowercase letters <tt>'a'</tt> through <tt>'z'</tt>
 513  *        (<tt>'\u0061'</tt>&nbsp;through&nbsp;<tt>'\u007a'</tt>),
 514  *   <li> The digits <tt>'0'</tt> through <tt>'9'</tt>
 515  *        (<tt>'\u0030'</tt>&nbsp;through&nbsp;<tt>'\u0039'</tt>),
 516  * </ul>
 517  *
 518  * <p> A <tt>named-capturing group</tt> is still numbered as described in
 519  * <a href="#gnumber">Group number</a>.
 520  *
 521  * <p> The captured input associated with a group is always the subsequence
 522  * that the group most recently matched.  If a group is evaluated a second time
 523  * because of quantification then its previously-captured value, if any, will
 524  * be retained if the second evaluation fails.  Matching the string
 525  * <tt>"aba"</tt> against the expression <tt>(a(b)?)+</tt>, for example, leaves
 526  * group two set to <tt>"b"</tt>.  All captured input is discarded at the
 527  * beginning of each match.
 528  *
 529  * <p> Groups beginning with <tt>(?</tt> are either pure, <i>non-capturing</i> groups
 530  * that do not capture text and do not count towards the group total, or
 531  * <i>named-capturing</i> group.
 532  *
 533  * <h3> Unicode support </h3>
 534  *
 535  * <p> This class is in conformance with Level 1 of <a
 536  * href="http://www.unicode.org/reports/tr18/"><i>Unicode Technical
 537  * Standard #18: Unicode Regular Expression</i></a>, plus RL2.1
 538  * Canonical Equivalents.
 539  * <p>
 540  * <b>Unicode escape sequences</b> such as <tt>\u2014</tt> in Java source code
 541  * are processed as described in section 3.3 of
 542  * <cite>The Java&trade; Language Specification</cite>.
 543  * Such escape sequences are also implemented directly by the regular-expression
 544  * parser so that Unicode escapes can be used in expressions that are read from
 545  * files or from the keyboard.  Thus the strings <tt>"\u2014"</tt> and
 546  * <tt>"\\u2014"</tt>, while not equal, compile into the same pattern, which
 547  * matches the character with hexadecimal value <tt>0x2014</tt>.
 548  * <p>
 549  * A Unicode character can also be represented in a regular-expression by
 550  * using its <b>Hex notation</b>(hexadecimal code point value) directly as described in construct
 551  * <tt>\x{...}</tt>, for example a supplementary character U+2011F
 552  * can be specified as <tt>\x{2011F}</tt>, instead of two consecutive
 553  * Unicode escape sequences of the surrogate pair
 554  * <tt>\uD840</tt><tt>\uDD1F</tt>.
 555  * <p>
 556  * Unicode scripts, blocks, categories and binary properties are written with
 557  * the <tt>\p</tt> and <tt>\P</tt> constructs as in Perl.
 558  * <tt>\p{</tt><i>prop</i><tt>}</tt> matches if
 559  * the input has the property <i>prop</i>, while <tt>\P{</tt><i>prop</i><tt>}</tt>
 560  * does not match if the input has that property.
 561  * <p>
 562  * Scripts, blocks, categories and binary properties can be used both inside
 563  * and outside of a character class.
 564  *
 565  * <p>
 566  * <b><a name="usc">Scripts</a></b> are specified either with the prefix {@code Is}, as in
 567  * {@code IsHiragana}, or by using  the {@code script} keyword (or its short
 568  * form {@code sc})as in {@code script=Hiragana} or {@code sc=Hiragana}.
 569  * <p>
 570  * The script names supported by <code>Pattern</code> are the valid script names
 571  * accepted and defined by
 572  * {@link java.lang.Character.UnicodeScript#forName(String) UnicodeScript.forName}.
 573  *
 574  * <p>
 575  * <b><a name="ubc">Blocks</a></b> are specified with the prefix {@code In}, as in
 576  * {@code InMongolian}, or by using the keyword {@code block} (or its short
 577  * form {@code blk}) as in {@code block=Mongolian} or {@code blk=Mongolian}.
 578  * <p>
 579  * The block names supported by <code>Pattern</code> are the valid block names
 580  * accepted and defined by
 581  * {@link java.lang.Character.UnicodeBlock#forName(String) UnicodeBlock.forName}.
 582  * <p>
 583  *
 584  * <b><a name="ucc">Categories</a></b> may be specified with the optional prefix {@code Is}:
 585  * Both {@code \p{L}} and {@code \p{IsL}} denote the category of Unicode
 586  * letters. Same as scripts and blocks, categories can also be specified
 587  * by using the keyword {@code general_category} (or its short form
 588  * {@code gc}) as in {@code general_category=Lu} or {@code gc=Lu}.
 589  * <p>
 590  * The supported categories are those of
 591  * <a href="http://www.unicode.org/unicode/standard/standard.html">
 592  * <i>The Unicode Standard</i></a> in the version specified by the
 593  * {@link java.lang.Character Character} class. The category names are those
 594  * defined in the Standard, both normative and informative.
 595  * <p>
 596  *
 597  * <b><a name="ubpc">Binary properties</a></b> are specified with the prefix {@code Is}, as in
 598  * {@code IsAlphabetic}. The supported binary properties by <code>Pattern</code>
 599  * are
 600  * <ul>
 601  *   <li> Alphabetic
 602  *   <li> Ideographic
 603  *   <li> Letter
 604  *   <li> Lowercase
 605  *   <li> Uppercase
 606  *   <li> Titlecase
 607  *   <li> Punctuation
 608  *   <Li> Control
 609  *   <li> White_Space
 610  *   <li> Digit
 611  *   <li> Hex_Digit
 612  *   <li> Join_Control
 613  *   <li> Noncharacter_Code_Point
 614  *   <li> Assigned
 615  * </ul>
 616  * <p>
 617  * The following <b>Predefined Character classes</b> and <b>POSIX character classes</b>
 618  * are in conformance with the recommendation of <i>Annex C: Compatibility Properties</i>
 619  * of <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Regular Expression
 620  * </i></a>, when {@link #UNICODE_CHARACTER_CLASS} flag is specified.
 621  *
 622  * <table border="0" cellpadding="1" cellspacing="0"
 623  *  summary="predefined and posix character classes in Unicode mode">
 624  * <tr align="left">
 625  * <th align="left" id="predef_classes">Classes</th>
 626  * <th align="left" id="predef_matches">Matches</th>
 627  *</tr>
 628  * <tr><td><tt>\p{Lower}</tt></td>
 629  *     <td>A lowercase character:<tt>\p{IsLowercase}</tt></td></tr>
 630  * <tr><td><tt>\p{Upper}</tt></td>
 631  *     <td>An uppercase character:<tt>\p{IsUppercase}</tt></td></tr>
 632  * <tr><td><tt>\p{ASCII}</tt></td>
 633  *     <td>All ASCII:<tt>[\x00-\x7F]</tt></td></tr>
 634  * <tr><td><tt>\p{Alpha}</tt></td>
 635  *     <td>An alphabetic character:<tt>\p{IsAlphabetic}</tt></td></tr>
 636  * <tr><td><tt>\p{Digit}</tt></td>
 637  *     <td>A decimal digit character:<tt>p{IsDigit}</tt></td></tr>
 638  * <tr><td><tt>\p{Alnum}</tt></td>
 639  *     <td>An alphanumeric character:<tt>[\p{IsAlphabetic}\p{IsDigit}]</tt></td></tr>
 640  * <tr><td><tt>\p{Punct}</tt></td>
 641  *     <td>A punctuation character:<tt>p{IsPunctuation}</tt></td></tr>
 642  * <tr><td><tt>\p{Graph}</tt></td>
 643  *     <td>A visible character: <tt>[^\p{IsWhite_Space}\p{gc=Cc}\p{gc=Cs}\p{gc=Cn}]</tt></td></tr>
 644  * <tr><td><tt>\p{Print}</tt></td>
 645  *     <td>A printable character: {@code [\p{Graph}\p{Blank}&&[^\p{Cntrl}]]}</td></tr>
 646  * <tr><td><tt>\p{Blank}</tt></td>
 647  *     <td>A space or a tab: {@code [\p{IsWhite_Space}&&[^\p{gc=Zl}\p{gc=Zp}\x0a\x0b\x0c\x0d\x85]]}</td></tr>
 648  * <tr><td><tt>\p{Cntrl}</tt></td>
 649  *     <td>A control character: <tt>\p{gc=Cc}</tt></td></tr>
 650  * <tr><td><tt>\p{XDigit}</tt></td>
 651  *     <td>A hexadecimal digit: <tt>[\p{gc=Nd}\p{IsHex_Digit}]</tt></td></tr>
 652  * <tr><td><tt>\p{Space}</tt></td>
 653  *     <td>A whitespace character:<tt>\p{IsWhite_Space}</tt></td></tr>
 654  * <tr><td><tt>\d</tt></td>
 655  *     <td>A digit: <tt>\p{IsDigit}</tt></td></tr>
 656  * <tr><td><tt>\D</tt></td>
 657  *     <td>A non-digit: <tt>[^\d]</tt></td></tr>
 658  * <tr><td><tt>\s</tt></td>
 659  *     <td>A whitespace character: <tt>\p{IsWhite_Space}</tt></td></tr>
 660  * <tr><td><tt>\S</tt></td>
 661  *     <td>A non-whitespace character: <tt>[^\s]</tt></td></tr>
 662  * <tr><td><tt>\w</tt></td>
 663  *     <td>A word character: <tt>[\p{Alpha}\p{gc=Mn}\p{gc=Me}\p{gc=Mc}\p{Digit}\p{gc=Pc}\p{IsJoin_Control}]</tt></td></tr>
 664  * <tr><td><tt>\W</tt></td>
 665  *     <td>A non-word character: <tt>[^\w]</tt></td></tr>
 666  * </table>
 667  * <p>
 668  * <a name="jcc">
 669  * Categories that behave like the java.lang.Character
 670  * boolean is<i>methodname</i> methods (except for the deprecated ones) are
 671  * available through the same <tt>\p{</tt><i>prop</i><tt>}</tt> syntax where
 672  * the specified property has the name <tt>java<i>methodname</i></tt></a>.
 673  *
 674  * <h3> Comparison to Perl 5 </h3>
 675  *
 676  * <p>The <code>Pattern</code> engine performs traditional NFA-based matching
 677  * with ordered alternation as occurs in Perl 5.
 678  *
 679  * <p> Perl constructs not supported by this class: </p>
 680  *
 681  * <ul>
 682  *    <li><p> Predefined character classes (Unicode character)
 683  *    <p><tt>\X&nbsp;&nbsp;&nbsp;&nbsp;</tt>Match Unicode
 684  *    <a href="http://www.unicode.org/reports/tr18/#Default_Grapheme_Clusters">
 685  *    <i>extended grapheme cluster</i></a>
 686  *    </p></li>
 687  *
 688  *    <li><p> The backreference constructs, <tt>\g{</tt><i>n</i><tt>}</tt> for
 689  *    the <i>n</i><sup>th</sup><a href="#cg">capturing group</a> and
 690  *    <tt>\g{</tt><i>name</i><tt>}</tt> for
 691  *    <a href="#groupname">named-capturing group</a>.
 692  *    </p></li>
 693  *
 694  *    <li><p> The named character construct, <tt>\N{</tt><i>name</i><tt>}</tt>
 695  *    for a Unicode character by its name.
 696  *    </p></li>
 697  *
 698  *    <li><p> The conditional constructs
 699  *    <tt>(?(</tt><i>condition</i><tt>)</tt><i>X</i><tt>)</tt> and
 700  *    <tt>(?(</tt><i>condition</i><tt>)</tt><i>X</i><tt>|</tt><i>Y</i><tt>)</tt>,
 701  *    </p></li>
 702  *
 703  *    <li><p> The embedded code constructs <tt>(?{</tt><i>code</i><tt>})</tt>
 704  *    and <tt>(??{</tt><i>code</i><tt>})</tt>,</p></li>
 705  *
 706  *    <li><p> The embedded comment syntax <tt>(?#comment)</tt>, and </p></li>
 707  *
 708  *    <li><p> The preprocessing operations <tt>\l</tt> <tt>\u</tt>,
 709  *    <tt>\L</tt>, and <tt>\U</tt>.  </p></li>
 710  *
 711  * </ul>
 712  *
 713  * <p> Constructs supported by this class but not by Perl: </p>
 714  *
 715  * <ul>
 716  *
 717  *    <li><p> Character-class union and intersection as described
 718  *    <a href="#cc">above</a>.</p></li>
 719  *
 720  * </ul>
 721  *
 722  * <p> Notable differences from Perl: </p>
 723  *
 724  * <ul>
 725  *
 726  *    <li><p> In Perl, <tt>\1</tt> through <tt>\9</tt> are always interpreted
 727  *    as back references; a backslash-escaped number greater than <tt>9</tt> is
 728  *    treated as a back reference if at least that many subexpressions exist,
 729  *    otherwise it is interpreted, if possible, as an octal escape.  In this
 730  *    class octal escapes must always begin with a zero. In this class,
 731  *    <tt>\1</tt> through <tt>\9</tt> are always interpreted as back
 732  *    references, and a larger number is accepted as a back reference if at
 733  *    least that many subexpressions exist at that point in the regular
 734  *    expression, otherwise the parser will drop digits until the number is
 735  *    smaller or equal to the existing number of groups or it is one digit.
 736  *    </p></li>
 737  *
 738  *    <li><p> Perl uses the <tt>g</tt> flag to request a match that resumes
 739  *    where the last match left off.  This functionality is provided implicitly
 740  *    by the {@link Matcher} class: Repeated invocations of the {@link
 741  *    Matcher#find find} method will resume where the last match left off,
 742  *    unless the matcher is reset.  </p></li>
 743  *
 744  *    <li><p> In Perl, embedded flags at the top level of an expression affect
 745  *    the whole expression.  In this class, embedded flags always take effect
 746  *    at the point at which they appear, whether they are at the top level or
 747  *    within a group; in the latter case, flags are restored at the end of the
 748  *    group just as in Perl.  </p></li>
 749  *
 750  * </ul>
 751  *
 752  *
 753  * <p> For a more precise description of the behavior of regular expression
 754  * constructs, please see <a href="http://www.oreilly.com/catalog/regex3/">
 755  * <i>Mastering Regular Expressions, 3nd Edition</i>, Jeffrey E. F. Friedl,
 756  * O'Reilly and Associates, 2006.</a>
 757  * </p>
 758  *
 759  * @see java.lang.String#split(String, int)
 760  * @see java.lang.String#split(String)
 761  *
 762  * @author      Mike McCloskey
 763  * @author      Mark Reinhold
 764  * @author      JSR-51 Expert Group
 765  * @since       1.4
 766  * @spec        JSR-51
 767  */
 768 
 769 public final class Pattern
 770     implements java.io.Serializable
 771 {
 772 
 773     /**
 774      * Regular expression modifier values.  Instead of being passed as
 775      * arguments, they can also be passed as inline modifiers.
 776      * For example, the following statements have the same effect.
 777      * <pre>
 778      * RegExp r1 = RegExp.compile("abc", Pattern.I|Pattern.M);
 779      * RegExp r2 = RegExp.compile("(?im)abc", 0);
 780      * </pre>
 781      *
 782      * The flags are duplicated so that the familiar Perl match flag
 783      * names are available.
 784      */
 785 
 786     /**
 787      * Enables Unix lines mode.
 788      *
 789      * <p> In this mode, only the <tt>'\n'</tt> line terminator is recognized
 790      * in the behavior of <tt>.</tt>, <tt>^</tt>, and <tt>$</tt>.
 791      *
 792      * <p> Unix lines mode can also be enabled via the embedded flag
 793      * expression&nbsp;<tt>(?d)</tt>.
 794      */
 795     public static final int UNIX_LINES = 0x01;
 796 
 797     /**
 798      * Enables case-insensitive matching.
 799      *
 800      * <p> By default, case-insensitive matching assumes that only characters
 801      * in the US-ASCII charset are being matched.  Unicode-aware
 802      * case-insensitive matching can be enabled by specifying the {@link
 803      * #UNICODE_CASE} flag in conjunction with this flag.
 804      *
 805      * <p> Case-insensitive matching can also be enabled via the embedded flag
 806      * expression&nbsp;<tt>(?i)</tt>.
 807      *
 808      * <p> Specifying this flag may impose a slight performance penalty.  </p>
 809      */
 810     public static final int CASE_INSENSITIVE = 0x02;
 811 
 812     /**
 813      * Permits whitespace and comments in pattern.
 814      *
 815      * <p> In this mode, whitespace is ignored, and embedded comments starting
 816      * with <tt>#</tt> are ignored until the end of a line.
 817      *
 818      * <p> Comments mode can also be enabled via the embedded flag
 819      * expression&nbsp;<tt>(?x)</tt>.
 820      */
 821     public static final int COMMENTS = 0x04;
 822 
 823     /**
 824      * Enables multiline mode.
 825      *
 826      * <p> In multiline mode the expressions <tt>^</tt> and <tt>$</tt> match
 827      * just after or just before, respectively, a line terminator or the end of
 828      * the input sequence.  By default these expressions only match at the
 829      * beginning and the end of the entire input sequence.
 830      *
 831      * <p> Multiline mode can also be enabled via the embedded flag
 832      * expression&nbsp;<tt>(?m)</tt>.  </p>
 833      */
 834     public static final int MULTILINE = 0x08;
 835 
 836     /**
 837      * Enables literal parsing of the pattern.
 838      *
 839      * <p> When this flag is specified then the input string that specifies
 840      * the pattern is treated as a sequence of literal characters.
 841      * Metacharacters or escape sequences in the input sequence will be
 842      * given no special meaning.
 843      *
 844      * <p>The flags CASE_INSENSITIVE and UNICODE_CASE retain their impact on
 845      * matching when used in conjunction with this flag. The other flags
 846      * become superfluous.
 847      *
 848      * <p> There is no embedded flag character for enabling literal parsing.
 849      * @since 1.5
 850      */
 851     public static final int LITERAL = 0x10;
 852 
 853     /**
 854      * Enables dotall mode.
 855      *
 856      * <p> In dotall mode, the expression <tt>.</tt> matches any character,
 857      * including a line terminator.  By default this expression does not match
 858      * line terminators.
 859      *
 860      * <p> Dotall mode can also be enabled via the embedded flag
 861      * expression&nbsp;<tt>(?s)</tt>.  (The <tt>s</tt> is a mnemonic for
 862      * "single-line" mode, which is what this is called in Perl.)  </p>
 863      */
 864     public static final int DOTALL = 0x20;
 865 
 866     /**
 867      * Enables Unicode-aware case folding.
 868      *
 869      * <p> When this flag is specified then case-insensitive matching, when
 870      * enabled by the {@link #CASE_INSENSITIVE} flag, is done in a manner
 871      * consistent with the Unicode Standard.  By default, case-insensitive
 872      * matching assumes that only characters in the US-ASCII charset are being
 873      * matched.
 874      *
 875      * <p> Unicode-aware case folding can also be enabled via the embedded flag
 876      * expression&nbsp;<tt>(?u)</tt>.
 877      *
 878      * <p> Specifying this flag may impose a performance penalty.  </p>
 879      */
 880     public static final int UNICODE_CASE = 0x40;
 881 
 882     /**
 883      * Enables canonical equivalence.
 884      *
 885      * <p> When this flag is specified then two characters will be considered
 886      * to match if, and only if, their full canonical decompositions match.
 887      * The expression <tt>"a\u030A"</tt>, for example, will match the
 888      * string <tt>"\u00E5"</tt> when this flag is specified.  By default,
 889      * matching does not take canonical equivalence into account.
 890      *
 891      * <p> There is no embedded flag character for enabling canonical
 892      * equivalence.
 893      *
 894      * <p> Specifying this flag may impose a performance penalty.  </p>
 895      */
 896     public static final int CANON_EQ = 0x80;
 897 
 898     /**
 899      * Enables the Unicode version of <i>Predefined character classes</i> and
 900      * <i>POSIX character classes</i>.
 901      *
 902      * <p> When this flag is specified then the (US-ASCII only)
 903      * <i>Predefined character classes</i> and <i>POSIX character classes</i>
 904      * are in conformance with
 905      * <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Technical
 906      * Standard #18: Unicode Regular Expression</i></a>
 907      * <i>Annex C: Compatibility Properties</i>.
 908      * <p>
 909      * The UNICODE_CHARACTER_CLASS mode can also be enabled via the embedded
 910      * flag expression&nbsp;<tt>(?U)</tt>.
 911      * <p>
 912      * The flag implies UNICODE_CASE, that is, it enables Unicode-aware case
 913      * folding.
 914      * <p>
 915      * Specifying this flag may impose a performance penalty.  </p>
 916      * @since 1.7
 917      */
 918     public static final int UNICODE_CHARACTER_CLASS = 0x100;
 919 
 920     /**
 921      * Contains all possible flags for compile(regex, flags).
 922      */
 923     private static final int ALL_FLAGS = CASE_INSENSITIVE | MULTILINE |
 924             DOTALL | UNICODE_CASE | CANON_EQ | UNIX_LINES | LITERAL |
 925             UNICODE_CHARACTER_CLASS | COMMENTS;
 926 
 927     /* Pattern has only two serialized components: The pattern string
 928      * and the flags, which are all that is needed to recompile the pattern
 929      * when it is deserialized.
 930      */
 931 
 932     /** use serialVersionUID from Merlin b59 for interoperability */
 933     private static final long serialVersionUID = 5073258162644648461L;
 934 
 935     /**
 936      * The original regular-expression pattern string.
 937      *
 938      * @serial
 939      */
 940     private String pattern;
 941 
 942     /**
 943      * The original pattern flags.
 944      *
 945      * @serial
 946      */
 947     private int flags;
 948 
 949     /**
 950      * Boolean indicating this Pattern is compiled; this is necessary in order
 951      * to lazily compile deserialized Patterns.
 952      */
 953     private transient volatile boolean compiled = false;
 954 
 955     /**
 956      * The normalized pattern string.
 957      */
 958     private transient String normalizedPattern;
 959 
 960     /**
 961      * The starting point of state machine for the find operation.  This allows
 962      * a match to start anywhere in the input.
 963      */
 964     transient Node root;
 965 
 966     /**
 967      * The root of object tree for a match operation.  The pattern is matched
 968      * at the beginning.  This may include a find that uses BnM or a First
 969      * node.
 970      */
 971     transient Node matchRoot;
 972 
 973     /**
 974      * Temporary storage used by parsing pattern slice.
 975      */
 976     transient int[] buffer;
 977 
 978     /**
 979      * Map the "name" of the "named capturing group" to its group id
 980      * node.
 981      */
 982     transient volatile Map<String, Integer> namedGroups;
 983 
 984     /**
 985      * Temporary storage used while parsing group references.
 986      */
 987     transient GroupHead[] groupNodes;
 988 
 989     /**
 990      * Temporary null terminated code point array used by pattern compiling.
 991      */
 992     private transient int[] temp;
 993 
 994     /**
 995      * The number of capturing groups in this Pattern. Used by matchers to
 996      * allocate storage needed to perform a match.
 997      */
 998     transient int capturingGroupCount;
 999 
1000     /**
1001      * The local variable count used by parsing tree. Used by matchers to
1002      * allocate storage needed to perform a match.
1003      */
1004     transient int localCount;
1005 
1006     /**
1007      * Index into the pattern string that keeps track of how much has been
1008      * parsed.
1009      */
1010     private transient int cursor;
1011 
1012     /**
1013      * Holds the length of the pattern string.
1014      */
1015     private transient int patternLength;
1016 
1017     /**
1018      * If the Start node might possibly match supplementary characters.
1019      * It is set to true during compiling if
1020      * (1) There is supplementary char in pattern, or
1021      * (2) There is complement node of Category or Block
1022      */
1023     private transient boolean hasSupplementary;
1024 
1025     /**
1026      * Compiles the given regular expression into a pattern.
1027      *
1028      * @param  regex
1029      *         The expression to be compiled
1030      * @return the given regular expression compiled into a pattern
1031      * @throws  PatternSyntaxException
1032      *          If the expression's syntax is invalid
1033      */
1034     public static Pattern compile(String regex) {
1035         return new Pattern(regex, 0);
1036     }
1037 
1038     /**
1039      * Compiles the given regular expression into a pattern with the given
1040      * flags.
1041      *
1042      * @param  regex
1043      *         The expression to be compiled
1044      *
1045      * @param  flags
1046      *         Match flags, a bit mask that may include
1047      *         {@link #CASE_INSENSITIVE}, {@link #MULTILINE}, {@link #DOTALL},
1048      *         {@link #UNICODE_CASE}, {@link #CANON_EQ}, {@link #UNIX_LINES},
1049      *         {@link #LITERAL}, {@link #UNICODE_CHARACTER_CLASS}
1050      *         and {@link #COMMENTS}
1051      *
1052      * @return the given regular expression compiled into a pattern with the given flags
1053      * @throws  IllegalArgumentException
1054      *          If bit values other than those corresponding to the defined
1055      *          match flags are set in <tt>flags</tt>
1056      *
1057      * @throws  PatternSyntaxException
1058      *          If the expression's syntax is invalid
1059      */
1060     public static Pattern compile(String regex, int flags) {
1061         return new Pattern(regex, flags);
1062     }
1063 
1064     /**
1065      * Returns the regular expression from which this pattern was compiled.
1066      *
1067      * @return  The source of this pattern
1068      */
1069     public String pattern() {
1070         return pattern;
1071     }
1072 
1073     /**
1074      * <p>Returns the string representation of this pattern. This
1075      * is the regular expression from which this pattern was
1076      * compiled.</p>
1077      *
1078      * @return  The string representation of this pattern
1079      * @since 1.5
1080      */
1081     public String toString() {
1082         return pattern;
1083     }
1084 
1085     /**
1086      * Creates a matcher that will match the given input against this pattern.
1087      *
1088      * @param  input
1089      *         The character sequence to be matched
1090      *
1091      * @return  A new matcher for this pattern
1092      */
1093     public Matcher matcher(CharSequence input) {
1094         if (!compiled) {
1095             synchronized(this) {
1096                 if (!compiled)
1097                     compile();
1098             }
1099         }
1100         Matcher m = new Matcher(this, input);
1101         return m;
1102     }
1103 
1104     /**
1105      * Returns this pattern's match flags.
1106      *
1107      * @return  The match flags specified when this pattern was compiled
1108      */
1109     public int flags() {
1110         return flags;
1111     }
1112 
1113     /**
1114      * Compiles the given regular expression and attempts to match the given
1115      * input against it.
1116      *
1117      * <p> An invocation of this convenience method of the form
1118      *
1119      * <blockquote><pre>
1120      * Pattern.matches(regex, input);</pre></blockquote>
1121      *
1122      * behaves in exactly the same way as the expression
1123      *
1124      * <blockquote><pre>
1125      * Pattern.compile(regex).matcher(input).matches()</pre></blockquote>
1126      *
1127      * <p> If a pattern is to be used multiple times, compiling it once and reusing
1128      * it will be more efficient than invoking this method each time.  </p>
1129      *
1130      * @param  regex
1131      *         The expression to be compiled
1132      *
1133      * @param  input
1134      *         The character sequence to be matched
1135      * @return whether or not the regular expression matches on the input
1136      * @throws  PatternSyntaxException
1137      *          If the expression's syntax is invalid
1138      */
1139     public static boolean matches(String regex, CharSequence input) {
1140         Pattern p = Pattern.compile(regex);
1141         Matcher m = p.matcher(input);
1142         return m.matches();
1143     }
1144 
1145     /**
1146      * Splits the given input sequence around matches of this pattern.
1147      *
1148      * <p> The array returned by this method contains each substring of the
1149      * input sequence that is terminated by another subsequence that matches
1150      * this pattern or is terminated by the end of the input sequence.  The
1151      * substrings in the array are in the order in which they occur in the
1152      * input. If this pattern does not match any subsequence of the input then
1153      * the resulting array has just one element, namely the input sequence in
1154      * string form.
1155      *
1156      * <p> When there is a positive-width match at the beginning of the input
1157      * sequence then an empty leading substring is included at the beginning
1158      * of the resulting array. A zero-width match at the beginning however
1159      * never produces such empty leading substring.
1160      *
1161      * <p> The <tt>limit</tt> parameter controls the number of times the
1162      * pattern is applied and therefore affects the length of the resulting
1163      * array.  If the limit <i>n</i> is greater than zero then the pattern
1164      * will be applied at most <i>n</i>&nbsp;-&nbsp;1 times, the array's
1165      * length will be no greater than <i>n</i>, and the array's last entry
1166      * will contain all input beyond the last matched delimiter.  If <i>n</i>
1167      * is non-positive then the pattern will be applied as many times as
1168      * possible and the array can have any length.  If <i>n</i> is zero then
1169      * the pattern will be applied as many times as possible, the array can
1170      * have any length, and trailing empty strings will be discarded.
1171      *
1172      * <p> The input <tt>"boo:and:foo"</tt>, for example, yields the following
1173      * results with these parameters:
1174      *
1175      * <blockquote><table cellpadding=1 cellspacing=0
1176      *              summary="Split examples showing regex, limit, and result">
1177      * <tr><th align="left"><i>Regex&nbsp;&nbsp;&nbsp;&nbsp;</i></th>
1178      *     <th align="left"><i>Limit&nbsp;&nbsp;&nbsp;&nbsp;</i></th>
1179      *     <th align="left"><i>Result&nbsp;&nbsp;&nbsp;&nbsp;</i></th></tr>
1180      * <tr><td align=center>:</td>
1181      *     <td align=center>2</td>
1182      *     <td><tt>{ "boo", "and:foo" }</tt></td></tr>
1183      * <tr><td align=center>:</td>
1184      *     <td align=center>5</td>
1185      *     <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
1186      * <tr><td align=center>:</td>
1187      *     <td align=center>-2</td>
1188      *     <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
1189      * <tr><td align=center>o</td>
1190      *     <td align=center>5</td>
1191      *     <td><tt>{ "b", "", ":and:f", "", "" }</tt></td></tr>
1192      * <tr><td align=center>o</td>
1193      *     <td align=center>-2</td>
1194      *     <td><tt>{ "b", "", ":and:f", "", "" }</tt></td></tr>
1195      * <tr><td align=center>o</td>
1196      *     <td align=center>0</td>
1197      *     <td><tt>{ "b", "", ":and:f" }</tt></td></tr>
1198      * </table></blockquote>
1199      *
1200      * @param  input
1201      *         The character sequence to be split
1202      *
1203      * @param  limit
1204      *         The result threshold, as described above
1205      *
1206      * @return  The array of strings computed by splitting the input
1207      *          around matches of this pattern
1208      */
1209     public String[] split(CharSequence input, int limit) {
1210         int index = 0;
1211         boolean matchLimited = limit > 0;
1212         ArrayList<String> matchList = new ArrayList<>();
1213         Matcher m = matcher(input);
1214 
1215         // Add segments before each match found
1216         while(m.find()) {
1217             if (!matchLimited || matchList.size() < limit - 1) {
1218                 if (index == 0 && index == m.start() && m.start() == m.end()) {
1219                     // no empty leading substring included for zero-width match
1220                     // at the beginning of the input char sequence.
1221                     continue;
1222                 }
1223                 String match = input.subSequence(index, m.start()).toString();
1224                 matchList.add(match);
1225                 index = m.end();
1226             } else if (matchList.size() == limit - 1) { // last one
1227                 String match = input.subSequence(index,
1228                                                  input.length()).toString();
1229                 matchList.add(match);
1230                 index = m.end();
1231             }
1232         }
1233 
1234         // If no match was found, return this
1235         if (index == 0)
1236             return new String[] {input.toString()};
1237 
1238         // Add remaining segment
1239         if (!matchLimited || matchList.size() < limit)
1240             matchList.add(input.subSequence(index, input.length()).toString());
1241 
1242         // Construct result
1243         int resultSize = matchList.size();
1244         if (limit == 0)
1245             while (resultSize > 0 && matchList.get(resultSize-1).equals(""))
1246                 resultSize--;
1247         String[] result = new String[resultSize];
1248         return matchList.subList(0, resultSize).toArray(result);
1249     }
1250 
1251     /**
1252      * Splits the given input sequence around matches of this pattern.
1253      *
1254      * <p> This method works as if by invoking the two-argument {@link
1255      * #split(java.lang.CharSequence, int) split} method with the given input
1256      * sequence and a limit argument of zero.  Trailing empty strings are
1257      * therefore not included in the resulting array. </p>
1258      *
1259      * <p> The input <tt>"boo:and:foo"</tt>, for example, yields the following
1260      * results with these expressions:
1261      *
1262      * <blockquote><table cellpadding=1 cellspacing=0
1263      *              summary="Split examples showing regex and result">
1264      * <tr><th align="left"><i>Regex&nbsp;&nbsp;&nbsp;&nbsp;</i></th>
1265      *     <th align="left"><i>Result</i></th></tr>
1266      * <tr><td align=center>:</td>
1267      *     <td><tt>{ "boo", "and", "foo" }</tt></td></tr>
1268      * <tr><td align=center>o</td>
1269      *     <td><tt>{ "b", "", ":and:f" }</tt></td></tr>
1270      * </table></blockquote>
1271      *
1272      *
1273      * @param  input
1274      *         The character sequence to be split
1275      *
1276      * @return  The array of strings computed by splitting the input
1277      *          around matches of this pattern
1278      */
1279     public String[] split(CharSequence input) {
1280         return split(input, 0);
1281     }
1282 
1283     /**
1284      * Returns a literal pattern <code>String</code> for the specified
1285      * <code>String</code>.
1286      *
1287      * <p>This method produces a <code>String</code> that can be used to
1288      * create a <code>Pattern</code> that would match the string
1289      * <code>s</code> as if it were a literal pattern.</p> Metacharacters
1290      * or escape sequences in the input sequence will be given no special
1291      * meaning.
1292      *
1293      * @param  s The string to be literalized
1294      * @return  A literal string replacement
1295      * @since 1.5
1296      */
1297     public static String quote(String s) {
1298         int slashEIndex = s.indexOf("\\E");
1299         if (slashEIndex == -1)
1300             return "\\Q" + s + "\\E";
1301 
1302         StringBuilder sb = new StringBuilder(s.length() * 2);




1303         sb.append("\\Q");
1304         slashEIndex = 0;
1305         int current = 0;
1306         while ((slashEIndex = s.indexOf("\\E", current)) != -1) {
1307             sb.append(s.substring(current, slashEIndex));

1308             current = slashEIndex + 2;
1309             sb.append("\\E\\\\E\\Q");
1310         }
1311         sb.append(s.substring(current, s.length()));
1312         sb.append("\\E");
1313         return sb.toString();
1314     }
1315 
1316     /**
1317      * Recompile the Pattern instance from a stream.  The original pattern
1318      * string is read in and the object tree is recompiled from it.
1319      */
1320     private void readObject(java.io.ObjectInputStream s)
1321         throws java.io.IOException, ClassNotFoundException {
1322 
1323         // Read in all fields
1324         s.defaultReadObject();
1325 
1326         // Initialize counts
1327         capturingGroupCount = 1;
1328         localCount = 0;
1329 
1330         // if length > 0, the Pattern is lazily compiled
1331         compiled = false;
1332         if (pattern.length() == 0) {
1333             root = new Start(lastAccept);
1334             matchRoot = lastAccept;
1335             compiled = true;
1336         }
1337     }
1338 
1339     /**
1340      * This private constructor is used to create all Patterns. The pattern
1341      * string and match flags are all that is needed to completely describe
1342      * a Pattern. An empty pattern string results in an object tree with
1343      * only a Start node and a LastNode node.
1344      */
1345     private Pattern(String p, int f) {
1346         if ((f & ~ALL_FLAGS) != 0) {
1347             throw new IllegalArgumentException("Unknown flag 0x"
1348                                                + Integer.toHexString(f));
1349         }
1350         pattern = p;
1351         flags = f;
1352 
1353         // to use UNICODE_CASE if UNICODE_CHARACTER_CLASS present
1354         if ((flags & UNICODE_CHARACTER_CLASS) != 0)
1355             flags |= UNICODE_CASE;
1356 
1357         // Reset group index count
1358         capturingGroupCount = 1;
1359         localCount = 0;
1360 
1361         if (pattern.length() > 0) {
1362             compile();
1363         } else {
1364             root = new Start(lastAccept);
1365             matchRoot = lastAccept;
1366         }
1367     }
1368 
1369     /**
1370      * The pattern is converted to normalizedD form and then a pure group
1371      * is constructed to match canonical equivalences of the characters.
1372      */
1373     private void normalize() {
1374         boolean inCharClass = false;
1375         int lastCodePoint = -1;
1376 
1377         // Convert pattern into normalizedD form
1378         normalizedPattern = Normalizer.normalize(pattern, Normalizer.Form.NFD);
1379         patternLength = normalizedPattern.length();
1380 
1381         // Modify pattern to match canonical equivalences
1382         StringBuilder newPattern = new StringBuilder(patternLength);
1383         for(int i=0; i<patternLength; ) {
1384             int c = normalizedPattern.codePointAt(i);
1385             StringBuilder sequenceBuffer;
1386             if ((Character.getType(c) == Character.NON_SPACING_MARK)
1387                 && (lastCodePoint != -1)) {
1388                 sequenceBuffer = new StringBuilder();
1389                 sequenceBuffer.appendCodePoint(lastCodePoint);
1390                 sequenceBuffer.appendCodePoint(c);
1391                 while(Character.getType(c) == Character.NON_SPACING_MARK) {
1392                     i += Character.charCount(c);
1393                     if (i >= patternLength)
1394                         break;
1395                     c = normalizedPattern.codePointAt(i);
1396                     sequenceBuffer.appendCodePoint(c);
1397                 }
1398                 String ea = produceEquivalentAlternation(
1399                                                sequenceBuffer.toString());
1400                 newPattern.setLength(newPattern.length()-Character.charCount(lastCodePoint));
1401                 newPattern.append("(?:").append(ea).append(")");
1402             } else if (c == '[' && lastCodePoint != '\\') {
1403                 i = normalizeCharClass(newPattern, i);
1404             } else {
1405                 newPattern.appendCodePoint(c);
1406             }
1407             lastCodePoint = c;
1408             i += Character.charCount(c);
1409         }
1410         normalizedPattern = newPattern.toString();
1411     }
1412 
1413     /**
1414      * Complete the character class being parsed and add a set
1415      * of alternations to it that will match the canonical equivalences
1416      * of the characters within the class.
1417      */
1418     private int normalizeCharClass(StringBuilder newPattern, int i) {
1419         StringBuilder charClass = new StringBuilder();
1420         StringBuilder eq = null;
1421         int lastCodePoint = -1;
1422         String result;
1423 
1424         i++;
1425         charClass.append("[");
1426         while(true) {
1427             int c = normalizedPattern.codePointAt(i);
1428             StringBuilder sequenceBuffer;
1429 
1430             if (c == ']' && lastCodePoint != '\\') {
1431                 charClass.append((char)c);
1432                 break;
1433             } else if (Character.getType(c) == Character.NON_SPACING_MARK) {
1434                 sequenceBuffer = new StringBuilder();
1435                 sequenceBuffer.appendCodePoint(lastCodePoint);
1436                 while(Character.getType(c) == Character.NON_SPACING_MARK) {
1437                     sequenceBuffer.appendCodePoint(c);
1438                     i += Character.charCount(c);
1439                     if (i >= normalizedPattern.length())
1440                         break;
1441                     c = normalizedPattern.codePointAt(i);
1442                 }
1443                 String ea = produceEquivalentAlternation(
1444                                                   sequenceBuffer.toString());
1445 
1446                 charClass.setLength(charClass.length()-Character.charCount(lastCodePoint));
1447                 if (eq == null)
1448                     eq = new StringBuilder();
1449                 eq.append('|');
1450                 eq.append(ea);
1451             } else {
1452                 charClass.appendCodePoint(c);
1453                 i++;
1454             }
1455             if (i == normalizedPattern.length())
1456                 throw error("Unclosed character class");
1457             lastCodePoint = c;
1458         }
1459 
1460         if (eq != null) {
1461             result = "(?:"+charClass.toString()+eq.toString()+")";
1462         } else {
1463             result = charClass.toString();
1464         }
1465 
1466         newPattern.append(result);
1467         return i;
1468     }
1469 
1470     /**
1471      * Given a specific sequence composed of a regular character and
1472      * combining marks that follow it, produce the alternation that will
1473      * match all canonical equivalences of that sequence.
1474      */
1475     private String produceEquivalentAlternation(String source) {
1476         int len = countChars(source, 0, 1);
1477         if (source.length() == len)
1478             // source has one character.
1479             return source;
1480 
1481         String base = source.substring(0,len);
1482         String combiningMarks = source.substring(len);
1483 
1484         String[] perms = producePermutations(combiningMarks);
1485         StringBuilder result = new StringBuilder(source);
1486 
1487         // Add combined permutations
1488         for(int x=0; x<perms.length; x++) {
1489             String next = base + perms[x];
1490             if (x>0)
1491                 result.append("|"+next);
1492             next = composeOneStep(next);
1493             if (next != null)
1494                 result.append("|"+produceEquivalentAlternation(next));
1495         }
1496         return result.toString();
1497     }
1498 
1499     /**
1500      * Returns an array of strings that have all the possible
1501      * permutations of the characters in the input string.
1502      * This is used to get a list of all possible orderings
1503      * of a set of combining marks. Note that some of the permutations
1504      * are invalid because of combining class collisions, and these
1505      * possibilities must be removed because they are not canonically
1506      * equivalent.
1507      */
1508     private String[] producePermutations(String input) {
1509         if (input.length() == countChars(input, 0, 1))
1510             return new String[] {input};
1511 
1512         if (input.length() == countChars(input, 0, 2)) {
1513             int c0 = Character.codePointAt(input, 0);
1514             int c1 = Character.codePointAt(input, Character.charCount(c0));
1515             if (getClass(c1) == getClass(c0)) {
1516                 return new String[] {input};
1517             }
1518             String[] result = new String[2];
1519             result[0] = input;
1520             StringBuilder sb = new StringBuilder(2);
1521             sb.appendCodePoint(c1);
1522             sb.appendCodePoint(c0);
1523             result[1] = sb.toString();
1524             return result;
1525         }
1526 
1527         int length = 1;
1528         int nCodePoints = countCodePoints(input);
1529         for(int x=1; x<nCodePoints; x++)
1530             length = length * (x+1);
1531 
1532         String[] temp = new String[length];
1533 
1534         int combClass[] = new int[nCodePoints];
1535         for(int x=0, i=0; x<nCodePoints; x++) {
1536             int c = Character.codePointAt(input, i);
1537             combClass[x] = getClass(c);
1538             i +=  Character.charCount(c);
1539         }
1540 
1541         // For each char, take it out and add the permutations
1542         // of the remaining chars
1543         int index = 0;
1544         int len;
1545         // offset maintains the index in code units.
1546 loop:   for(int x=0, offset=0; x<nCodePoints; x++, offset+=len) {
1547             len = countChars(input, offset, 1);
1548             boolean skip = false;
1549             for(int y=x-1; y>=0; y--) {
1550                 if (combClass[y] == combClass[x]) {
1551                     continue loop;
1552                 }
1553             }
1554             StringBuilder sb = new StringBuilder(input);
1555             String otherChars = sb.delete(offset, offset+len).toString();
1556             String[] subResult = producePermutations(otherChars);
1557 
1558             String prefix = input.substring(offset, offset+len);
1559             for (String sre : subResult)
1560                 temp[index++] = prefix + sre;
1561         }
1562         String[] result = new String[index];
1563         for (int x=0; x<index; x++)
1564             result[x] = temp[x];
1565         return result;
1566     }
1567 
1568     private int getClass(int c) {
1569         return sun.text.Normalizer.getCombiningClass(c);
1570     }
1571 
1572     /**
1573      * Attempts to compose input by combining the first character
1574      * with the first combining mark following it. Returns a String
1575      * that is the composition of the leading character with its first
1576      * combining mark followed by the remaining combining marks. Returns
1577      * null if the first two characters cannot be further composed.
1578      */
1579     private String composeOneStep(String input) {
1580         int len = countChars(input, 0, 2);
1581         String firstTwoCharacters = input.substring(0, len);
1582         String result = Normalizer.normalize(firstTwoCharacters, Normalizer.Form.NFC);
1583 
1584         if (result.equals(firstTwoCharacters))
1585             return null;
1586         else {
1587             String remainder = input.substring(len);
1588             return result + remainder;
1589         }
1590     }
1591 
1592     /**
1593      * Preprocess any \Q...\E sequences in `temp', meta-quoting them.
1594      * See the description of `quotemeta' in perlfunc(1).
1595      */
1596     private void RemoveQEQuoting() {
1597         final int pLen = patternLength;
1598         int i = 0;
1599         while (i < pLen-1) {
1600             if (temp[i] != '\\')
1601                 i += 1;
1602             else if (temp[i + 1] != 'Q')
1603                 i += 2;
1604             else
1605                 break;
1606         }
1607         if (i >= pLen - 1)    // No \Q sequence found
1608             return;
1609         int j = i;
1610         i += 2;
1611         int[] newtemp = new int[j + 3*(pLen-i) + 2];
1612         System.arraycopy(temp, 0, newtemp, 0, j);
1613 
1614         boolean inQuote = true;
1615         boolean beginQuote = true;
1616         while (i < pLen) {
1617             int c = temp[i++];
1618             if (!ASCII.isAscii(c) || ASCII.isAlpha(c)) {
1619                 newtemp[j++] = c;
1620             } else if (ASCII.isDigit(c)) {
1621                 if (beginQuote) {
1622                     /*
1623                      * A unicode escape \[0xu] could be before this quote,
1624                      * and we don't want this numeric char to processed as
1625                      * part of the escape.
1626                      */
1627                     newtemp[j++] = '\\';
1628                     newtemp[j++] = 'x';
1629                     newtemp[j++] = '3';
1630                 }
1631                 newtemp[j++] = c;
1632             } else if (c != '\\') {
1633                 if (inQuote) newtemp[j++] = '\\';
1634                 newtemp[j++] = c;
1635             } else if (inQuote) {
1636                 if (temp[i] == 'E') {
1637                     i++;
1638                     inQuote = false;
1639                 } else {
1640                     newtemp[j++] = '\\';
1641                     newtemp[j++] = '\\';
1642                 }
1643             } else {
1644                 if (temp[i] == 'Q') {
1645                     i++;
1646                     inQuote = true;
1647                     beginQuote = true;
1648                     continue;
1649                 } else {
1650                     newtemp[j++] = c;
1651                     if (i != pLen)
1652                         newtemp[j++] = temp[i++];
1653                 }
1654             }
1655 
1656             beginQuote = false;
1657         }
1658 
1659         patternLength = j;
1660         temp = Arrays.copyOf(newtemp, j + 2); // double zero termination
1661     }
1662 
1663     /**
1664      * Copies regular expression to an int array and invokes the parsing
1665      * of the expression which will create the object tree.
1666      */
1667     private void compile() {
1668         // Handle canonical equivalences
1669         if (has(CANON_EQ) && !has(LITERAL)) {
1670             normalize();
1671         } else {
1672             normalizedPattern = pattern;
1673         }
1674         patternLength = normalizedPattern.length();
1675 
1676         // Copy pattern to int array for convenience
1677         // Use double zero to terminate pattern
1678         temp = new int[patternLength + 2];
1679 
1680         hasSupplementary = false;
1681         int c, count = 0;
1682         // Convert all chars into code points
1683         for (int x = 0; x < patternLength; x += Character.charCount(c)) {
1684             c = normalizedPattern.codePointAt(x);
1685             if (isSupplementary(c)) {
1686                 hasSupplementary = true;
1687             }
1688             temp[count++] = c;
1689         }
1690 
1691         patternLength = count;   // patternLength now in code points
1692 
1693         if (! has(LITERAL))
1694             RemoveQEQuoting();
1695 
1696         // Allocate all temporary objects here.
1697         buffer = new int[32];
1698         groupNodes = new GroupHead[10];
1699         namedGroups = null;
1700 
1701         if (has(LITERAL)) {
1702             // Literal pattern handling
1703             matchRoot = newSlice(temp, patternLength, hasSupplementary);
1704             matchRoot.next = lastAccept;
1705         } else {
1706             // Start recursive descent parsing
1707             matchRoot = expr(lastAccept);
1708             // Check extra pattern characters
1709             if (patternLength != cursor) {
1710                 if (peek() == ')') {
1711                     throw error("Unmatched closing ')'");
1712                 } else {
1713                     throw error("Unexpected internal error");
1714                 }
1715             }
1716         }
1717 
1718         // Peephole optimization
1719         if (matchRoot instanceof Slice) {
1720             root = BnM.optimize(matchRoot);
1721             if (root == matchRoot) {
1722                 root = hasSupplementary ? new StartS(matchRoot) : new Start(matchRoot);
1723             }
1724         } else if (matchRoot instanceof Begin || matchRoot instanceof First) {
1725             root = matchRoot;
1726         } else {
1727             root = hasSupplementary ? new StartS(matchRoot) : new Start(matchRoot);
1728         }
1729 
1730         // Release temporary storage
1731         temp = null;
1732         buffer = null;
1733         groupNodes = null;
1734         patternLength = 0;
1735         compiled = true;
1736     }
1737 
1738     Map<String, Integer> namedGroups() {
1739         if (namedGroups == null)
1740             namedGroups = new HashMap<>(2);
1741         return namedGroups;
1742     }
1743 
1744     /**
1745      * Used to print out a subtree of the Pattern to help with debugging.
1746      */
1747     private static void printObjectTree(Node node) {
1748         while(node != null) {
1749             if (node instanceof Prolog) {
1750                 System.out.println(node);
1751                 printObjectTree(((Prolog)node).loop);
1752                 System.out.println("**** end contents prolog loop");
1753             } else if (node instanceof Loop) {
1754                 System.out.println(node);
1755                 printObjectTree(((Loop)node).body);
1756                 System.out.println("**** end contents Loop body");
1757             } else if (node instanceof Curly) {
1758                 System.out.println(node);
1759                 printObjectTree(((Curly)node).atom);
1760                 System.out.println("**** end contents Curly body");
1761             } else if (node instanceof GroupCurly) {
1762                 System.out.println(node);
1763                 printObjectTree(((GroupCurly)node).atom);
1764                 System.out.println("**** end contents GroupCurly body");
1765             } else if (node instanceof GroupTail) {
1766                 System.out.println(node);
1767                 System.out.println("Tail next is "+node.next);
1768                 return;
1769             } else {
1770                 System.out.println(node);
1771             }
1772             node = node.next;
1773             if (node != null)
1774                 System.out.println("->next:");
1775             if (node == Pattern.accept) {
1776                 System.out.println("Accept Node");
1777                 node = null;
1778             }
1779        }
1780     }
1781 
1782     /**
1783      * Used to accumulate information about a subtree of the object graph
1784      * so that optimizations can be applied to the subtree.
1785      */
1786     static final class TreeInfo {
1787         int minLength;
1788         int maxLength;
1789         boolean maxValid;
1790         boolean deterministic;
1791 
1792         TreeInfo() {
1793             reset();
1794         }
1795         void reset() {
1796             minLength = 0;
1797             maxLength = 0;
1798             maxValid = true;
1799             deterministic = true;
1800         }
1801     }
1802 
1803     /*
1804      * The following private methods are mainly used to improve the
1805      * readability of the code. In order to let the Java compiler easily
1806      * inline them, we should not put many assertions or error checks in them.
1807      */
1808 
1809     /**
1810      * Indicates whether a particular flag is set or not.
1811      */
1812     private boolean has(int f) {
1813         return (flags & f) != 0;
1814     }
1815 
1816     /**
1817      * Match next character, signal error if failed.
1818      */
1819     private void accept(int ch, String s) {
1820         int testChar = temp[cursor++];
1821         if (has(COMMENTS))
1822             testChar = parsePastWhitespace(testChar);
1823         if (ch != testChar) {
1824             throw error(s);
1825         }
1826     }
1827 
1828     /**
1829      * Mark the end of pattern with a specific character.
1830      */
1831     private void mark(int c) {
1832         temp[patternLength] = c;
1833     }
1834 
1835     /**
1836      * Peek the next character, and do not advance the cursor.
1837      */
1838     private int peek() {
1839         int ch = temp[cursor];
1840         if (has(COMMENTS))
1841             ch = peekPastWhitespace(ch);
1842         return ch;
1843     }
1844 
1845     /**
1846      * Read the next character, and advance the cursor by one.
1847      */
1848     private int read() {
1849         int ch = temp[cursor++];
1850         if (has(COMMENTS))
1851             ch = parsePastWhitespace(ch);
1852         return ch;
1853     }
1854 
1855     /**
1856      * Read the next character, and advance the cursor by one,
1857      * ignoring the COMMENTS setting
1858      */
1859     private int readEscaped() {
1860         int ch = temp[cursor++];
1861         return ch;
1862     }
1863 
1864     /**
1865      * Advance the cursor by one, and peek the next character.
1866      */
1867     private int next() {
1868         int ch = temp[++cursor];
1869         if (has(COMMENTS))
1870             ch = peekPastWhitespace(ch);
1871         return ch;
1872     }
1873 
1874     /**
1875      * Advance the cursor by one, and peek the next character,
1876      * ignoring the COMMENTS setting
1877      */
1878     private int nextEscaped() {
1879         int ch = temp[++cursor];
1880         return ch;
1881     }
1882 
1883     /**
1884      * If in xmode peek past whitespace and comments.
1885      */
1886     private int peekPastWhitespace(int ch) {
1887         while (ASCII.isSpace(ch) || ch == '#') {
1888             while (ASCII.isSpace(ch))
1889                 ch = temp[++cursor];
1890             if (ch == '#') {
1891                 ch = peekPastLine();
1892             }
1893         }
1894         return ch;
1895     }
1896 
1897     /**
1898      * If in xmode parse past whitespace and comments.
1899      */
1900     private int parsePastWhitespace(int ch) {
1901         while (ASCII.isSpace(ch) || ch == '#') {
1902             while (ASCII.isSpace(ch))
1903                 ch = temp[cursor++];
1904             if (ch == '#')
1905                 ch = parsePastLine();
1906         }
1907         return ch;
1908     }
1909 
1910     /**
1911      * xmode parse past comment to end of line.
1912      */
1913     private int parsePastLine() {
1914         int ch = temp[cursor++];
1915         while (ch != 0 && !isLineSeparator(ch))
1916             ch = temp[cursor++];
1917         return ch;
1918     }
1919 
1920     /**
1921      * xmode peek past comment to end of line.
1922      */
1923     private int peekPastLine() {
1924         int ch = temp[++cursor];
1925         while (ch != 0 && !isLineSeparator(ch))
1926             ch = temp[++cursor];
1927         return ch;
1928     }
1929 
1930     /**
1931      * Determines if character is a line separator in the current mode
1932      */
1933     private boolean isLineSeparator(int ch) {
1934         if (has(UNIX_LINES)) {
1935             return ch == '\n';
1936         } else {
1937             return (ch == '\n' ||
1938                     ch == '\r' ||
1939                     (ch|1) == '\u2029' ||
1940                     ch == '\u0085');
1941         }
1942     }
1943 
1944     /**
1945      * Read the character after the next one, and advance the cursor by two.
1946      */
1947     private int skip() {
1948         int i = cursor;
1949         int ch = temp[i+1];
1950         cursor = i + 2;
1951         return ch;
1952     }
1953 
1954     /**
1955      * Unread one next character, and retreat cursor by one.
1956      */
1957     private void unread() {
1958         cursor--;
1959     }
1960 
1961     /**
1962      * Internal method used for handling all syntax errors. The pattern is
1963      * displayed with a pointer to aid in locating the syntax error.
1964      */
1965     private PatternSyntaxException error(String s) {
1966         return new PatternSyntaxException(s, normalizedPattern,  cursor - 1);
1967     }
1968 
1969     /**
1970      * Determines if there is any supplementary character or unpaired
1971      * surrogate in the specified range.
1972      */
1973     private boolean findSupplementary(int start, int end) {
1974         for (int i = start; i < end; i++) {
1975             if (isSupplementary(temp[i]))
1976                 return true;
1977         }
1978         return false;
1979     }
1980 
1981     /**
1982      * Determines if the specified code point is a supplementary
1983      * character or unpaired surrogate.
1984      */
1985     private static final boolean isSupplementary(int ch) {
1986         return ch >= Character.MIN_SUPPLEMENTARY_CODE_POINT ||
1987                Character.isSurrogate((char)ch);
1988     }
1989 
1990     /**
1991      *  The following methods handle the main parsing. They are sorted
1992      *  according to their precedence order, the lowest one first.
1993      */
1994 
1995     /**
1996      * The expression is parsed with branch nodes added for alternations.
1997      * This may be called recursively to parse sub expressions that may
1998      * contain alternations.
1999      */
2000     private Node expr(Node end) {
2001         Node prev = null;
2002         Node firstTail = null;
2003         Branch branch = null;
2004         Node branchConn = null;
2005 
2006         for (;;) {
2007             Node node = sequence(end);
2008             Node nodeTail = root;      //double return
2009             if (prev == null) {
2010                 prev = node;
2011                 firstTail = nodeTail;
2012             } else {
2013                 // Branch
2014                 if (branchConn == null) {
2015                     branchConn = new BranchConn();
2016                     branchConn.next = end;
2017                 }
2018                 if (node == end) {
2019                     // if the node returned from sequence() is "end"
2020                     // we have an empty expr, set a null atom into
2021                     // the branch to indicate to go "next" directly.
2022                     node = null;
2023                 } else {
2024                     // the "tail.next" of each atom goes to branchConn
2025                     nodeTail.next = branchConn;
2026                 }
2027                 if (prev == branch) {
2028                     branch.add(node);
2029                 } else {
2030                     if (prev == end) {
2031                         prev = null;
2032                     } else {
2033                         // replace the "end" with "branchConn" at its tail.next
2034                         // when put the "prev" into the branch as the first atom.
2035                         firstTail.next = branchConn;
2036                     }
2037                     prev = branch = new Branch(prev, node, branchConn);
2038                 }
2039             }
2040             if (peek() != '|') {
2041                 return prev;
2042             }
2043             next();
2044         }
2045     }
2046 
2047     @SuppressWarnings("fallthrough")
2048     /**
2049      * Parsing of sequences between alternations.
2050      */
2051     private Node sequence(Node end) {
2052         Node head = null;
2053         Node tail = null;
2054         Node node = null;
2055     LOOP:
2056         for (;;) {
2057             int ch = peek();
2058             switch (ch) {
2059             case '(':
2060                 // Because group handles its own closure,
2061                 // we need to treat it differently
2062                 node = group0();
2063                 // Check for comment or flag group
2064                 if (node == null)
2065                     continue;
2066                 if (head == null)
2067                     head = node;
2068                 else
2069                     tail.next = node;
2070                 // Double return: Tail was returned in root
2071                 tail = root;
2072                 continue;
2073             case '[':
2074                 node = clazz(true);
2075                 break;
2076             case '\\':
2077                 ch = nextEscaped();
2078                 if (ch == 'p' || ch == 'P') {
2079                     boolean oneLetter = true;
2080                     boolean comp = (ch == 'P');
2081                     ch = next(); // Consume { if present
2082                     if (ch != '{') {
2083                         unread();
2084                     } else {
2085                         oneLetter = false;
2086                     }
2087                     node = family(oneLetter, comp);
2088                 } else {
2089                     unread();
2090                     node = atom();
2091                 }
2092                 break;
2093             case '^':
2094                 next();
2095                 if (has(MULTILINE)) {
2096                     if (has(UNIX_LINES))
2097                         node = new UnixCaret();
2098                     else
2099                         node = new Caret();
2100                 } else {
2101                     node = new Begin();
2102                 }
2103                 break;
2104             case '$':
2105                 next();
2106                 if (has(UNIX_LINES))
2107                     node = new UnixDollar(has(MULTILINE));
2108                 else
2109                     node = new Dollar(has(MULTILINE));
2110                 break;
2111             case '.':
2112                 next();
2113                 if (has(DOTALL)) {
2114                     node = new All();
2115                 } else {
2116                     if (has(UNIX_LINES))
2117                         node = new UnixDot();
2118                     else {
2119                         node = new Dot();
2120                     }
2121                 }
2122                 break;
2123             case '|':
2124             case ')':
2125                 break LOOP;
2126             case ']': // Now interpreting dangling ] and } as literals
2127             case '}':
2128                 node = atom();
2129                 break;
2130             case '?':
2131             case '*':
2132             case '+':
2133                 next();
2134                 throw error("Dangling meta character '" + ((char)ch) + "'");
2135             case 0:
2136                 if (cursor >= patternLength) {
2137                     break LOOP;
2138                 }
2139                 // Fall through
2140             default:
2141                 node = atom();
2142                 break;
2143             }
2144 
2145             node = closure(node);
2146 
2147             if (head == null) {
2148                 head = tail = node;
2149             } else {
2150                 tail.next = node;
2151                 tail = node;
2152             }
2153         }
2154         if (head == null) {
2155             return end;
2156         }
2157         tail.next = end;
2158         root = tail;      //double return
2159         return head;
2160     }
2161 
2162     @SuppressWarnings("fallthrough")
2163     /**
2164      * Parse and add a new Single or Slice.
2165      */
2166     private Node atom() {
2167         int first = 0;
2168         int prev = -1;
2169         boolean hasSupplementary = false;
2170         int ch = peek();
2171         for (;;) {
2172             switch (ch) {
2173             case '*':
2174             case '+':
2175             case '?':
2176             case '{':
2177                 if (first > 1) {
2178                     cursor = prev;    // Unwind one character
2179                     first--;
2180                 }
2181                 break;
2182             case '$':
2183             case '.':
2184             case '^':
2185             case '(':
2186             case '[':
2187             case '|':
2188             case ')':
2189                 break;
2190             case '\\':
2191                 ch = nextEscaped();
2192                 if (ch == 'p' || ch == 'P') { // Property
2193                     if (first > 0) { // Slice is waiting; handle it first
2194                         unread();
2195                         break;
2196                     } else { // No slice; just return the family node
2197                         boolean comp = (ch == 'P');
2198                         boolean oneLetter = true;
2199                         ch = next(); // Consume { if present
2200                         if (ch != '{')
2201                             unread();
2202                         else
2203                             oneLetter = false;
2204                         return family(oneLetter, comp);
2205                     }
2206                 }
2207                 unread();
2208                 prev = cursor;
2209                 ch = escape(false, first == 0, false);
2210                 if (ch >= 0) {
2211                     append(ch, first);
2212                     first++;
2213                     if (isSupplementary(ch)) {
2214                         hasSupplementary = true;
2215                     }
2216                     ch = peek();
2217                     continue;
2218                 } else if (first == 0) {
2219                     return root;
2220                 }
2221                 // Unwind meta escape sequence
2222                 cursor = prev;
2223                 break;
2224             case 0:
2225                 if (cursor >= patternLength) {
2226                     break;
2227                 }
2228                 // Fall through
2229             default:
2230                 prev = cursor;
2231                 append(ch, first);
2232                 first++;
2233                 if (isSupplementary(ch)) {
2234                     hasSupplementary = true;
2235                 }
2236                 ch = next();
2237                 continue;
2238             }
2239             break;
2240         }
2241         if (first == 1) {
2242             return newSingle(buffer[0]);
2243         } else {
2244             return newSlice(buffer, first, hasSupplementary);
2245         }
2246     }
2247 
2248     private void append(int ch, int len) {
2249         if (len >= buffer.length) {
2250             int[] tmp = new int[len+len];
2251             System.arraycopy(buffer, 0, tmp, 0, len);
2252             buffer = tmp;
2253         }
2254         buffer[len] = ch;
2255     }
2256 
2257     /**
2258      * Parses a backref greedily, taking as many numbers as it
2259      * can. The first digit is always treated as a backref, but
2260      * multi digit numbers are only treated as a backref if at
2261      * least that many backrefs exist at this point in the regex.
2262      */
2263     private Node ref(int refNum) {
2264         boolean done = false;
2265         while(!done) {
2266             int ch = peek();
2267             switch(ch) {
2268             case '0':
2269             case '1':
2270             case '2':
2271             case '3':
2272             case '4':
2273             case '5':
2274             case '6':
2275             case '7':
2276             case '8':
2277             case '9':
2278                 int newRefNum = (refNum * 10) + (ch - '0');
2279                 // Add another number if it doesn't make a group
2280                 // that doesn't exist
2281                 if (capturingGroupCount - 1 < newRefNum) {
2282                     done = true;
2283                     break;
2284                 }
2285                 refNum = newRefNum;
2286                 read();
2287                 break;
2288             default:
2289                 done = true;
2290                 break;
2291             }
2292         }
2293         if (has(CASE_INSENSITIVE))
2294             return new CIBackRef(refNum, has(UNICODE_CASE));
2295         else
2296             return new BackRef(refNum);
2297     }
2298 
2299     /**
2300      * Parses an escape sequence to determine the actual value that needs
2301      * to be matched.
2302      * If -1 is returned and create was true a new object was added to the tree
2303      * to handle the escape sequence.
2304      * If the returned value is greater than zero, it is the value that
2305      * matches the escape sequence.
2306      */
2307     private int escape(boolean inclass, boolean create, boolean isrange) {
2308         int ch = skip();
2309         switch (ch) {
2310         case '0':
2311             return o();
2312         case '1':
2313         case '2':
2314         case '3':
2315         case '4':
2316         case '5':
2317         case '6':
2318         case '7':
2319         case '8':
2320         case '9':
2321             if (inclass) break;
2322             if (create) {
2323                 root = ref((ch - '0'));
2324             }
2325             return -1;
2326         case 'A':
2327             if (inclass) break;
2328             if (create) root = new Begin();
2329             return -1;
2330         case 'B':
2331             if (inclass) break;
2332             if (create) root = new Bound(Bound.NONE, has(UNICODE_CHARACTER_CLASS));
2333             return -1;
2334         case 'C':
2335             break;
2336         case 'D':
2337             if (create) root = has(UNICODE_CHARACTER_CLASS)
2338                                ? new Utype(UnicodeProp.DIGIT).complement()
2339                                : new Ctype(ASCII.DIGIT).complement();
2340             return -1;
2341         case 'E':
2342         case 'F':
2343             break;
2344         case 'G':
2345             if (inclass) break;
2346             if (create) root = new LastMatch();
2347             return -1;
2348         case 'H':
2349             if (create) root = new HorizWS().complement();
2350             return -1;
2351         case 'I':
2352         case 'J':
2353         case 'K':
2354         case 'L':
2355         case 'M':
2356         case 'N':
2357         case 'O':
2358         case 'P':
2359         case 'Q':
2360             break;
2361         case 'R':
2362             if (inclass) break;
2363             if (create) root = new LineEnding();
2364             return -1;
2365         case 'S':
2366             if (create) root = has(UNICODE_CHARACTER_CLASS)
2367                                ? new Utype(UnicodeProp.WHITE_SPACE).complement()
2368                                : new Ctype(ASCII.SPACE).complement();
2369             return -1;
2370         case 'T':
2371         case 'U':
2372             break;
2373         case 'V':
2374             if (create) root = new VertWS().complement();
2375             return -1;
2376         case 'W':
2377             if (create) root = has(UNICODE_CHARACTER_CLASS)
2378                                ? new Utype(UnicodeProp.WORD).complement()
2379                                : new Ctype(ASCII.WORD).complement();
2380             return -1;
2381         case 'X':
2382         case 'Y':
2383             break;
2384         case 'Z':
2385             if (inclass) break;
2386             if (create) {
2387                 if (has(UNIX_LINES))
2388                     root = new UnixDollar(false);
2389                 else
2390                     root = new Dollar(false);
2391             }
2392             return -1;
2393         case 'a':
2394             return '\007';
2395         case 'b':
2396             if (inclass) break;
2397             if (create) root = new Bound(Bound.BOTH, has(UNICODE_CHARACTER_CLASS));
2398             return -1;
2399         case 'c':
2400             return c();
2401         case 'd':
2402             if (create) root = has(UNICODE_CHARACTER_CLASS)
2403                                ? new Utype(UnicodeProp.DIGIT)
2404                                : new Ctype(ASCII.DIGIT);
2405             return -1;
2406         case 'e':
2407             return '\033';
2408         case 'f':
2409             return '\f';
2410         case 'g':
2411             break;
2412         case 'h':
2413             if (create) root = new HorizWS();
2414             return -1;
2415         case 'i':
2416         case 'j':
2417             break;
2418         case 'k':
2419             if (inclass)
2420                 break;
2421             if (read() != '<')
2422                 throw error("\\k is not followed by '<' for named capturing group");
2423             String name = groupname(read());
2424             if (!namedGroups().containsKey(name))
2425                 throw error("(named capturing group <"+ name+"> does not exit");
2426             if (create) {
2427                 if (has(CASE_INSENSITIVE))
2428                     root = new CIBackRef(namedGroups().get(name), has(UNICODE_CASE));
2429                 else
2430                     root = new BackRef(namedGroups().get(name));
2431             }
2432             return -1;
2433         case 'l':
2434         case 'm':
2435             break;
2436         case 'n':
2437             return '\n';
2438         case 'o':
2439         case 'p':
2440         case 'q':
2441             break;
2442         case 'r':
2443             return '\r';
2444         case 's':
2445             if (create) root = has(UNICODE_CHARACTER_CLASS)
2446                                ? new Utype(UnicodeProp.WHITE_SPACE)
2447                                : new Ctype(ASCII.SPACE);
2448             return -1;
2449         case 't':
2450             return '\t';
2451         case 'u':
2452             return u();
2453         case 'v':
2454             // '\v' was implemented as VT/0x0B in releases < 1.8 (though
2455             // undocumented). In JDK8 '\v' is specified as a predefined
2456             // character class for all vertical whitespace characters.
2457             // So [-1, root=VertWS node] pair is returned (instead of a
2458             // single 0x0B). This breaks the range if '\v' is used as
2459             // the start or end value, such as [\v-...] or [...-\v], in
2460             // which a single definite value (0x0B) is expected. For
2461             // compatibility concern '\013'/0x0B is returned if isrange.
2462             if (isrange)
2463                 return '\013';
2464             if (create) root = new VertWS();
2465             return -1;
2466         case 'w':
2467             if (create) root = has(UNICODE_CHARACTER_CLASS)
2468                                ? new Utype(UnicodeProp.WORD)
2469                                : new Ctype(ASCII.WORD);
2470             return -1;
2471         case 'x':
2472             return x();
2473         case 'y':
2474             break;
2475         case 'z':
2476             if (inclass) break;
2477             if (create) root = new End();
2478             return -1;
2479         default:
2480             return ch;
2481         }
2482         throw error("Illegal/unsupported escape sequence");
2483     }
2484 
2485     /**
2486      * Parse a character class, and return the node that matches it.
2487      *
2488      * Consumes a ] on the way out if consume is true. Usually consume
2489      * is true except for the case of [abc&&def] where def is a separate
2490      * right hand node with "understood" brackets.
2491      */
2492     private CharProperty clazz(boolean consume) {
2493         CharProperty prev = null;
2494         CharProperty node = null;
2495         BitClass bits = new BitClass();
2496         boolean include = true;
2497         boolean firstInClass = true;
2498         int ch = next();
2499         for (;;) {
2500             switch (ch) {
2501                 case '^':
2502                     // Negates if first char in a class, otherwise literal
2503                     if (firstInClass) {
2504                         if (temp[cursor-1] != '[')
2505                             break;
2506                         ch = next();
2507                         include = !include;
2508                         continue;
2509                     } else {
2510                         // ^ not first in class, treat as literal
2511                         break;
2512                     }
2513                 case '[':
2514                     firstInClass = false;
2515                     node = clazz(true);
2516                     if (prev == null)
2517                         prev = node;
2518                     else
2519                         prev = union(prev, node);
2520                     ch = peek();
2521                     continue;
2522                 case '&':
2523                     firstInClass = false;
2524                     ch = next();
2525                     if (ch == '&') {
2526                         ch = next();
2527                         CharProperty rightNode = null;
2528                         while (ch != ']' && ch != '&') {
2529                             if (ch == '[') {
2530                                 if (rightNode == null)
2531                                     rightNode = clazz(true);
2532                                 else
2533                                     rightNode = union(rightNode, clazz(true));
2534                             } else { // abc&&def
2535                                 unread();
2536                                 rightNode = clazz(false);
2537                             }
2538                             ch = peek();
2539                         }
2540                         if (rightNode != null)
2541                             node = rightNode;
2542                         if (prev == null) {
2543                             if (rightNode == null)
2544                                 throw error("Bad class syntax");
2545                             else
2546                                 prev = rightNode;
2547                         } else {
2548                             prev = intersection(prev, node);
2549                         }
2550                     } else {
2551                         // treat as a literal &
2552                         unread();
2553                         break;
2554                     }
2555                     continue;
2556                 case 0:
2557                     firstInClass = false;
2558                     if (cursor >= patternLength)
2559                         throw error("Unclosed character class");
2560                     break;
2561                 case ']':
2562                     firstInClass = false;
2563                     if (prev != null) {
2564                         if (consume)
2565                             next();
2566                         return prev;
2567                     }
2568                     break;
2569                 default:
2570                     firstInClass = false;
2571                     break;
2572             }
2573             node = range(bits);
2574             if (include) {
2575                 if (prev == null) {
2576                     prev = node;
2577                 } else {
2578                     if (prev != node)
2579                         prev = union(prev, node);
2580                 }
2581             } else {
2582                 if (prev == null) {
2583                     prev = node.complement();
2584                 } else {
2585                     if (prev != node)
2586                         prev = setDifference(prev, node);
2587                 }
2588             }
2589             ch = peek();
2590         }
2591     }
2592 
2593     private CharProperty bitsOrSingle(BitClass bits, int ch) {
2594         /* Bits can only handle codepoints in [u+0000-u+00ff] range.
2595            Use "single" node instead of bits when dealing with unicode
2596            case folding for codepoints listed below.
2597            (1)Uppercase out of range: u+00ff, u+00b5
2598               toUpperCase(u+00ff) -> u+0178
2599               toUpperCase(u+00b5) -> u+039c
2600            (2)LatinSmallLetterLongS u+17f
2601               toUpperCase(u+017f) -> u+0053
2602            (3)LatinSmallLetterDotlessI u+131
2603               toUpperCase(u+0131) -> u+0049
2604            (4)LatinCapitalLetterIWithDotAbove u+0130
2605               toLowerCase(u+0130) -> u+0069
2606            (5)KelvinSign u+212a
2607               toLowerCase(u+212a) ==> u+006B
2608            (6)AngstromSign u+212b
2609               toLowerCase(u+212b) ==> u+00e5
2610         */
2611         int d;
2612         if (ch < 256 &&
2613             !(has(CASE_INSENSITIVE) && has(UNICODE_CASE) &&
2614               (ch == 0xff || ch == 0xb5 ||
2615                ch == 0x49 || ch == 0x69 ||  //I and i
2616                ch == 0x53 || ch == 0x73 ||  //S and s
2617                ch == 0x4b || ch == 0x6b ||  //K and k
2618                ch == 0xc5 || ch == 0xe5)))  //A+ring
2619             return bits.add(ch, flags());
2620         return newSingle(ch);
2621     }
2622 
2623     /**
2624      * Parse a single character or a character range in a character class
2625      * and return its representative node.
2626      */
2627     private CharProperty range(BitClass bits) {
2628         int ch = peek();
2629         if (ch == '\\') {
2630             ch = nextEscaped();
2631             if (ch == 'p' || ch == 'P') { // A property
2632                 boolean comp = (ch == 'P');
2633                 boolean oneLetter = true;
2634                 // Consume { if present
2635                 ch = next();
2636                 if (ch != '{')
2637                     unread();
2638                 else
2639                     oneLetter = false;
2640                 return family(oneLetter, comp);
2641             } else { // ordinary escape
2642                 boolean isrange = temp[cursor+1] == '-';
2643                 unread();
2644                 ch = escape(true, true, isrange);
2645                 if (ch == -1)
2646                     return (CharProperty) root;
2647             }
2648         } else {
2649             next();
2650         }
2651         if (ch >= 0) {
2652             if (peek() == '-') {
2653                 int endRange = temp[cursor+1];
2654                 if (endRange == '[') {
2655                     return bitsOrSingle(bits, ch);
2656                 }
2657                 if (endRange != ']') {
2658                     next();
2659                     int m = peek();
2660                     if (m == '\\') {
2661                         m = escape(true, false, true);
2662                     } else {
2663                         next();
2664                     }
2665                     if (m < ch) {
2666                         throw error("Illegal character range");
2667                     }
2668                     if (has(CASE_INSENSITIVE))
2669                         return caseInsensitiveRangeFor(ch, m);
2670                     else
2671                         return rangeFor(ch, m);
2672                 }
2673             }
2674             return bitsOrSingle(bits, ch);
2675         }
2676         throw error("Unexpected character '"+((char)ch)+"'");
2677     }
2678 
2679     /**
2680      * Parses a Unicode character family and returns its representative node.
2681      */
2682     private CharProperty family(boolean singleLetter,
2683                                 boolean maybeComplement)
2684     {
2685         next();
2686         String name;
2687         CharProperty node = null;
2688 
2689         if (singleLetter) {
2690             int c = temp[cursor];
2691             if (!Character.isSupplementaryCodePoint(c)) {
2692                 name = String.valueOf((char)c);
2693             } else {
2694                 name = new String(temp, cursor, 1);
2695             }
2696             read();
2697         } else {
2698             int i = cursor;
2699             mark('}');
2700             while(read() != '}') {
2701             }
2702             mark('\000');
2703             int j = cursor;
2704             if (j > patternLength)
2705                 throw error("Unclosed character family");
2706             if (i + 1 >= j)
2707                 throw error("Empty character family");
2708             name = new String(temp, i, j-i-1);
2709         }
2710 
2711         int i = name.indexOf('=');
2712         if (i != -1) {
2713             // property construct \p{name=value}
2714             String value = name.substring(i + 1);
2715             name = name.substring(0, i).toLowerCase(Locale.ENGLISH);
2716             switch (name) {
2717                 case "sc":
2718                 case "script":
2719                     node = unicodeScriptPropertyFor(value);
2720                     break;
2721                 case "blk":
2722                 case "block":
2723                     node = unicodeBlockPropertyFor(value);
2724                     break;
2725                 case "gc":
2726                 case "general_category":
2727                     node = charPropertyNodeFor(value);
2728                     break;
2729                 default:
2730                     throw error("Unknown Unicode property {name=<" + name + ">, "
2731                                 + "value=<" + value + ">}");
2732             }
2733         } else {
2734             if (name.startsWith("In")) {
2735                 // \p{inBlockName}
2736                 node = unicodeBlockPropertyFor(name.substring(2));
2737             } else if (name.startsWith("Is")) {
2738                 // \p{isGeneralCategory} and \p{isScriptName}
2739                 name = name.substring(2);
2740                 UnicodeProp uprop = UnicodeProp.forName(name);
2741                 if (uprop != null)
2742                     node = new Utype(uprop);
2743                 if (node == null)
2744                     node = CharPropertyNames.charPropertyFor(name);
2745                 if (node == null)
2746                     node = unicodeScriptPropertyFor(name);
2747             } else {
2748                 if (has(UNICODE_CHARACTER_CLASS)) {
2749                     UnicodeProp uprop = UnicodeProp.forPOSIXName(name);
2750                     if (uprop != null)
2751                         node = new Utype(uprop);
2752                 }
2753                 if (node == null)
2754                     node = charPropertyNodeFor(name);
2755             }
2756         }
2757         if (maybeComplement) {
2758             if (node instanceof Category || node instanceof Block)
2759                 hasSupplementary = true;
2760             node = node.complement();
2761         }
2762         return node;
2763     }
2764 
2765 
2766     /**
2767      * Returns a CharProperty matching all characters belong to
2768      * a UnicodeScript.
2769      */
2770     private CharProperty unicodeScriptPropertyFor(String name) {
2771         final Character.UnicodeScript script;
2772         try {
2773             script = Character.UnicodeScript.forName(name);
2774         } catch (IllegalArgumentException iae) {
2775             throw error("Unknown character script name {" + name + "}");
2776         }
2777         return new Script(script);
2778     }
2779 
2780     /**
2781      * Returns a CharProperty matching all characters in a UnicodeBlock.
2782      */
2783     private CharProperty unicodeBlockPropertyFor(String name) {
2784         final Character.UnicodeBlock block;
2785         try {
2786             block = Character.UnicodeBlock.forName(name);
2787         } catch (IllegalArgumentException iae) {
2788             throw error("Unknown character block name {" + name + "}");
2789         }
2790         return new Block(block);
2791     }
2792 
2793     /**
2794      * Returns a CharProperty matching all characters in a named property.
2795      */
2796     private CharProperty charPropertyNodeFor(String name) {
2797         CharProperty p = CharPropertyNames.charPropertyFor(name);
2798         if (p == null)
2799             throw error("Unknown character property name {" + name + "}");
2800         return p;
2801     }
2802 
2803     /**
2804      * Parses and returns the name of a "named capturing group", the trailing
2805      * ">" is consumed after parsing.
2806      */
2807     private String groupname(int ch) {
2808         StringBuilder sb = new StringBuilder();
2809         sb.append(Character.toChars(ch));
2810         while (ASCII.isLower(ch=read()) || ASCII.isUpper(ch) ||
2811                ASCII.isDigit(ch)) {
2812             sb.append(Character.toChars(ch));
2813         }
2814         if (sb.length() == 0)
2815             throw error("named capturing group has 0 length name");
2816         if (ch != '>')
2817             throw error("named capturing group is missing trailing '>'");
2818         return sb.toString();
2819     }
2820 
2821     /**
2822      * Parses a group and returns the head node of a set of nodes that process
2823      * the group. Sometimes a double return system is used where the tail is
2824      * returned in root.
2825      */
2826     private Node group0() {
2827         boolean capturingGroup = false;
2828         Node head = null;
2829         Node tail = null;
2830         int save = flags;
2831         root = null;
2832         int ch = next();
2833         if (ch == '?') {
2834             ch = skip();
2835             switch (ch) {
2836             case ':':   //  (?:xxx) pure group
2837                 head = createGroup(true);
2838                 tail = root;
2839                 head.next = expr(tail);
2840                 break;
2841             case '=':   // (?=xxx) and (?!xxx) lookahead
2842             case '!':
2843                 head = createGroup(true);
2844                 tail = root;
2845                 head.next = expr(tail);
2846                 if (ch == '=') {
2847                     head = tail = new Pos(head);
2848                 } else {
2849                     head = tail = new Neg(head);
2850                 }
2851                 break;
2852             case '>':   // (?>xxx)  independent group
2853                 head = createGroup(true);
2854                 tail = root;
2855                 head.next = expr(tail);
2856                 head = tail = new Ques(head, INDEPENDENT);
2857                 break;
2858             case '<':   // (?<xxx)  look behind
2859                 ch = read();
2860                 if (ASCII.isLower(ch) || ASCII.isUpper(ch)) {
2861                     // named captured group
2862                     String name = groupname(ch);
2863                     if (namedGroups().containsKey(name))
2864                         throw error("Named capturing group <" + name
2865                                     + "> is already defined");
2866                     capturingGroup = true;
2867                     head = createGroup(false);
2868                     tail = root;
2869                     namedGroups().put(name, capturingGroupCount-1);
2870                     head.next = expr(tail);
2871                     break;
2872                 }
2873                 int start = cursor;
2874                 head = createGroup(true);
2875                 tail = root;
2876                 head.next = expr(tail);
2877                 tail.next = lookbehindEnd;
2878                 TreeInfo info = new TreeInfo();
2879                 head.study(info);
2880                 if (info.maxValid == false) {
2881                     throw error("Look-behind group does not have "
2882                                 + "an obvious maximum length");
2883                 }
2884                 boolean hasSupplementary = findSupplementary(start, patternLength);
2885                 if (ch == '=') {
2886                     head = tail = (hasSupplementary ?
2887                                    new BehindS(head, info.maxLength,
2888                                                info.minLength) :
2889                                    new Behind(head, info.maxLength,
2890                                               info.minLength));
2891                 } else if (ch == '!') {
2892                     head = tail = (hasSupplementary ?
2893                                    new NotBehindS(head, info.maxLength,
2894                                                   info.minLength) :
2895                                    new NotBehind(head, info.maxLength,
2896                                                  info.minLength));
2897                 } else {
2898                     throw error("Unknown look-behind group");
2899                 }
2900                 break;
2901             case '$':
2902             case '@':
2903                 throw error("Unknown group type");
2904             default:    // (?xxx:) inlined match flags
2905                 unread();
2906                 addFlag();
2907                 ch = read();
2908                 if (ch == ')') {
2909                     return null;    // Inline modifier only
2910                 }
2911                 if (ch != ':') {
2912                     throw error("Unknown inline modifier");
2913                 }
2914                 head = createGroup(true);
2915                 tail = root;
2916                 head.next = expr(tail);
2917                 break;
2918             }
2919         } else { // (xxx) a regular group
2920             capturingGroup = true;
2921             head = createGroup(false);
2922             tail = root;
2923             head.next = expr(tail);
2924         }
2925 
2926         accept(')', "Unclosed group");
2927         flags = save;
2928 
2929         // Check for quantifiers
2930         Node node = closure(head);
2931         if (node == head) { // No closure
2932             root = tail;
2933             return node;    // Dual return
2934         }
2935         if (head == tail) { // Zero length assertion
2936             root = node;
2937             return node;    // Dual return
2938         }
2939 
2940         if (node instanceof Ques) {
2941             Ques ques = (Ques) node;
2942             if (ques.type == POSSESSIVE) {
2943                 root = node;
2944                 return node;
2945             }
2946             tail.next = new BranchConn();
2947             tail = tail.next;
2948             if (ques.type == GREEDY) {
2949                 head = new Branch(head, null, tail);
2950             } else { // Reluctant quantifier
2951                 head = new Branch(null, head, tail);
2952             }
2953             root = tail;
2954             return head;
2955         } else if (node instanceof Curly) {
2956             Curly curly = (Curly) node;
2957             if (curly.type == POSSESSIVE) {
2958                 root = node;
2959                 return node;
2960             }
2961             // Discover if the group is deterministic
2962             TreeInfo info = new TreeInfo();
2963             if (head.study(info)) { // Deterministic
2964                 GroupTail temp = (GroupTail) tail;
2965                 head = root = new GroupCurly(head.next, curly.cmin,
2966                                    curly.cmax, curly.type,
2967                                    ((GroupTail)tail).localIndex,
2968                                    ((GroupTail)tail).groupIndex,
2969                                              capturingGroup);
2970                 return head;
2971             } else { // Non-deterministic
2972                 int temp = ((GroupHead) head).localIndex;
2973                 Loop loop;
2974                 if (curly.type == GREEDY)
2975                     loop = new Loop(this.localCount, temp);
2976                 else  // Reluctant Curly
2977                     loop = new LazyLoop(this.localCount, temp);
2978                 Prolog prolog = new Prolog(loop);
2979                 this.localCount += 1;
2980                 loop.cmin = curly.cmin;
2981                 loop.cmax = curly.cmax;
2982                 loop.body = head;
2983                 tail.next = loop;
2984                 root = loop;
2985                 return prolog; // Dual return
2986             }
2987         }
2988         throw error("Internal logic error");
2989     }
2990 
2991     /**
2992      * Create group head and tail nodes using double return. If the group is
2993      * created with anonymous true then it is a pure group and should not
2994      * affect group counting.
2995      */
2996     private Node createGroup(boolean anonymous) {
2997         int localIndex = localCount++;
2998         int groupIndex = 0;
2999         if (!anonymous)
3000             groupIndex = capturingGroupCount++;
3001         GroupHead head = new GroupHead(localIndex);
3002         root = new GroupTail(localIndex, groupIndex);
3003         if (!anonymous && groupIndex < 10)
3004             groupNodes[groupIndex] = head;
3005         return head;
3006     }
3007 
3008     @SuppressWarnings("fallthrough")
3009     /**
3010      * Parses inlined match flags and set them appropriately.
3011      */
3012     private void addFlag() {
3013         int ch = peek();
3014         for (;;) {
3015             switch (ch) {
3016             case 'i':
3017                 flags |= CASE_INSENSITIVE;
3018                 break;
3019             case 'm':
3020                 flags |= MULTILINE;
3021                 break;
3022             case 's':
3023                 flags |= DOTALL;
3024                 break;
3025             case 'd':
3026                 flags |= UNIX_LINES;
3027                 break;
3028             case 'u':
3029                 flags |= UNICODE_CASE;
3030                 break;
3031             case 'c':
3032                 flags |= CANON_EQ;
3033                 break;
3034             case 'x':
3035                 flags |= COMMENTS;
3036                 break;
3037             case 'U':
3038                 flags |= (UNICODE_CHARACTER_CLASS | UNICODE_CASE);
3039                 break;
3040             case '-': // subFlag then fall through
3041                 ch = next();
3042                 subFlag();
3043             default:
3044                 return;
3045             }
3046             ch = next();
3047         }
3048     }
3049 
3050     @SuppressWarnings("fallthrough")
3051     /**
3052      * Parses the second part of inlined match flags and turns off
3053      * flags appropriately.
3054      */
3055     private void subFlag() {
3056         int ch = peek();
3057         for (;;) {
3058             switch (ch) {
3059             case 'i':
3060                 flags &= ~CASE_INSENSITIVE;
3061                 break;
3062             case 'm':
3063                 flags &= ~MULTILINE;
3064                 break;
3065             case 's':
3066                 flags &= ~DOTALL;
3067                 break;
3068             case 'd':
3069                 flags &= ~UNIX_LINES;
3070                 break;
3071             case 'u':
3072                 flags &= ~UNICODE_CASE;
3073                 break;
3074             case 'c':
3075                 flags &= ~CANON_EQ;
3076                 break;
3077             case 'x':
3078                 flags &= ~COMMENTS;
3079                 break;
3080             case 'U':
3081                 flags &= ~(UNICODE_CHARACTER_CLASS | UNICODE_CASE);
3082             default:
3083                 return;
3084             }
3085             ch = next();
3086         }
3087     }
3088 
3089     static final int MAX_REPS   = 0x7FFFFFFF;
3090 
3091     static final int GREEDY     = 0;
3092 
3093     static final int LAZY       = 1;
3094 
3095     static final int POSSESSIVE = 2;
3096 
3097     static final int INDEPENDENT = 3;
3098 
3099     /**
3100      * Processes repetition. If the next character peeked is a quantifier
3101      * then new nodes must be appended to handle the repetition.
3102      * Prev could be a single or a group, so it could be a chain of nodes.
3103      */
3104     private Node closure(Node prev) {
3105         Node atom;
3106         int ch = peek();
3107         switch (ch) {
3108         case '?':
3109             ch = next();
3110             if (ch == '?') {
3111                 next();
3112                 return new Ques(prev, LAZY);
3113             } else if (ch == '+') {
3114                 next();
3115                 return new Ques(prev, POSSESSIVE);
3116             }
3117             return new Ques(prev, GREEDY);
3118         case '*':
3119             ch = next();
3120             if (ch == '?') {
3121                 next();
3122                 return new Curly(prev, 0, MAX_REPS, LAZY);
3123             } else if (ch == '+') {
3124                 next();
3125                 return new Curly(prev, 0, MAX_REPS, POSSESSIVE);
3126             }
3127             return new Curly(prev, 0, MAX_REPS, GREEDY);
3128         case '+':
3129             ch = next();
3130             if (ch == '?') {
3131                 next();
3132                 return new Curly(prev, 1, MAX_REPS, LAZY);
3133             } else if (ch == '+') {
3134                 next();
3135                 return new Curly(prev, 1, MAX_REPS, POSSESSIVE);
3136             }
3137             return new Curly(prev, 1, MAX_REPS, GREEDY);
3138         case '{':
3139             ch = temp[cursor+1];
3140             if (ASCII.isDigit(ch)) {
3141                 skip();
3142                 int cmin = 0;
3143                 do {
3144                     cmin = cmin * 10 + (ch - '0');
3145                 } while (ASCII.isDigit(ch = read()));
3146                 int cmax = cmin;
3147                 if (ch == ',') {
3148                     ch = read();
3149                     cmax = MAX_REPS;
3150                     if (ch != '}') {
3151                         cmax = 0;
3152                         while (ASCII.isDigit(ch)) {
3153                             cmax = cmax * 10 + (ch - '0');
3154                             ch = read();
3155                         }
3156                     }
3157                 }
3158                 if (ch != '}')
3159                     throw error("Unclosed counted closure");
3160                 if (((cmin) | (cmax) | (cmax - cmin)) < 0)
3161                     throw error("Illegal repetition range");
3162                 Curly curly;
3163                 ch = peek();
3164                 if (ch == '?') {
3165                     next();
3166                     curly = new Curly(prev, cmin, cmax, LAZY);
3167                 } else if (ch == '+') {
3168                     next();
3169                     curly = new Curly(prev, cmin, cmax, POSSESSIVE);
3170                 } else {
3171                     curly = new Curly(prev, cmin, cmax, GREEDY);
3172                 }
3173                 return curly;
3174             } else {
3175                 throw error("Illegal repetition");
3176             }
3177         default:
3178             return prev;
3179         }
3180     }
3181 
3182     /**
3183      *  Utility method for parsing control escape sequences.
3184      */
3185     private int c() {
3186         if (cursor < patternLength) {
3187             return read() ^ 64;
3188         }
3189         throw error("Illegal control escape sequence");
3190     }
3191 
3192     /**
3193      *  Utility method for parsing octal escape sequences.
3194      */
3195     private int o() {
3196         int n = read();
3197         if (((n-'0')|('7'-n)) >= 0) {
3198             int m = read();
3199             if (((m-'0')|('7'-m)) >= 0) {
3200                 int o = read();
3201                 if ((((o-'0')|('7'-o)) >= 0) && (((n-'0')|('3'-n)) >= 0)) {
3202                     return (n - '0') * 64 + (m - '0') * 8 + (o - '0');
3203                 }
3204                 unread();
3205                 return (n - '0') * 8 + (m - '0');
3206             }
3207             unread();
3208             return (n - '0');
3209         }
3210         throw error("Illegal octal escape sequence");
3211     }
3212 
3213     /**
3214      *  Utility method for parsing hexadecimal escape sequences.
3215      */
3216     private int x() {
3217         int n = read();
3218         if (ASCII.isHexDigit(n)) {
3219             int m = read();
3220             if (ASCII.isHexDigit(m)) {
3221                 return ASCII.toDigit(n) * 16 + ASCII.toDigit(m);
3222             }
3223         } else if (n == '{' && ASCII.isHexDigit(peek())) {
3224             int ch = 0;
3225             while (ASCII.isHexDigit(n = read())) {
3226                 ch = (ch << 4) + ASCII.toDigit(n);
3227                 if (ch > Character.MAX_CODE_POINT)
3228                     throw error("Hexadecimal codepoint is too big");
3229             }
3230             if (n != '}')
3231                 throw error("Unclosed hexadecimal escape sequence");
3232             return ch;
3233         }
3234         throw error("Illegal hexadecimal escape sequence");
3235     }
3236 
3237     /**
3238      *  Utility method for parsing unicode escape sequences.
3239      */
3240     private int cursor() {
3241         return cursor;
3242     }
3243 
3244     private void setcursor(int pos) {
3245         cursor = pos;
3246     }
3247 
3248     private int uxxxx() {
3249         int n = 0;
3250         for (int i = 0; i < 4; i++) {
3251             int ch = read();
3252             if (!ASCII.isHexDigit(ch)) {
3253                 throw error("Illegal Unicode escape sequence");
3254             }
3255             n = n * 16 + ASCII.toDigit(ch);
3256         }
3257         return n;
3258     }
3259 
3260     private int u() {
3261         int n = uxxxx();
3262         if (Character.isHighSurrogate((char)n)) {
3263             int cur = cursor();
3264             if (read() == '\\' && read() == 'u') {
3265                 int n2 = uxxxx();
3266                 if (Character.isLowSurrogate((char)n2))
3267                     return Character.toCodePoint((char)n, (char)n2);
3268             }
3269             setcursor(cur);
3270         }
3271         return n;
3272     }
3273 
3274     //
3275     // Utility methods for code point support
3276     //
3277 
3278     private static final int countChars(CharSequence seq, int index,
3279                                         int lengthInCodePoints) {
3280         // optimization
3281         if (lengthInCodePoints == 1 && !Character.isHighSurrogate(seq.charAt(index))) {
3282             assert (index >= 0 && index < seq.length());
3283             return 1;
3284         }
3285         int length = seq.length();
3286         int x = index;
3287         if (lengthInCodePoints >= 0) {
3288             assert (index >= 0 && index < length);
3289             for (int i = 0; x < length && i < lengthInCodePoints; i++) {
3290                 if (Character.isHighSurrogate(seq.charAt(x++))) {
3291                     if (x < length && Character.isLowSurrogate(seq.charAt(x))) {
3292                         x++;
3293                     }
3294                 }
3295             }
3296             return x - index;
3297         }
3298 
3299         assert (index >= 0 && index <= length);
3300         if (index == 0) {
3301             return 0;
3302         }
3303         int len = -lengthInCodePoints;
3304         for (int i = 0; x > 0 && i < len; i++) {
3305             if (Character.isLowSurrogate(seq.charAt(--x))) {
3306                 if (x > 0 && Character.isHighSurrogate(seq.charAt(x-1))) {
3307                     x--;
3308                 }
3309             }
3310         }
3311         return index - x;
3312     }
3313 
3314     private static final int countCodePoints(CharSequence seq) {
3315         int length = seq.length();
3316         int n = 0;
3317         for (int i = 0; i < length; ) {
3318             n++;
3319             if (Character.isHighSurrogate(seq.charAt(i++))) {
3320                 if (i < length && Character.isLowSurrogate(seq.charAt(i))) {
3321                     i++;
3322                 }
3323             }
3324         }
3325         return n;
3326     }
3327 
3328     /**
3329      *  Creates a bit vector for matching Latin-1 values. A normal BitClass
3330      *  never matches values above Latin-1, and a complemented BitClass always
3331      *  matches values above Latin-1.
3332      */
3333     private static final class BitClass extends BmpCharProperty {
3334         final boolean[] bits;
3335         BitClass() { bits = new boolean[256]; }
3336         private BitClass(boolean[] bits) { this.bits = bits; }
3337         BitClass add(int c, int flags) {
3338             assert c >= 0 && c <= 255;
3339             if ((flags & CASE_INSENSITIVE) != 0) {
3340                 if (ASCII.isAscii(c)) {
3341                     bits[ASCII.toUpper(c)] = true;
3342                     bits[ASCII.toLower(c)] = true;
3343                 } else if ((flags & UNICODE_CASE) != 0) {
3344                     bits[Character.toLowerCase(c)] = true;
3345                     bits[Character.toUpperCase(c)] = true;
3346                 }
3347             }
3348             bits[c] = true;
3349             return this;
3350         }
3351         boolean isSatisfiedBy(int ch) {
3352             return ch < 256 && bits[ch];
3353         }
3354     }
3355 
3356     /**
3357      *  Returns a suitably optimized, single character matcher.
3358      */
3359     private CharProperty newSingle(final int ch) {
3360         if (has(CASE_INSENSITIVE)) {
3361             int lower, upper;
3362             if (has(UNICODE_CASE)) {
3363                 upper = Character.toUpperCase(ch);
3364                 lower = Character.toLowerCase(upper);
3365                 if (upper != lower)
3366                     return new SingleU(lower);
3367             } else if (ASCII.isAscii(ch)) {
3368                 lower = ASCII.toLower(ch);
3369                 upper = ASCII.toUpper(ch);
3370                 if (lower != upper)
3371                     return new SingleI(lower, upper);
3372             }
3373         }
3374         if (isSupplementary(ch))
3375             return new SingleS(ch);    // Match a given Unicode character
3376         return new Single(ch);         // Match a given BMP character
3377     }
3378 
3379     /**
3380      *  Utility method for creating a string slice matcher.
3381      */
3382     private Node newSlice(int[] buf, int count, boolean hasSupplementary) {
3383         int[] tmp = new int[count];
3384         if (has(CASE_INSENSITIVE)) {
3385             if (has(UNICODE_CASE)) {
3386                 for (int i = 0; i < count; i++) {
3387                     tmp[i] = Character.toLowerCase(
3388                                  Character.toUpperCase(buf[i]));
3389                 }
3390                 return hasSupplementary? new SliceUS(tmp) : new SliceU(tmp);
3391             }
3392             for (int i = 0; i < count; i++) {
3393                 tmp[i] = ASCII.toLower(buf[i]);
3394             }
3395             return hasSupplementary? new SliceIS(tmp) : new SliceI(tmp);
3396         }
3397         for (int i = 0; i < count; i++) {
3398             tmp[i] = buf[i];
3399         }
3400         return hasSupplementary ? new SliceS(tmp) : new Slice(tmp);
3401     }
3402 
3403     /**
3404      * The following classes are the building components of the object
3405      * tree that represents a compiled regular expression. The object tree
3406      * is made of individual elements that handle constructs in the Pattern.
3407      * Each type of object knows how to match its equivalent construct with
3408      * the match() method.
3409      */
3410 
3411     /**
3412      * Base class for all node classes. Subclasses should override the match()
3413      * method as appropriate. This class is an accepting node, so its match()
3414      * always returns true.
3415      */
3416     static class Node extends Object {
3417         Node next;
3418         Node() {
3419             next = Pattern.accept;
3420         }
3421         /**
3422          * This method implements the classic accept node.
3423          */
3424         boolean match(Matcher matcher, int i, CharSequence seq) {
3425             matcher.last = i;
3426             matcher.groups[0] = matcher.first;
3427             matcher.groups[1] = matcher.last;
3428             return true;
3429         }
3430         /**
3431          * This method is good for all zero length assertions.
3432          */
3433         boolean study(TreeInfo info) {
3434             if (next != null) {
3435                 return next.study(info);
3436             } else {
3437                 return info.deterministic;
3438             }
3439         }
3440     }
3441 
3442     static class LastNode extends Node {
3443         /**
3444          * This method implements the classic accept node with
3445          * the addition of a check to see if the match occurred
3446          * using all of the input.
3447          */
3448         boolean match(Matcher matcher, int i, CharSequence seq) {
3449             if (matcher.acceptMode == Matcher.ENDANCHOR && i != matcher.to)
3450                 return false;
3451             matcher.last = i;
3452             matcher.groups[0] = matcher.first;
3453             matcher.groups[1] = matcher.last;
3454             return true;
3455         }
3456     }
3457 
3458     /**
3459      * Used for REs that can start anywhere within the input string.
3460      * This basically tries to match repeatedly at each spot in the
3461      * input string, moving forward after each try. An anchored search
3462      * or a BnM will bypass this node completely.
3463      */
3464     static class Start extends Node {
3465         int minLength;
3466         Start(Node node) {
3467             this.next = node;
3468             TreeInfo info = new TreeInfo();
3469             next.study(info);
3470             minLength = info.minLength;
3471         }
3472         boolean match(Matcher matcher, int i, CharSequence seq) {
3473             if (i > matcher.to - minLength) {
3474                 matcher.hitEnd = true;
3475                 return false;
3476             }
3477             int guard = matcher.to - minLength;
3478             for (; i <= guard; i++) {
3479                 if (next.match(matcher, i, seq)) {
3480                     matcher.first = i;
3481                     matcher.groups[0] = matcher.first;
3482                     matcher.groups[1] = matcher.last;
3483                     return true;
3484                 }
3485             }
3486             matcher.hitEnd = true;
3487             return false;
3488         }
3489         boolean study(TreeInfo info) {
3490             next.study(info);
3491             info.maxValid = false;
3492             info.deterministic = false;
3493             return false;
3494         }
3495     }
3496 
3497     /*
3498      * StartS supports supplementary characters, including unpaired surrogates.
3499      */
3500     static final class StartS extends Start {
3501         StartS(Node node) {
3502             super(node);
3503         }
3504         boolean match(Matcher matcher, int i, CharSequence seq) {
3505             if (i > matcher.to - minLength) {
3506                 matcher.hitEnd = true;
3507                 return false;
3508             }
3509             int guard = matcher.to - minLength;
3510             while (i <= guard) {
3511                 //if ((ret = next.match(matcher, i, seq)) || i == guard)
3512                 if (next.match(matcher, i, seq)) {
3513                     matcher.first = i;
3514                     matcher.groups[0] = matcher.first;
3515                     matcher.groups[1] = matcher.last;
3516                     return true;
3517                 }
3518                 if (i == guard)
3519                     break;
3520                 // Optimization to move to the next character. This is
3521                 // faster than countChars(seq, i, 1).
3522                 if (Character.isHighSurrogate(seq.charAt(i++))) {
3523                     if (i < seq.length() &&
3524                         Character.isLowSurrogate(seq.charAt(i))) {
3525                         i++;
3526                     }
3527                 }
3528             }
3529             matcher.hitEnd = true;
3530             return false;
3531         }
3532     }
3533 
3534     /**
3535      * Node to anchor at the beginning of input. This object implements the
3536      * match for a \A sequence, and the caret anchor will use this if not in
3537      * multiline mode.
3538      */
3539     static final class Begin extends Node {
3540         boolean match(Matcher matcher, int i, CharSequence seq) {
3541             int fromIndex = (matcher.anchoringBounds) ?
3542                 matcher.from : 0;
3543             if (i == fromIndex && next.match(matcher, i, seq)) {
3544                 matcher.first = i;
3545                 matcher.groups[0] = i;
3546                 matcher.groups[1] = matcher.last;
3547                 return true;
3548             } else {
3549                 return false;
3550             }
3551         }
3552     }
3553 
3554     /**
3555      * Node to anchor at the end of input. This is the absolute end, so this
3556      * should not match at the last newline before the end as $ will.
3557      */
3558     static final class End extends Node {
3559         boolean match(Matcher matcher, int i, CharSequence seq) {
3560             int endIndex = (matcher.anchoringBounds) ?
3561                 matcher.to : matcher.getTextLength();
3562             if (i == endIndex) {
3563                 matcher.hitEnd = true;
3564                 return next.match(matcher, i, seq);
3565             }
3566             return false;
3567         }
3568     }
3569 
3570     /**
3571      * Node to anchor at the beginning of a line. This is essentially the
3572      * object to match for the multiline ^.
3573      */
3574     static final class Caret extends Node {
3575         boolean match(Matcher matcher, int i, CharSequence seq) {
3576             int startIndex = matcher.from;
3577             int endIndex = matcher.to;
3578             if (!matcher.anchoringBounds) {
3579                 startIndex = 0;
3580                 endIndex = matcher.getTextLength();
3581             }
3582             // Perl does not match ^ at end of input even after newline
3583             if (i == endIndex) {
3584                 matcher.hitEnd = true;
3585                 return false;
3586             }
3587             if (i > startIndex) {
3588                 char ch = seq.charAt(i-1);
3589                 if (ch != '\n' && ch != '\r'
3590                     && (ch|1) != '\u2029'
3591                     && ch != '\u0085' ) {
3592                     return false;
3593                 }
3594                 // Should treat /r/n as one newline
3595                 if (ch == '\r' && seq.charAt(i) == '\n')
3596                     return false;
3597             }
3598             return next.match(matcher, i, seq);
3599         }
3600     }
3601 
3602     /**
3603      * Node to anchor at the beginning of a line when in unixdot mode.
3604      */
3605     static final class UnixCaret extends Node {
3606         boolean match(Matcher matcher, int i, CharSequence seq) {
3607             int startIndex = matcher.from;
3608             int endIndex = matcher.to;
3609             if (!matcher.anchoringBounds) {
3610                 startIndex = 0;
3611                 endIndex = matcher.getTextLength();
3612             }
3613             // Perl does not match ^ at end of input even after newline
3614             if (i == endIndex) {
3615                 matcher.hitEnd = true;
3616                 return false;
3617             }
3618             if (i > startIndex) {
3619                 char ch = seq.charAt(i-1);
3620                 if (ch != '\n') {
3621                     return false;
3622                 }
3623             }
3624             return next.match(matcher, i, seq);
3625         }
3626     }
3627 
3628     /**
3629      * Node to match the location where the last match ended.
3630      * This is used for the \G construct.
3631      */
3632     static final class LastMatch extends Node {
3633         boolean match(Matcher matcher, int i, CharSequence seq) {
3634             if (i != matcher.oldLast)
3635                 return false;
3636             return next.match(matcher, i, seq);
3637         }
3638     }
3639 
3640     /**
3641      * Node to anchor at the end of a line or the end of input based on the
3642      * multiline mode.
3643      *
3644      * When not in multiline mode, the $ can only match at the very end
3645      * of the input, unless the input ends in a line terminator in which
3646      * it matches right before the last line terminator.
3647      *
3648      * Note that \r\n is considered an atomic line terminator.
3649      *
3650      * Like ^ the $ operator matches at a position, it does not match the
3651      * line terminators themselves.
3652      */
3653     static final class Dollar extends Node {
3654         boolean multiline;
3655         Dollar(boolean mul) {
3656             multiline = mul;
3657         }
3658         boolean match(Matcher matcher, int i, CharSequence seq) {
3659             int endIndex = (matcher.anchoringBounds) ?
3660                 matcher.to : matcher.getTextLength();
3661             if (!multiline) {
3662                 if (i < endIndex - 2)
3663                     return false;
3664                 if (i == endIndex - 2) {
3665                     char ch = seq.charAt(i);
3666                     if (ch != '\r')
3667                         return false;
3668                     ch = seq.charAt(i + 1);
3669                     if (ch != '\n')
3670                         return false;
3671                 }
3672             }
3673             // Matches before any line terminator; also matches at the
3674             // end of input
3675             // Before line terminator:
3676             // If multiline, we match here no matter what
3677             // If not multiline, fall through so that the end
3678             // is marked as hit; this must be a /r/n or a /n
3679             // at the very end so the end was hit; more input
3680             // could make this not match here
3681             if (i < endIndex) {
3682                 char ch = seq.charAt(i);
3683                  if (ch == '\n') {
3684                      // No match between \r\n
3685                      if (i > 0 && seq.charAt(i-1) == '\r')
3686                          return false;
3687                      if (multiline)
3688                          return next.match(matcher, i, seq);
3689                  } else if (ch == '\r' || ch == '\u0085' ||
3690                             (ch|1) == '\u2029') {
3691                      if (multiline)
3692                          return next.match(matcher, i, seq);
3693                  } else { // No line terminator, no match
3694                      return false;
3695                  }
3696             }
3697             // Matched at current end so hit end
3698             matcher.hitEnd = true;
3699             // If a $ matches because of end of input, then more input
3700             // could cause it to fail!
3701             matcher.requireEnd = true;
3702             return next.match(matcher, i, seq);
3703         }
3704         boolean study(TreeInfo info) {
3705             next.study(info);
3706             return info.deterministic;
3707         }
3708     }
3709 
3710     /**
3711      * Node to anchor at the end of a line or the end of input based on the
3712      * multiline mode when in unix lines mode.
3713      */
3714     static final class UnixDollar extends Node {
3715         boolean multiline;
3716         UnixDollar(boolean mul) {
3717             multiline = mul;
3718         }
3719         boolean match(Matcher matcher, int i, CharSequence seq) {
3720             int endIndex = (matcher.anchoringBounds) ?
3721                 matcher.to : matcher.getTextLength();
3722             if (i < endIndex) {
3723                 char ch = seq.charAt(i);
3724                 if (ch == '\n') {
3725                     // If not multiline, then only possible to
3726                     // match at very end or one before end
3727                     if (multiline == false && i != endIndex - 1)
3728                         return false;
3729                     // If multiline return next.match without setting
3730                     // matcher.hitEnd
3731                     if (multiline)
3732                         return next.match(matcher, i, seq);
3733                 } else {
3734                     return false;
3735                 }
3736             }
3737             // Matching because at the end or 1 before the end;
3738             // more input could change this so set hitEnd
3739             matcher.hitEnd = true;
3740             // If a $ matches because of end of input, then more input
3741             // could cause it to fail!
3742             matcher.requireEnd = true;
3743             return next.match(matcher, i, seq);
3744         }
3745         boolean study(TreeInfo info) {
3746             next.study(info);
3747             return info.deterministic;
3748         }
3749     }
3750 
3751     /**
3752      * Node class that matches a Unicode line ending '\R'
3753      */
3754     static final class LineEnding extends Node {
3755         boolean match(Matcher matcher, int i, CharSequence seq) {
3756             // (u+000Du+000A|[u+000Au+000Bu+000Cu+000Du+0085u+2028u+2029])
3757             if (i < matcher.to) {
3758                 int ch = seq.charAt(i);
3759                 if (ch == 0x0A || ch == 0x0B || ch == 0x0C ||
3760                     ch == 0x85 || ch == 0x2028 || ch == 0x2029)
3761                     return next.match(matcher, i + 1, seq);
3762                 if (ch == 0x0D) {
3763                     i++;
3764                     if (i < matcher.to && seq.charAt(i) == 0x0A)
3765                         i++;
3766                     return next.match(matcher, i, seq);
3767                 }
3768             } else {
3769                 matcher.hitEnd = true;
3770             }
3771             return false;
3772         }
3773         boolean study(TreeInfo info) {
3774             info.minLength++;
3775             info.maxLength += 2;
3776             return next.study(info);
3777         }
3778     }
3779 
3780     /**
3781      * Abstract node class to match one character satisfying some
3782      * boolean property.
3783      */
3784     private static abstract class CharProperty extends Node {
3785         abstract boolean isSatisfiedBy(int ch);
3786         CharProperty complement() {
3787             return new CharProperty() {
3788                     boolean isSatisfiedBy(int ch) {
3789                         return ! CharProperty.this.isSatisfiedBy(ch);}};
3790         }
3791         boolean match(Matcher matcher, int i, CharSequence seq) {
3792             if (i < matcher.to) {
3793                 int ch = Character.codePointAt(seq, i);
3794                 return isSatisfiedBy(ch)
3795                     && next.match(matcher, i+Character.charCount(ch), seq);
3796             } else {
3797                 matcher.hitEnd = true;
3798                 return false;
3799             }
3800         }
3801         boolean study(TreeInfo info) {
3802             info.minLength++;
3803             info.maxLength++;
3804             return next.study(info);
3805         }
3806     }
3807 
3808     /**
3809      * Optimized version of CharProperty that works only for
3810      * properties never satisfied by Supplementary characters.
3811      */
3812     private static abstract class BmpCharProperty extends CharProperty {
3813         boolean match(Matcher matcher, int i, CharSequence seq) {
3814             if (i < matcher.to) {
3815                 return isSatisfiedBy(seq.charAt(i))
3816                     && next.match(matcher, i+1, seq);
3817             } else {
3818                 matcher.hitEnd = true;
3819                 return false;
3820             }
3821         }
3822     }
3823 
3824     /**
3825      * Node class that matches a Supplementary Unicode character
3826      */
3827     static final class SingleS extends CharProperty {
3828         final int c;
3829         SingleS(int c) { this.c = c; }
3830         boolean isSatisfiedBy(int ch) {
3831             return ch == c;
3832         }
3833     }
3834 
3835     /**
3836      * Optimization -- matches a given BMP character
3837      */
3838     static final class Single extends BmpCharProperty {
3839         final int c;
3840         Single(int c) { this.c = c; }
3841         boolean isSatisfiedBy(int ch) {
3842             return ch == c;
3843         }
3844     }
3845 
3846     /**
3847      * Case insensitive matches a given BMP character
3848      */
3849     static final class SingleI extends BmpCharProperty {
3850         final int lower;
3851         final int upper;
3852         SingleI(int lower, int upper) {
3853             this.lower = lower;
3854             this.upper = upper;
3855         }
3856         boolean isSatisfiedBy(int ch) {
3857             return ch == lower || ch == upper;
3858         }
3859     }
3860 
3861     /**
3862      * Unicode case insensitive matches a given Unicode character
3863      */
3864     static final class SingleU extends CharProperty {
3865         final int lower;
3866         SingleU(int lower) {
3867             this.lower = lower;
3868         }
3869         boolean isSatisfiedBy(int ch) {
3870             return lower == ch ||
3871                 lower == Character.toLowerCase(Character.toUpperCase(ch));
3872         }
3873     }
3874 
3875     /**
3876      * Node class that matches a Unicode block.
3877      */
3878     static final class Block extends CharProperty {
3879         final Character.UnicodeBlock block;
3880         Block(Character.UnicodeBlock block) {
3881             this.block = block;
3882         }
3883         boolean isSatisfiedBy(int ch) {
3884             return block == Character.UnicodeBlock.of(ch);
3885         }
3886     }
3887 
3888     /**
3889      * Node class that matches a Unicode script
3890      */
3891     static final class Script extends CharProperty {
3892         final Character.UnicodeScript script;
3893         Script(Character.UnicodeScript script) {
3894             this.script = script;
3895         }
3896         boolean isSatisfiedBy(int ch) {
3897             return script == Character.UnicodeScript.of(ch);
3898         }
3899     }
3900 
3901     /**
3902      * Node class that matches a Unicode category.
3903      */
3904     static final class Category extends CharProperty {
3905         final int typeMask;
3906         Category(int typeMask) { this.typeMask = typeMask; }
3907         boolean isSatisfiedBy(int ch) {
3908             return (typeMask & (1 << Character.getType(ch))) != 0;
3909         }
3910     }
3911 
3912     /**
3913      * Node class that matches a Unicode "type"
3914      */
3915     static final class Utype extends CharProperty {
3916         final UnicodeProp uprop;
3917         Utype(UnicodeProp uprop) { this.uprop = uprop; }
3918         boolean isSatisfiedBy(int ch) {
3919             return uprop.is(ch);
3920         }
3921     }
3922 
3923     /**
3924      * Node class that matches a POSIX type.
3925      */
3926     static final class Ctype extends BmpCharProperty {
3927         final int ctype;
3928         Ctype(int ctype) { this.ctype = ctype; }
3929         boolean isSatisfiedBy(int ch) {
3930             return ch < 128 && ASCII.isType(ch, ctype);
3931         }
3932     }
3933 
3934     /**
3935      * Node class that matches a Perl vertical whitespace
3936      */
3937     static final class VertWS extends BmpCharProperty {
3938         boolean isSatisfiedBy(int cp) {
3939             return (cp >= 0x0A && cp <= 0x0D) ||
3940                    cp == 0x85 || cp == 0x2028 || cp == 0x2029;
3941         }
3942     }
3943 
3944     /**
3945      * Node class that matches a Perl horizontal whitespace
3946      */
3947     static final class HorizWS extends BmpCharProperty {
3948         boolean isSatisfiedBy(int cp) {
3949             return cp == 0x09 || cp == 0x20 || cp == 0xa0 ||
3950                    cp == 0x1680 || cp == 0x180e ||
3951                    cp >= 0x2000 && cp <= 0x200a ||
3952                    cp == 0x202f || cp == 0x205f || cp == 0x3000;
3953         }
3954     }
3955 
3956     /**
3957      * Base class for all Slice nodes
3958      */
3959     static class SliceNode extends Node {
3960         int[] buffer;
3961         SliceNode(int[] buf) {
3962             buffer = buf;
3963         }
3964         boolean study(TreeInfo info) {
3965             info.minLength += buffer.length;
3966             info.maxLength += buffer.length;
3967             return next.study(info);
3968         }
3969     }
3970 
3971     /**
3972      * Node class for a case sensitive/BMP-only sequence of literal
3973      * characters.
3974      */
3975     static class Slice extends SliceNode {
3976         Slice(int[] buf) {
3977             super(buf);
3978         }
3979         boolean match(Matcher matcher, int i, CharSequence seq) {
3980             int[] buf = buffer;
3981             int len = buf.length;
3982             for (int j=0; j<len; j++) {
3983                 if ((i+j) >= matcher.to) {
3984                     matcher.hitEnd = true;
3985                     return false;
3986                 }
3987                 if (buf[j] != seq.charAt(i+j))
3988                     return false;
3989             }
3990             return next.match(matcher, i+len, seq);
3991         }
3992     }
3993 
3994     /**
3995      * Node class for a case_insensitive/BMP-only sequence of literal
3996      * characters.
3997      */
3998     static class SliceI extends SliceNode {
3999         SliceI(int[] buf) {
4000             super(buf);
4001         }
4002         boolean match(Matcher matcher, int i, CharSequence seq) {
4003             int[] buf = buffer;
4004             int len = buf.length;
4005             for (int j=0; j<len; j++) {
4006                 if ((i+j) >= matcher.to) {
4007                     matcher.hitEnd = true;
4008                     return false;
4009                 }
4010                 int c = seq.charAt(i+j);
4011                 if (buf[j] != c &&
4012                     buf[j] != ASCII.toLower(c))
4013                     return false;
4014             }
4015             return next.match(matcher, i+len, seq);
4016         }
4017     }
4018 
4019     /**
4020      * Node class for a unicode_case_insensitive/BMP-only sequence of
4021      * literal characters. Uses unicode case folding.
4022      */
4023     static final class SliceU extends SliceNode {
4024         SliceU(int[] buf) {
4025             super(buf);
4026         }
4027         boolean match(Matcher matcher, int i, CharSequence seq) {
4028             int[] buf = buffer;
4029             int len = buf.length;
4030             for (int j=0; j<len; j++) {
4031                 if ((i+j) >= matcher.to) {
4032                     matcher.hitEnd = true;
4033                     return false;
4034                 }
4035                 int c = seq.charAt(i+j);
4036                 if (buf[j] != c &&
4037                     buf[j] != Character.toLowerCase(Character.toUpperCase(c)))
4038                     return false;
4039             }
4040             return next.match(matcher, i+len, seq);
4041         }
4042     }
4043 
4044     /**
4045      * Node class for a case sensitive sequence of literal characters
4046      * including supplementary characters.
4047      */
4048     static final class SliceS extends Slice {
4049         SliceS(int[] buf) {
4050             super(buf);
4051         }
4052         boolean match(Matcher matcher, int i, CharSequence seq) {
4053             int[] buf = buffer;
4054             int x = i;
4055             for (int j = 0; j < buf.length; j++) {
4056                 if (x >= matcher.to) {
4057                     matcher.hitEnd = true;
4058                     return false;
4059                 }
4060                 int c = Character.codePointAt(seq, x);
4061                 if (buf[j] != c)
4062                     return false;
4063                 x += Character.charCount(c);
4064                 if (x > matcher.to) {
4065                     matcher.hitEnd = true;
4066                     return false;
4067                 }
4068             }
4069             return next.match(matcher, x, seq);
4070         }
4071     }
4072 
4073     /**
4074      * Node class for a case insensitive sequence of literal characters
4075      * including supplementary characters.
4076      */
4077     static class SliceIS extends SliceNode {
4078         SliceIS(int[] buf) {
4079             super(buf);
4080         }
4081         int toLower(int c) {
4082             return ASCII.toLower(c);
4083         }
4084         boolean match(Matcher matcher, int i, CharSequence seq) {
4085             int[] buf = buffer;
4086             int x = i;
4087             for (int j = 0; j < buf.length; j++) {
4088                 if (x >= matcher.to) {
4089                     matcher.hitEnd = true;
4090                     return false;
4091                 }
4092                 int c = Character.codePointAt(seq, x);
4093                 if (buf[j] != c && buf[j] != toLower(c))
4094                     return false;
4095                 x += Character.charCount(c);
4096                 if (x > matcher.to) {
4097                     matcher.hitEnd = true;
4098                     return false;
4099                 }
4100             }
4101             return next.match(matcher, x, seq);
4102         }
4103     }
4104 
4105     /**
4106      * Node class for a case insensitive sequence of literal characters.
4107      * Uses unicode case folding.
4108      */
4109     static final class SliceUS extends SliceIS {
4110         SliceUS(int[] buf) {
4111             super(buf);
4112         }
4113         int toLower(int c) {
4114             return Character.toLowerCase(Character.toUpperCase(c));
4115         }
4116     }
4117 
4118     private static boolean inRange(int lower, int ch, int upper) {
4119         return lower <= ch && ch <= upper;
4120     }
4121 
4122     /**
4123      * Returns node for matching characters within an explicit value range.
4124      */
4125     private static CharProperty rangeFor(final int lower,
4126                                          final int upper) {
4127         return new CharProperty() {
4128                 boolean isSatisfiedBy(int ch) {
4129                     return inRange(lower, ch, upper);}};
4130     }
4131 
4132     /**
4133      * Returns node for matching characters within an explicit value
4134      * range in a case insensitive manner.
4135      */
4136     private CharProperty caseInsensitiveRangeFor(final int lower,
4137                                                  final int upper) {
4138         if (has(UNICODE_CASE))
4139             return new CharProperty() {
4140                 boolean isSatisfiedBy(int ch) {
4141                     if (inRange(lower, ch, upper))
4142                         return true;
4143                     int up = Character.toUpperCase(ch);
4144                     return inRange(lower, up, upper) ||
4145                            inRange(lower, Character.toLowerCase(up), upper);}};
4146         return new CharProperty() {
4147             boolean isSatisfiedBy(int ch) {
4148                 return inRange(lower, ch, upper) ||
4149                     ASCII.isAscii(ch) &&
4150                         (inRange(lower, ASCII.toUpper(ch), upper) ||
4151                          inRange(lower, ASCII.toLower(ch), upper));
4152             }};
4153     }
4154 
4155     /**
4156      * Implements the Unicode category ALL and the dot metacharacter when
4157      * in dotall mode.
4158      */
4159     static final class All extends CharProperty {
4160         boolean isSatisfiedBy(int ch) {
4161             return true;
4162         }
4163     }
4164 
4165     /**
4166      * Node class for the dot metacharacter when dotall is not enabled.
4167      */
4168     static final class Dot extends CharProperty {
4169         boolean isSatisfiedBy(int ch) {
4170             return (ch != '\n' && ch != '\r'
4171                     && (ch|1) != '\u2029'
4172                     && ch != '\u0085');
4173         }
4174     }
4175 
4176     /**
4177      * Node class for the dot metacharacter when dotall is not enabled
4178      * but UNIX_LINES is enabled.
4179      */
4180     static final class UnixDot extends CharProperty {
4181         boolean isSatisfiedBy(int ch) {
4182             return ch != '\n';
4183         }
4184     }
4185 
4186     /**
4187      * The 0 or 1 quantifier. This one class implements all three types.
4188      */
4189     static final class Ques extends Node {
4190         Node atom;
4191         int type;
4192         Ques(Node node, int type) {
4193             this.atom = node;
4194             this.type = type;
4195         }
4196         boolean match(Matcher matcher, int i, CharSequence seq) {
4197             switch (type) {
4198             case GREEDY:
4199                 return (atom.match(matcher, i, seq) && next.match(matcher, matcher.last, seq))
4200                     || next.match(matcher, i, seq);
4201             case LAZY:
4202                 return next.match(matcher, i, seq)
4203                     || (atom.match(matcher, i, seq) && next.match(matcher, matcher.last, seq));
4204             case POSSESSIVE:
4205                 if (atom.match(matcher, i, seq)) i = matcher.last;
4206                 return next.match(matcher, i, seq);
4207             default:
4208                 return atom.match(matcher, i, seq) && next.match(matcher, matcher.last, seq);
4209             }
4210         }
4211         boolean study(TreeInfo info) {
4212             if (type != INDEPENDENT) {
4213                 int minL = info.minLength;
4214                 atom.study(info);
4215                 info.minLength = minL;
4216                 info.deterministic = false;
4217                 return next.study(info);
4218             } else {
4219                 atom.study(info);
4220                 return next.study(info);
4221             }
4222         }
4223     }
4224 
4225     /**
4226      * Handles the curly-brace style repetition with a specified minimum and
4227      * maximum occurrences. The * quantifier is handled as a special case.
4228      * This class handles the three types.
4229      */
4230     static final class Curly extends Node {
4231         Node atom;
4232         int type;
4233         int cmin;
4234         int cmax;
4235 
4236         Curly(Node node, int cmin, int cmax, int type) {
4237             this.atom = node;
4238             this.type = type;
4239             this.cmin = cmin;
4240             this.cmax = cmax;
4241         }
4242         boolean match(Matcher matcher, int i, CharSequence seq) {
4243             int j;
4244             for (j = 0; j < cmin; j++) {
4245                 if (atom.match(matcher, i, seq)) {
4246                     i = matcher.last;
4247                     continue;
4248                 }
4249                 return false;
4250             }
4251             if (type == GREEDY)
4252                 return match0(matcher, i, j, seq);
4253             else if (type == LAZY)
4254                 return match1(matcher, i, j, seq);
4255             else
4256                 return match2(matcher, i, j, seq);
4257         }
4258         // Greedy match.
4259         // i is the index to start matching at
4260         // j is the number of atoms that have matched
4261         boolean match0(Matcher matcher, int i, int j, CharSequence seq) {
4262             if (j >= cmax) {
4263                 // We have matched the maximum... continue with the rest of
4264                 // the regular expression
4265                 return next.match(matcher, i, seq);
4266             }
4267             int backLimit = j;
4268             while (atom.match(matcher, i, seq)) {
4269                 // k is the length of this match
4270                 int k = matcher.last - i;
4271                 if (k == 0) // Zero length match
4272                     break;
4273                 // Move up index and number matched
4274                 i = matcher.last;
4275                 j++;
4276                 // We are greedy so match as many as we can
4277                 while (j < cmax) {
4278                     if (!atom.match(matcher, i, seq))
4279                         break;
4280                     if (i + k != matcher.last) {
4281                         if (match0(matcher, matcher.last, j+1, seq))
4282                             return true;
4283                         break;
4284                     }
4285                     i += k;
4286                     j++;
4287                 }
4288                 // Handle backing off if match fails
4289                 while (j >= backLimit) {
4290                    if (next.match(matcher, i, seq))
4291                         return true;
4292                     i -= k;
4293                     j--;
4294                 }
4295                 return false;
4296             }
4297             return next.match(matcher, i, seq);
4298         }
4299         // Reluctant match. At this point, the minimum has been satisfied.
4300         // i is the index to start matching at
4301         // j is the number of atoms that have matched
4302         boolean match1(Matcher matcher, int i, int j, CharSequence seq) {
4303             for (;;) {
4304                 // Try finishing match without consuming any more
4305                 if (next.match(matcher, i, seq))
4306                     return true;
4307                 // At the maximum, no match found
4308                 if (j >= cmax)
4309                     return false;
4310                 // Okay, must try one more atom
4311                 if (!atom.match(matcher, i, seq))
4312                     return false;
4313                 // If we haven't moved forward then must break out
4314                 if (i == matcher.last)
4315                     return false;
4316                 // Move up index and number matched
4317                 i = matcher.last;
4318                 j++;
4319             }
4320         }
4321         boolean match2(Matcher matcher, int i, int j, CharSequence seq) {
4322             for (; j < cmax; j++) {
4323                 if (!atom.match(matcher, i, seq))
4324                     break;
4325                 if (i == matcher.last)
4326                     break;
4327                 i = matcher.last;
4328             }
4329             return next.match(matcher, i, seq);
4330         }
4331         boolean study(TreeInfo info) {
4332             // Save original info
4333             int minL = info.minLength;
4334             int maxL = info.maxLength;
4335             boolean maxV = info.maxValid;
4336             boolean detm = info.deterministic;
4337             info.reset();
4338 
4339             atom.study(info);
4340 
4341             int temp = info.minLength * cmin + minL;
4342             if (temp < minL) {
4343                 temp = 0xFFFFFFF; // arbitrary large number
4344             }
4345             info.minLength = temp;
4346 
4347             if (maxV & info.maxValid) {
4348                 temp = info.maxLength * cmax + maxL;
4349                 info.maxLength = temp;
4350                 if (temp < maxL) {
4351                     info.maxValid = false;
4352                 }
4353             } else {
4354                 info.maxValid = false;
4355             }
4356 
4357             if (info.deterministic && cmin == cmax)
4358                 info.deterministic = detm;
4359             else
4360                 info.deterministic = false;
4361             return next.study(info);
4362         }
4363     }
4364 
4365     /**
4366      * Handles the curly-brace style repetition with a specified minimum and
4367      * maximum occurrences in deterministic cases. This is an iterative
4368      * optimization over the Prolog and Loop system which would handle this
4369      * in a recursive way. The * quantifier is handled as a special case.
4370      * If capture is true then this class saves group settings and ensures
4371      * that groups are unset when backing off of a group match.
4372      */
4373     static final class GroupCurly extends Node {
4374         Node atom;
4375         int type;
4376         int cmin;
4377         int cmax;
4378         int localIndex;
4379         int groupIndex;
4380         boolean capture;
4381 
4382         GroupCurly(Node node, int cmin, int cmax, int type, int local,
4383                    int group, boolean capture) {
4384             this.atom = node;
4385             this.type = type;
4386             this.cmin = cmin;
4387             this.cmax = cmax;
4388             this.localIndex = local;
4389             this.groupIndex = group;
4390             this.capture = capture;
4391         }
4392         boolean match(Matcher matcher, int i, CharSequence seq) {
4393             int[] groups = matcher.groups;
4394             int[] locals = matcher.locals;
4395             int save0 = locals[localIndex];
4396             int save1 = 0;
4397             int save2 = 0;
4398 
4399             if (capture) {
4400                 save1 = groups[groupIndex];
4401                 save2 = groups[groupIndex+1];
4402             }
4403 
4404             // Notify GroupTail there is no need to setup group info
4405             // because it will be set here
4406             locals[localIndex] = -1;
4407 
4408             boolean ret = true;
4409             for (int j = 0; j < cmin; j++) {
4410                 if (atom.match(matcher, i, seq)) {
4411                     if (capture) {
4412                         groups[groupIndex] = i;
4413                         groups[groupIndex+1] = matcher.last;
4414                     }
4415                     i = matcher.last;
4416                 } else {
4417                     ret = false;
4418                     break;
4419                 }
4420             }
4421             if (ret) {
4422                 if (type == GREEDY) {
4423                     ret = match0(matcher, i, cmin, seq);
4424                 } else if (type == LAZY) {
4425                     ret = match1(matcher, i, cmin, seq);
4426                 } else {
4427                     ret = match2(matcher, i, cmin, seq);
4428                 }
4429             }
4430             if (!ret) {
4431                 locals[localIndex] = save0;
4432                 if (capture) {
4433                     groups[groupIndex] = save1;
4434                     groups[groupIndex+1] = save2;
4435                 }
4436             }
4437             return ret;
4438         }
4439         // Aggressive group match
4440         boolean match0(Matcher matcher, int i, int j, CharSequence seq) {
4441             // don't back off passing the starting "j"
4442             int min = j;
4443             int[] groups = matcher.groups;
4444             int save0 = 0;
4445             int save1 = 0;
4446             if (capture) {
4447                 save0 = groups[groupIndex];
4448                 save1 = groups[groupIndex+1];
4449             }
4450             for (;;) {
4451                 if (j >= cmax)
4452                     break;
4453                 if (!atom.match(matcher, i, seq))
4454                     break;
4455                 int k = matcher.last - i;
4456                 if (k <= 0) {
4457                     if (capture) {
4458                         groups[groupIndex] = i;
4459                         groups[groupIndex+1] = i + k;
4460                     }
4461                     i = i + k;
4462                     break;
4463                 }
4464                 for (;;) {
4465                     if (capture) {
4466                         groups[groupIndex] = i;
4467                         groups[groupIndex+1] = i + k;
4468                     }
4469                     i = i + k;
4470                     if (++j >= cmax)
4471                         break;
4472                     if (!atom.match(matcher, i, seq))
4473                         break;
4474                     if (i + k != matcher.last) {
4475                         if (match0(matcher, i, j, seq))
4476                             return true;
4477                         break;
4478                     }
4479                 }
4480                 while (j > min) {
4481                     if (next.match(matcher, i, seq)) {
4482                         if (capture) {
4483                             groups[groupIndex+1] = i;
4484                             groups[groupIndex] = i - k;
4485                         }
4486                         return true;
4487                     }
4488                     // backing off
4489                     i = i - k;
4490                     if (capture) {
4491                         groups[groupIndex+1] = i;
4492                         groups[groupIndex] = i - k;
4493                     }
4494                     j--;
4495 
4496                 }
4497                 break;
4498             }
4499             if (capture) {
4500                 groups[groupIndex] = save0;
4501                 groups[groupIndex+1] = save1;
4502             }
4503             return next.match(matcher, i, seq);
4504         }
4505         // Reluctant matching
4506         boolean match1(Matcher matcher, int i, int j, CharSequence seq) {
4507             for (;;) {
4508                 if (next.match(matcher, i, seq))
4509                     return true;
4510                 if (j >= cmax)
4511                     return false;
4512                 if (!atom.match(matcher, i, seq))
4513                     return false;
4514                 if (i == matcher.last)
4515                     return false;
4516                 if (capture) {
4517                     matcher.groups[groupIndex] = i;
4518                     matcher.groups[groupIndex+1] = matcher.last;
4519                 }
4520                 i = matcher.last;
4521                 j++;
4522             }
4523         }
4524         // Possessive matching
4525         boolean match2(Matcher matcher, int i, int j, CharSequence seq) {
4526             for (; j < cmax; j++) {
4527                 if (!atom.match(matcher, i, seq)) {
4528                     break;
4529                 }
4530                 if (capture) {
4531                     matcher.groups[groupIndex] = i;
4532                     matcher.groups[groupIndex+1] = matcher.last;
4533                 }
4534                 if (i == matcher.last) {
4535                     break;
4536                 }
4537                 i = matcher.last;
4538             }
4539             return next.match(matcher, i, seq);
4540         }
4541         boolean study(TreeInfo info) {
4542             // Save original info
4543             int minL = info.minLength;
4544             int maxL = info.maxLength;
4545             boolean maxV = info.maxValid;
4546             boolean detm = info.deterministic;
4547             info.reset();
4548 
4549             atom.study(info);
4550 
4551             int temp = info.minLength * cmin + minL;
4552             if (temp < minL) {
4553                 temp = 0xFFFFFFF; // Arbitrary large number
4554             }
4555             info.minLength = temp;
4556 
4557             if (maxV & info.maxValid) {
4558                 temp = info.maxLength * cmax + maxL;
4559                 info.maxLength = temp;
4560                 if (temp < maxL) {
4561                     info.maxValid = false;
4562                 }
4563             } else {
4564                 info.maxValid = false;
4565             }
4566 
4567             if (info.deterministic && cmin == cmax) {
4568                 info.deterministic = detm;
4569             } else {
4570                 info.deterministic = false;
4571             }
4572             return next.study(info);
4573         }
4574     }
4575 
4576     /**
4577      * A Guard node at the end of each atom node in a Branch. It
4578      * serves the purpose of chaining the "match" operation to
4579      * "next" but not the "study", so we can collect the TreeInfo
4580      * of each atom node without including the TreeInfo of the
4581      * "next".
4582      */
4583     static final class BranchConn extends Node {
4584         BranchConn() {};
4585         boolean match(Matcher matcher, int i, CharSequence seq) {
4586             return next.match(matcher, i, seq);
4587         }
4588         boolean study(TreeInfo info) {
4589             return info.deterministic;
4590         }
4591     }
4592 
4593     /**
4594      * Handles the branching of alternations. Note this is also used for
4595      * the ? quantifier to branch between the case where it matches once
4596      * and where it does not occur.
4597      */
4598     static final class Branch extends Node {
4599         Node[] atoms = new Node[2];
4600         int size = 2;
4601         Node conn;
4602         Branch(Node first, Node second, Node branchConn) {
4603             conn = branchConn;
4604             atoms[0] = first;
4605             atoms[1] = second;
4606         }
4607 
4608         void add(Node node) {
4609             if (size >= atoms.length) {
4610                 Node[] tmp = new Node[atoms.length*2];
4611                 System.arraycopy(atoms, 0, tmp, 0, atoms.length);
4612                 atoms = tmp;
4613             }
4614             atoms[size++] = node;
4615         }
4616 
4617         boolean match(Matcher matcher, int i, CharSequence seq) {
4618             for (int n = 0; n < size; n++) {
4619                 if (atoms[n] == null) {
4620                     if (conn.next.match(matcher, i, seq))
4621                         return true;
4622                 } else if (atoms[n].match(matcher, i, seq)) {
4623                     return true;
4624                 }
4625             }
4626             return false;
4627         }
4628 
4629         boolean study(TreeInfo info) {
4630             int minL = info.minLength;
4631             int maxL = info.maxLength;
4632             boolean maxV = info.maxValid;
4633 
4634             int minL2 = Integer.MAX_VALUE; //arbitrary large enough num
4635             int maxL2 = -1;
4636             for (int n = 0; n < size; n++) {
4637                 info.reset();
4638                 if (atoms[n] != null)
4639                     atoms[n].study(info);
4640                 minL2 = Math.min(minL2, info.minLength);
4641                 maxL2 = Math.max(maxL2, info.maxLength);
4642                 maxV = (maxV & info.maxValid);
4643             }
4644 
4645             minL += minL2;
4646             maxL += maxL2;
4647 
4648             info.reset();
4649             conn.next.study(info);
4650 
4651             info.minLength += minL;
4652             info.maxLength += maxL;
4653             info.maxValid &= maxV;
4654             info.deterministic = false;
4655             return false;
4656         }
4657     }
4658 
4659     /**
4660      * The GroupHead saves the location where the group begins in the locals
4661      * and restores them when the match is done.
4662      *
4663      * The matchRef is used when a reference to this group is accessed later
4664      * in the expression. The locals will have a negative value in them to
4665      * indicate that we do not want to unset the group if the reference
4666      * doesn't match.
4667      */
4668     static final class GroupHead extends Node {
4669         int localIndex;
4670         GroupHead(int localCount) {
4671             localIndex = localCount;
4672         }
4673         boolean match(Matcher matcher, int i, CharSequence seq) {
4674             int save = matcher.locals[localIndex];
4675             matcher.locals[localIndex] = i;
4676             boolean ret = next.match(matcher, i, seq);
4677             matcher.locals[localIndex] = save;
4678             return ret;
4679         }
4680         boolean matchRef(Matcher matcher, int i, CharSequence seq) {
4681             int save = matcher.locals[localIndex];
4682             matcher.locals[localIndex] = ~i; // HACK
4683             boolean ret = next.match(matcher, i, seq);
4684             matcher.locals[localIndex] = save;
4685             return ret;
4686         }
4687     }
4688 
4689     /**
4690      * Recursive reference to a group in the regular expression. It calls
4691      * matchRef because if the reference fails to match we would not unset
4692      * the group.
4693      */
4694     static final class GroupRef extends Node {
4695         GroupHead head;
4696         GroupRef(GroupHead head) {
4697             this.head = head;
4698         }
4699         boolean match(Matcher matcher, int i, CharSequence seq) {
4700             return head.matchRef(matcher, i, seq)
4701                 && next.match(matcher, matcher.last, seq);
4702         }
4703         boolean study(TreeInfo info) {
4704             info.maxValid = false;
4705             info.deterministic = false;
4706             return next.study(info);
4707         }
4708     }
4709 
4710     /**
4711      * The GroupTail handles the setting of group beginning and ending
4712      * locations when groups are successfully matched. It must also be able to
4713      * unset groups that have to be backed off of.
4714      *
4715      * The GroupTail node is also used when a previous group is referenced,
4716      * and in that case no group information needs to be set.
4717      */
4718     static final class GroupTail extends Node {
4719         int localIndex;
4720         int groupIndex;
4721         GroupTail(int localCount, int groupCount) {
4722             localIndex = localCount;
4723             groupIndex = groupCount + groupCount;
4724         }
4725         boolean match(Matcher matcher, int i, CharSequence seq) {
4726             int tmp = matcher.locals[localIndex];
4727             if (tmp >= 0) { // This is the normal group case.
4728                 // Save the group so we can unset it if it
4729                 // backs off of a match.
4730                 int groupStart = matcher.groups[groupIndex];
4731                 int groupEnd = matcher.groups[groupIndex+1];
4732 
4733                 matcher.groups[groupIndex] = tmp;
4734                 matcher.groups[groupIndex+1] = i;
4735                 if (next.match(matcher, i, seq)) {
4736                     return true;
4737                 }
4738                 matcher.groups[groupIndex] = groupStart;
4739                 matcher.groups[groupIndex+1] = groupEnd;
4740                 return false;
4741             } else {
4742                 // This is a group reference case. We don't need to save any
4743                 // group info because it isn't really a group.
4744                 matcher.last = i;
4745                 return true;
4746             }
4747         }
4748     }
4749 
4750     /**
4751      * This sets up a loop to handle a recursive quantifier structure.
4752      */
4753     static final class Prolog extends Node {
4754         Loop loop;
4755         Prolog(Loop loop) {
4756             this.loop = loop;
4757         }
4758         boolean match(Matcher matcher, int i, CharSequence seq) {
4759             return loop.matchInit(matcher, i, seq);
4760         }
4761         boolean study(TreeInfo info) {
4762             return loop.study(info);
4763         }
4764     }
4765 
4766     /**
4767      * Handles the repetition count for a greedy Curly. The matchInit
4768      * is called from the Prolog to save the index of where the group
4769      * beginning is stored. A zero length group check occurs in the
4770      * normal match but is skipped in the matchInit.
4771      */
4772     static class Loop extends Node {
4773         Node body;
4774         int countIndex; // local count index in matcher locals
4775         int beginIndex; // group beginning index
4776         int cmin, cmax;
4777         Loop(int countIndex, int beginIndex) {
4778             this.countIndex = countIndex;
4779             this.beginIndex = beginIndex;
4780         }
4781         boolean match(Matcher matcher, int i, CharSequence seq) {
4782             // Avoid infinite loop in zero-length case.
4783             if (i > matcher.locals[beginIndex]) {
4784                 int count = matcher.locals[countIndex];
4785 
4786                 // This block is for before we reach the minimum
4787                 // iterations required for the loop to match
4788                 if (count < cmin) {
4789                     matcher.locals[countIndex] = count + 1;
4790                     boolean b = body.match(matcher, i, seq);
4791                     // If match failed we must backtrack, so
4792                     // the loop count should NOT be incremented
4793                     if (!b)
4794                         matcher.locals[countIndex] = count;
4795                     // Return success or failure since we are under
4796                     // minimum
4797                     return b;
4798                 }
4799                 // This block is for after we have the minimum
4800                 // iterations required for the loop to match
4801                 if (count < cmax) {
4802                     matcher.locals[countIndex] = count + 1;
4803                     boolean b = body.match(matcher, i, seq);
4804                     // If match failed we must backtrack, so
4805                     // the loop count should NOT be incremented
4806                     if (!b)
4807                         matcher.locals[countIndex] = count;
4808                     else
4809                         return true;
4810                 }
4811             }
4812             return next.match(matcher, i, seq);
4813         }
4814         boolean matchInit(Matcher matcher, int i, CharSequence seq) {
4815             int save = matcher.locals[countIndex];
4816             boolean ret = false;
4817             if (0 < cmin) {
4818                 matcher.locals[countIndex] = 1;
4819                 ret = body.match(matcher, i, seq);
4820             } else if (0 < cmax) {
4821                 matcher.locals[countIndex] = 1;
4822                 ret = body.match(matcher, i, seq);
4823                 if (ret == false)
4824                     ret = next.match(matcher, i, seq);
4825             } else {
4826                 ret = next.match(matcher, i, seq);
4827             }
4828             matcher.locals[countIndex] = save;
4829             return ret;
4830         }
4831         boolean study(TreeInfo info) {
4832             info.maxValid = false;
4833             info.deterministic = false;
4834             return false;
4835         }
4836     }
4837 
4838     /**
4839      * Handles the repetition count for a reluctant Curly. The matchInit
4840      * is called from the Prolog to save the index of where the group
4841      * beginning is stored. A zero length group check occurs in the
4842      * normal match but is skipped in the matchInit.
4843      */
4844     static final class LazyLoop extends Loop {
4845         LazyLoop(int countIndex, int beginIndex) {
4846             super(countIndex, beginIndex);
4847         }
4848         boolean match(Matcher matcher, int i, CharSequence seq) {
4849             // Check for zero length group
4850             if (i > matcher.locals[beginIndex]) {
4851                 int count = matcher.locals[countIndex];
4852                 if (count < cmin) {
4853                     matcher.locals[countIndex] = count + 1;
4854                     boolean result = body.match(matcher, i, seq);
4855                     // If match failed we must backtrack, so
4856                     // the loop count should NOT be incremented
4857                     if (!result)
4858                         matcher.locals[countIndex] = count;
4859                     return result;
4860                 }
4861                 if (next.match(matcher, i, seq))
4862                     return true;
4863                 if (count < cmax) {
4864                     matcher.locals[countIndex] = count + 1;
4865                     boolean result = body.match(matcher, i, seq);
4866                     // If match failed we must backtrack, so
4867                     // the loop count should NOT be incremented
4868                     if (!result)
4869                         matcher.locals[countIndex] = count;
4870                     return result;
4871                 }
4872                 return false;
4873             }
4874             return next.match(matcher, i, seq);
4875         }
4876         boolean matchInit(Matcher matcher, int i, CharSequence seq) {
4877             int save = matcher.locals[countIndex];
4878             boolean ret = false;
4879             if (0 < cmin) {
4880                 matcher.locals[countIndex] = 1;
4881                 ret = body.match(matcher, i, seq);
4882             } else if (next.match(matcher, i, seq)) {
4883                 ret = true;
4884             } else if (0 < cmax) {
4885                 matcher.locals[countIndex] = 1;
4886                 ret = body.match(matcher, i, seq);
4887             }
4888             matcher.locals[countIndex] = save;
4889             return ret;
4890         }
4891         boolean study(TreeInfo info) {
4892             info.maxValid = false;
4893             info.deterministic = false;
4894             return false;
4895         }
4896     }
4897 
4898     /**
4899      * Refers to a group in the regular expression. Attempts to match
4900      * whatever the group referred to last matched.
4901      */
4902     static class BackRef extends Node {
4903         int groupIndex;
4904         BackRef(int groupCount) {
4905             super();
4906             groupIndex = groupCount + groupCount;
4907         }
4908         boolean match(Matcher matcher, int i, CharSequence seq) {
4909             int j = matcher.groups[groupIndex];
4910             int k = matcher.groups[groupIndex+1];
4911 
4912             int groupSize = k - j;
4913             // If the referenced group didn't match, neither can this
4914             if (j < 0)
4915                 return false;
4916 
4917             // If there isn't enough input left no match
4918             if (i + groupSize > matcher.to) {
4919                 matcher.hitEnd = true;
4920                 return false;
4921             }
4922             // Check each new char to make sure it matches what the group
4923             // referenced matched last time around
4924             for (int index=0; index<groupSize; index++)
4925                 if (seq.charAt(i+index) != seq.charAt(j+index))
4926                     return false;
4927 
4928             return next.match(matcher, i+groupSize, seq);
4929         }
4930         boolean study(TreeInfo info) {
4931             info.maxValid = false;
4932             return next.study(info);
4933         }
4934     }
4935 
4936     static class CIBackRef extends Node {
4937         int groupIndex;
4938         boolean doUnicodeCase;
4939         CIBackRef(int groupCount, boolean doUnicodeCase) {
4940             super();
4941             groupIndex = groupCount + groupCount;
4942             this.doUnicodeCase = doUnicodeCase;
4943         }
4944         boolean match(Matcher matcher, int i, CharSequence seq) {
4945             int j = matcher.groups[groupIndex];
4946             int k = matcher.groups[groupIndex+1];
4947 
4948             int groupSize = k - j;
4949 
4950             // If the referenced group didn't match, neither can this
4951             if (j < 0)
4952                 return false;
4953 
4954             // If there isn't enough input left no match
4955             if (i + groupSize > matcher.to) {
4956                 matcher.hitEnd = true;
4957                 return false;
4958             }
4959 
4960             // Check each new char to make sure it matches what the group
4961             // referenced matched last time around
4962             int x = i;
4963             for (int index=0; index<groupSize; index++) {
4964                 int c1 = Character.codePointAt(seq, x);
4965                 int c2 = Character.codePointAt(seq, j);
4966                 if (c1 != c2) {
4967                     if (doUnicodeCase) {
4968                         int cc1 = Character.toUpperCase(c1);
4969                         int cc2 = Character.toUpperCase(c2);
4970                         if (cc1 != cc2 &&
4971                             Character.toLowerCase(cc1) !=
4972                             Character.toLowerCase(cc2))
4973                             return false;
4974                     } else {
4975                         if (ASCII.toLower(c1) != ASCII.toLower(c2))
4976                             return false;
4977                     }
4978                 }
4979                 x += Character.charCount(c1);
4980                 j += Character.charCount(c2);
4981             }
4982 
4983             return next.match(matcher, i+groupSize, seq);
4984         }
4985         boolean study(TreeInfo info) {
4986             info.maxValid = false;
4987             return next.study(info);
4988         }
4989     }
4990 
4991     /**
4992      * Searches until the next instance of its atom. This is useful for
4993      * finding the atom efficiently without passing an instance of it
4994      * (greedy problem) and without a lot of wasted search time (reluctant
4995      * problem).
4996      */
4997     static final class First extends Node {
4998         Node atom;
4999         First(Node node) {
5000             this.atom = BnM.optimize(node);
5001         }
5002         boolean match(Matcher matcher, int i, CharSequence seq) {
5003             if (atom instanceof BnM) {
5004                 return atom.match(matcher, i, seq)
5005                     && next.match(matcher, matcher.last, seq);
5006             }
5007             for (;;) {
5008                 if (i > matcher.to) {
5009                     matcher.hitEnd = true;
5010                     return false;
5011                 }
5012                 if (atom.match(matcher, i, seq)) {
5013                     return next.match(matcher, matcher.last, seq);
5014                 }
5015                 i += countChars(seq, i, 1);
5016                 matcher.first++;
5017             }
5018         }
5019         boolean study(TreeInfo info) {
5020             atom.study(info);
5021             info.maxValid = false;
5022             info.deterministic = false;
5023             return next.study(info);
5024         }
5025     }
5026 
5027     static final class Conditional extends Node {
5028         Node cond, yes, not;
5029         Conditional(Node cond, Node yes, Node not) {
5030             this.cond = cond;
5031             this.yes = yes;
5032             this.not = not;
5033         }
5034         boolean match(Matcher matcher, int i, CharSequence seq) {
5035             if (cond.match(matcher, i, seq)) {
5036                 return yes.match(matcher, i, seq);
5037             } else {
5038                 return not.match(matcher, i, seq);
5039             }
5040         }
5041         boolean study(TreeInfo info) {
5042             int minL = info.minLength;
5043             int maxL = info.maxLength;
5044             boolean maxV = info.maxValid;
5045             info.reset();
5046             yes.study(info);
5047 
5048             int minL2 = info.minLength;
5049             int maxL2 = info.maxLength;
5050             boolean maxV2 = info.maxValid;
5051             info.reset();
5052             not.study(info);
5053 
5054             info.minLength = minL + Math.min(minL2, info.minLength);
5055             info.maxLength = maxL + Math.max(maxL2, info.maxLength);
5056             info.maxValid = (maxV & maxV2 & info.maxValid);
5057             info.deterministic = false;
5058             return next.study(info);
5059         }
5060     }
5061 
5062     /**
5063      * Zero width positive lookahead.
5064      */
5065     static final class Pos extends Node {
5066         Node cond;
5067         Pos(Node cond) {
5068             this.cond = cond;
5069         }
5070         boolean match(Matcher matcher, int i, CharSequence seq) {
5071             int savedTo = matcher.to;
5072             boolean conditionMatched = false;
5073 
5074             // Relax transparent region boundaries for lookahead
5075             if (matcher.transparentBounds)
5076                 matcher.to = matcher.getTextLength();
5077             try {
5078                 conditionMatched = cond.match(matcher, i, seq);
5079             } finally {
5080                 // Reinstate region boundaries
5081                 matcher.to = savedTo;
5082             }
5083             return conditionMatched && next.match(matcher, i, seq);
5084         }
5085     }
5086 
5087     /**
5088      * Zero width negative lookahead.
5089      */
5090     static final class Neg extends Node {
5091         Node cond;
5092         Neg(Node cond) {
5093             this.cond = cond;
5094         }
5095         boolean match(Matcher matcher, int i, CharSequence seq) {
5096             int savedTo = matcher.to;
5097             boolean conditionMatched = false;
5098 
5099             // Relax transparent region boundaries for lookahead
5100             if (matcher.transparentBounds)
5101                 matcher.to = matcher.getTextLength();
5102             try {
5103                 if (i < matcher.to) {
5104                     conditionMatched = !cond.match(matcher, i, seq);
5105                 } else {
5106                     // If a negative lookahead succeeds then more input
5107                     // could cause it to fail!
5108                     matcher.requireEnd = true;
5109                     conditionMatched = !cond.match(matcher, i, seq);
5110                 }
5111             } finally {
5112                 // Reinstate region boundaries
5113                 matcher.to = savedTo;
5114             }
5115             return conditionMatched && next.match(matcher, i, seq);
5116         }
5117     }
5118 
5119     /**
5120      * For use with lookbehinds; matches the position where the lookbehind
5121      * was encountered.
5122      */
5123     static Node lookbehindEnd = new Node() {
5124         boolean match(Matcher matcher, int i, CharSequence seq) {
5125             return i == matcher.lookbehindTo;
5126         }
5127     };
5128 
5129     /**
5130      * Zero width positive lookbehind.
5131      */
5132     static class Behind extends Node {
5133         Node cond;
5134         int rmax, rmin;
5135         Behind(Node cond, int rmax, int rmin) {
5136             this.cond = cond;
5137             this.rmax = rmax;
5138             this.rmin = rmin;
5139         }
5140 
5141         boolean match(Matcher matcher, int i, CharSequence seq) {
5142             int savedFrom = matcher.from;
5143             boolean conditionMatched = false;
5144             int startIndex = (!matcher.transparentBounds) ?
5145                              matcher.from : 0;
5146             int from = Math.max(i - rmax, startIndex);
5147             // Set end boundary
5148             int savedLBT = matcher.lookbehindTo;
5149             matcher.lookbehindTo = i;
5150             // Relax transparent region boundaries for lookbehind
5151             if (matcher.transparentBounds)
5152                 matcher.from = 0;
5153             for (int j = i - rmin; !conditionMatched && j >= from; j--) {
5154                 conditionMatched = cond.match(matcher, j, seq);
5155             }
5156             matcher.from = savedFrom;
5157             matcher.lookbehindTo = savedLBT;
5158             return conditionMatched && next.match(matcher, i, seq);
5159         }
5160     }
5161 
5162     /**
5163      * Zero width positive lookbehind, including supplementary
5164      * characters or unpaired surrogates.
5165      */
5166     static final class BehindS extends Behind {
5167         BehindS(Node cond, int rmax, int rmin) {
5168             super(cond, rmax, rmin);
5169         }
5170         boolean match(Matcher matcher, int i, CharSequence seq) {
5171             int rmaxChars = countChars(seq, i, -rmax);
5172             int rminChars = countChars(seq, i, -rmin);
5173             int savedFrom = matcher.from;
5174             int startIndex = (!matcher.transparentBounds) ?
5175                              matcher.from : 0;
5176             boolean conditionMatched = false;
5177             int from = Math.max(i - rmaxChars, startIndex);
5178             // Set end boundary
5179             int savedLBT = matcher.lookbehindTo;
5180             matcher.lookbehindTo = i;
5181             // Relax transparent region boundaries for lookbehind
5182             if (matcher.transparentBounds)
5183                 matcher.from = 0;
5184 
5185             for (int j = i - rminChars;
5186                  !conditionMatched && j >= from;
5187                  j -= j>from ? countChars(seq, j, -1) : 1) {
5188                 conditionMatched = cond.match(matcher, j, seq);
5189             }
5190             matcher.from = savedFrom;
5191             matcher.lookbehindTo = savedLBT;
5192             return conditionMatched && next.match(matcher, i, seq);
5193         }
5194     }
5195 
5196     /**
5197      * Zero width negative lookbehind.
5198      */
5199     static class NotBehind extends Node {
5200         Node cond;
5201         int rmax, rmin;
5202         NotBehind(Node cond, int rmax, int rmin) {
5203             this.cond = cond;
5204             this.rmax = rmax;
5205             this.rmin = rmin;
5206         }
5207 
5208         boolean match(Matcher matcher, int i, CharSequence seq) {
5209             int savedLBT = matcher.lookbehindTo;
5210             int savedFrom = matcher.from;
5211             boolean conditionMatched = false;
5212             int startIndex = (!matcher.transparentBounds) ?
5213                              matcher.from : 0;
5214             int from = Math.max(i - rmax, startIndex);
5215             matcher.lookbehindTo = i;
5216             // Relax transparent region boundaries for lookbehind
5217             if (matcher.transparentBounds)
5218                 matcher.from = 0;
5219             for (int j = i - rmin; !conditionMatched && j >= from; j--) {
5220                 conditionMatched = cond.match(matcher, j, seq);
5221             }
5222             // Reinstate region boundaries
5223             matcher.from = savedFrom;
5224             matcher.lookbehindTo = savedLBT;
5225             return !conditionMatched && next.match(matcher, i, seq);
5226         }
5227     }
5228 
5229     /**
5230      * Zero width negative lookbehind, including supplementary
5231      * characters or unpaired surrogates.
5232      */
5233     static final class NotBehindS extends NotBehind {
5234         NotBehindS(Node cond, int rmax, int rmin) {
5235             super(cond, rmax, rmin);
5236         }
5237         boolean match(Matcher matcher, int i, CharSequence seq) {
5238             int rmaxChars = countChars(seq, i, -rmax);
5239             int rminChars = countChars(seq, i, -rmin);
5240             int savedFrom = matcher.from;
5241             int savedLBT = matcher.lookbehindTo;
5242             boolean conditionMatched = false;
5243             int startIndex = (!matcher.transparentBounds) ?
5244                              matcher.from : 0;
5245             int from = Math.max(i - rmaxChars, startIndex);
5246             matcher.lookbehindTo = i;
5247             // Relax transparent region boundaries for lookbehind
5248             if (matcher.transparentBounds)
5249                 matcher.from = 0;
5250             for (int j = i - rminChars;
5251                  !conditionMatched && j >= from;
5252                  j -= j>from ? countChars(seq, j, -1) : 1) {
5253                 conditionMatched = cond.match(matcher, j, seq);
5254             }
5255             //Reinstate region boundaries
5256             matcher.from = savedFrom;
5257             matcher.lookbehindTo = savedLBT;
5258             return !conditionMatched && next.match(matcher, i, seq);
5259         }
5260     }
5261 
5262     /**
5263      * Returns the set union of two CharProperty nodes.
5264      */
5265     private static CharProperty union(final CharProperty lhs,
5266                                       final CharProperty rhs) {
5267         return new CharProperty() {
5268                 boolean isSatisfiedBy(int ch) {
5269                     return lhs.isSatisfiedBy(ch) || rhs.isSatisfiedBy(ch);}};
5270     }
5271 
5272     /**
5273      * Returns the set intersection of two CharProperty nodes.
5274      */
5275     private static CharProperty intersection(final CharProperty lhs,
5276                                              final CharProperty rhs) {
5277         return new CharProperty() {
5278                 boolean isSatisfiedBy(int ch) {
5279                     return lhs.isSatisfiedBy(ch) && rhs.isSatisfiedBy(ch);}};
5280     }
5281 
5282     /**
5283      * Returns the set difference of two CharProperty nodes.
5284      */
5285     private static CharProperty setDifference(final CharProperty lhs,
5286                                               final CharProperty rhs) {
5287         return new CharProperty() {
5288                 boolean isSatisfiedBy(int ch) {
5289                     return ! rhs.isSatisfiedBy(ch) && lhs.isSatisfiedBy(ch);}};
5290     }
5291 
5292     /**
5293      * Handles word boundaries. Includes a field to allow this one class to
5294      * deal with the different types of word boundaries we can match. The word
5295      * characters include underscores, letters, and digits. Non spacing marks
5296      * can are also part of a word if they have a base character, otherwise
5297      * they are ignored for purposes of finding word boundaries.
5298      */
5299     static final class Bound extends Node {
5300         static int LEFT = 0x1;
5301         static int RIGHT= 0x2;
5302         static int BOTH = 0x3;
5303         static int NONE = 0x4;
5304         int type;
5305         boolean useUWORD;
5306         Bound(int n, boolean useUWORD) {
5307             type = n;
5308             this.useUWORD = useUWORD;
5309         }
5310 
5311         boolean isWord(int ch) {
5312             return useUWORD ? UnicodeProp.WORD.is(ch)
5313                             : (ch == '_' || Character.isLetterOrDigit(ch));
5314         }
5315 
5316         int check(Matcher matcher, int i, CharSequence seq) {
5317             int ch;
5318             boolean left = false;
5319             int startIndex = matcher.from;
5320             int endIndex = matcher.to;
5321             if (matcher.transparentBounds) {
5322                 startIndex = 0;
5323                 endIndex = matcher.getTextLength();
5324             }
5325             if (i > startIndex) {
5326                 ch = Character.codePointBefore(seq, i);
5327                 left = (isWord(ch) ||
5328                     ((Character.getType(ch) == Character.NON_SPACING_MARK)
5329                      && hasBaseCharacter(matcher, i-1, seq)));
5330             }
5331             boolean right = false;
5332             if (i < endIndex) {
5333                 ch = Character.codePointAt(seq, i);
5334                 right = (isWord(ch) ||
5335                     ((Character.getType(ch) == Character.NON_SPACING_MARK)
5336                      && hasBaseCharacter(matcher, i, seq)));
5337             } else {
5338                 // Tried to access char past the end
5339                 matcher.hitEnd = true;
5340                 // The addition of another char could wreck a boundary
5341                 matcher.requireEnd = true;
5342             }
5343             return ((left ^ right) ? (right ? LEFT : RIGHT) : NONE);
5344         }
5345         boolean match(Matcher matcher, int i, CharSequence seq) {
5346             return (check(matcher, i, seq) & type) > 0
5347                 && next.match(matcher, i, seq);
5348         }
5349     }
5350 
5351     /**
5352      * Non spacing marks only count as word characters in bounds calculations
5353      * if they have a base character.
5354      */
5355     private static boolean hasBaseCharacter(Matcher matcher, int i,
5356                                             CharSequence seq)
5357     {
5358         int start = (!matcher.transparentBounds) ?
5359             matcher.from : 0;
5360         for (int x=i; x >= start; x--) {
5361             int ch = Character.codePointAt(seq, x);
5362             if (Character.isLetterOrDigit(ch))
5363                 return true;
5364             if (Character.getType(ch) == Character.NON_SPACING_MARK)
5365                 continue;
5366             return false;
5367         }
5368         return false;
5369     }
5370 
5371     /**
5372      * Attempts to match a slice in the input using the Boyer-Moore string
5373      * matching algorithm. The algorithm is based on the idea that the
5374      * pattern can be shifted farther ahead in the search text if it is
5375      * matched right to left.
5376      * <p>
5377      * The pattern is compared to the input one character at a time, from
5378      * the rightmost character in the pattern to the left. If the characters
5379      * all match the pattern has been found. If a character does not match,
5380      * the pattern is shifted right a distance that is the maximum of two
5381      * functions, the bad character shift and the good suffix shift. This
5382      * shift moves the attempted match position through the input more
5383      * quickly than a naive one position at a time check.
5384      * <p>
5385      * The bad character shift is based on the character from the text that
5386      * did not match. If the character does not appear in the pattern, the
5387      * pattern can be shifted completely beyond the bad character. If the
5388      * character does occur in the pattern, the pattern can be shifted to
5389      * line the pattern up with the next occurrence of that character.
5390      * <p>
5391      * The good suffix shift is based on the idea that some subset on the right
5392      * side of the pattern has matched. When a bad character is found, the
5393      * pattern can be shifted right by the pattern length if the subset does
5394      * not occur again in pattern, or by the amount of distance to the
5395      * next occurrence of the subset in the pattern.
5396      *
5397      * Boyer-Moore search methods adapted from code by Amy Yu.
5398      */
5399     static class BnM extends Node {
5400         int[] buffer;
5401         int[] lastOcc;
5402         int[] optoSft;
5403 
5404         /**
5405          * Pre calculates arrays needed to generate the bad character
5406          * shift and the good suffix shift. Only the last seven bits
5407          * are used to see if chars match; This keeps the tables small
5408          * and covers the heavily used ASCII range, but occasionally
5409          * results in an aliased match for the bad character shift.
5410          */
5411         static Node optimize(Node node) {
5412             if (!(node instanceof Slice)) {
5413                 return node;
5414             }
5415 
5416             int[] src = ((Slice) node).buffer;
5417             int patternLength = src.length;
5418             // The BM algorithm requires a bit of overhead;
5419             // If the pattern is short don't use it, since
5420             // a shift larger than the pattern length cannot
5421             // be used anyway.
5422             if (patternLength < 4) {
5423                 return node;
5424             }
5425             int i, j, k;
5426             int[] lastOcc = new int[128];
5427             int[] optoSft = new int[patternLength];
5428             // Precalculate part of the bad character shift
5429             // It is a table for where in the pattern each
5430             // lower 7-bit value occurs
5431             for (i = 0; i < patternLength; i++) {
5432                 lastOcc[src[i]&0x7F] = i + 1;
5433             }
5434             // Precalculate the good suffix shift
5435             // i is the shift amount being considered
5436 NEXT:       for (i = patternLength; i > 0; i--) {
5437                 // j is the beginning index of suffix being considered
5438                 for (j = patternLength - 1; j >= i; j--) {
5439                     // Testing for good suffix
5440                     if (src[j] == src[j-i]) {
5441                         // src[j..len] is a good suffix
5442                         optoSft[j-1] = i;
5443                     } else {
5444                         // No match. The array has already been
5445                         // filled up with correct values before.
5446                         continue NEXT;
5447                     }
5448                 }
5449                 // This fills up the remaining of optoSft
5450                 // any suffix can not have larger shift amount
5451                 // then its sub-suffix. Why???
5452                 while (j > 0) {
5453                     optoSft[--j] = i;
5454                 }
5455             }
5456             // Set the guard value because of unicode compression
5457             optoSft[patternLength-1] = 1;
5458             if (node instanceof SliceS)
5459                 return new BnMS(src, lastOcc, optoSft, node.next);
5460             return new BnM(src, lastOcc, optoSft, node.next);
5461         }
5462         BnM(int[] src, int[] lastOcc, int[] optoSft, Node next) {
5463             this.buffer = src;
5464             this.lastOcc = lastOcc;
5465             this.optoSft = optoSft;
5466             this.next = next;
5467         }
5468         boolean match(Matcher matcher, int i, CharSequence seq) {
5469             int[] src = buffer;
5470             int patternLength = src.length;
5471             int last = matcher.to - patternLength;
5472 
5473             // Loop over all possible match positions in text
5474 NEXT:       while (i <= last) {
5475                 // Loop over pattern from right to left
5476                 for (int j = patternLength - 1; j >= 0; j--) {
5477                     int ch = seq.charAt(i+j);
5478                     if (ch != src[j]) {
5479                         // Shift search to the right by the maximum of the
5480                         // bad character shift and the good suffix shift
5481                         i += Math.max(j + 1 - lastOcc[ch&0x7F], optoSft[j]);
5482                         continue NEXT;
5483                     }
5484                 }
5485                 // Entire pattern matched starting at i
5486                 matcher.first = i;
5487                 boolean ret = next.match(matcher, i + patternLength, seq);
5488                 if (ret) {
5489                     matcher.first = i;
5490                     matcher.groups[0] = matcher.first;
5491                     matcher.groups[1] = matcher.last;
5492                     return true;
5493                 }
5494                 i++;
5495             }
5496             // BnM is only used as the leading node in the unanchored case,
5497             // and it replaced its Start() which always searches to the end
5498             // if it doesn't find what it's looking for, so hitEnd is true.
5499             matcher.hitEnd = true;
5500             return false;
5501         }
5502         boolean study(TreeInfo info) {
5503             info.minLength += buffer.length;
5504             info.maxValid = false;
5505             return next.study(info);
5506         }
5507     }
5508 
5509     /**
5510      * Supplementary support version of BnM(). Unpaired surrogates are
5511      * also handled by this class.
5512      */
5513     static final class BnMS extends BnM {
5514         int lengthInChars;
5515 
5516         BnMS(int[] src, int[] lastOcc, int[] optoSft, Node next) {
5517             super(src, lastOcc, optoSft, next);
5518             for (int cp : buffer) {
5519                 lengthInChars += Character.charCount(cp);
5520             }
5521         }
5522         boolean match(Matcher matcher, int i, CharSequence seq) {
5523             int[] src = buffer;
5524             int patternLength = src.length;
5525             int last = matcher.to - lengthInChars;
5526 
5527             // Loop over all possible match positions in text
5528 NEXT:       while (i <= last) {
5529                 // Loop over pattern from right to left
5530                 int ch;
5531                 for (int j = countChars(seq, i, patternLength), x = patternLength - 1;
5532                      j > 0; j -= Character.charCount(ch), x--) {
5533                     ch = Character.codePointBefore(seq, i+j);
5534                     if (ch != src[x]) {
5535                         // Shift search to the right by the maximum of the
5536                         // bad character shift and the good suffix shift
5537                         int n = Math.max(x + 1 - lastOcc[ch&0x7F], optoSft[x]);
5538                         i += countChars(seq, i, n);
5539                         continue NEXT;
5540                     }
5541                 }
5542                 // Entire pattern matched starting at i
5543                 matcher.first = i;
5544                 boolean ret = next.match(matcher, i + lengthInChars, seq);
5545                 if (ret) {
5546                     matcher.first = i;
5547                     matcher.groups[0] = matcher.first;
5548                     matcher.groups[1] = matcher.last;
5549                     return true;
5550                 }
5551                 i += countChars(seq, i, 1);
5552             }
5553             matcher.hitEnd = true;
5554             return false;
5555         }
5556     }
5557 
5558 ///////////////////////////////////////////////////////////////////////////////
5559 ///////////////////////////////////////////////////////////////////////////////
5560 
5561     /**
5562      *  This must be the very first initializer.
5563      */
5564     static Node accept = new Node();
5565 
5566     static Node lastAccept = new LastNode();
5567 
5568     private static class CharPropertyNames {
5569 
5570         static CharProperty charPropertyFor(String name) {
5571             CharPropertyFactory m = map.get(name);
5572             return m == null ? null : m.make();
5573         }
5574 
5575         private static abstract class CharPropertyFactory {
5576             abstract CharProperty make();
5577         }
5578 
5579         private static void defCategory(String name,
5580                                         final int typeMask) {
5581             map.put(name, new CharPropertyFactory() {
5582                     CharProperty make() { return new Category(typeMask);}});
5583         }
5584 
5585         private static void defRange(String name,
5586                                      final int lower, final int upper) {
5587             map.put(name, new CharPropertyFactory() {
5588                     CharProperty make() { return rangeFor(lower, upper);}});
5589         }
5590 
5591         private static void defCtype(String name,
5592                                      final int ctype) {
5593             map.put(name, new CharPropertyFactory() {
5594                     CharProperty make() { return new Ctype(ctype);}});
5595         }
5596 
5597         private static abstract class CloneableProperty
5598             extends CharProperty implements Cloneable
5599         {
5600             public CloneableProperty clone() {
5601                 try {
5602                     return (CloneableProperty) super.clone();
5603                 } catch (CloneNotSupportedException e) {
5604                     throw new AssertionError(e);
5605                 }
5606             }
5607         }
5608 
5609         private static void defClone(String name,
5610                                      final CloneableProperty p) {
5611             map.put(name, new CharPropertyFactory() {
5612                     CharProperty make() { return p.clone();}});
5613         }
5614 
5615         private static final HashMap<String, CharPropertyFactory> map
5616             = new HashMap<>();
5617 
5618         static {
5619             // Unicode character property aliases, defined in
5620             // http://www.unicode.org/Public/UNIDATA/PropertyValueAliases.txt
5621             defCategory("Cn", 1<<Character.UNASSIGNED);
5622             defCategory("Lu", 1<<Character.UPPERCASE_LETTER);
5623             defCategory("Ll", 1<<Character.LOWERCASE_LETTER);
5624             defCategory("Lt", 1<<Character.TITLECASE_LETTER);
5625             defCategory("Lm", 1<<Character.MODIFIER_LETTER);
5626             defCategory("Lo", 1<<Character.OTHER_LETTER);
5627             defCategory("Mn", 1<<Character.NON_SPACING_MARK);
5628             defCategory("Me", 1<<Character.ENCLOSING_MARK);
5629             defCategory("Mc", 1<<Character.COMBINING_SPACING_MARK);
5630             defCategory("Nd", 1<<Character.DECIMAL_DIGIT_NUMBER);
5631             defCategory("Nl", 1<<Character.LETTER_NUMBER);
5632             defCategory("No", 1<<Character.OTHER_NUMBER);
5633             defCategory("Zs", 1<<Character.SPACE_SEPARATOR);
5634             defCategory("Zl", 1<<Character.LINE_SEPARATOR);
5635             defCategory("Zp", 1<<Character.PARAGRAPH_SEPARATOR);
5636             defCategory("Cc", 1<<Character.CONTROL);
5637             defCategory("Cf", 1<<Character.FORMAT);
5638             defCategory("Co", 1<<Character.PRIVATE_USE);
5639             defCategory("Cs", 1<<Character.SURROGATE);
5640             defCategory("Pd", 1<<Character.DASH_PUNCTUATION);
5641             defCategory("Ps", 1<<Character.START_PUNCTUATION);
5642             defCategory("Pe", 1<<Character.END_PUNCTUATION);
5643             defCategory("Pc", 1<<Character.CONNECTOR_PUNCTUATION);
5644             defCategory("Po", 1<<Character.OTHER_PUNCTUATION);
5645             defCategory("Sm", 1<<Character.MATH_SYMBOL);
5646             defCategory("Sc", 1<<Character.CURRENCY_SYMBOL);
5647             defCategory("Sk", 1<<Character.MODIFIER_SYMBOL);
5648             defCategory("So", 1<<Character.OTHER_SYMBOL);
5649             defCategory("Pi", 1<<Character.INITIAL_QUOTE_PUNCTUATION);
5650             defCategory("Pf", 1<<Character.FINAL_QUOTE_PUNCTUATION);
5651             defCategory("L", ((1<<Character.UPPERCASE_LETTER) |
5652                               (1<<Character.LOWERCASE_LETTER) |
5653                               (1<<Character.TITLECASE_LETTER) |
5654                               (1<<Character.MODIFIER_LETTER)  |
5655                               (1<<Character.OTHER_LETTER)));
5656             defCategory("M", ((1<<Character.NON_SPACING_MARK) |
5657                               (1<<Character.ENCLOSING_MARK)   |
5658                               (1<<Character.COMBINING_SPACING_MARK)));
5659             defCategory("N", ((1<<Character.DECIMAL_DIGIT_NUMBER) |
5660                               (1<<Character.LETTER_NUMBER)        |
5661                               (1<<Character.OTHER_NUMBER)));
5662             defCategory("Z", ((1<<Character.SPACE_SEPARATOR) |
5663                               (1<<Character.LINE_SEPARATOR)  |
5664                               (1<<Character.PARAGRAPH_SEPARATOR)));
5665             defCategory("C", ((1<<Character.CONTROL)     |
5666                               (1<<Character.FORMAT)      |
5667                               (1<<Character.PRIVATE_USE) |
5668                               (1<<Character.SURROGATE))); // Other
5669             defCategory("P", ((1<<Character.DASH_PUNCTUATION)      |
5670                               (1<<Character.START_PUNCTUATION)     |
5671                               (1<<Character.END_PUNCTUATION)       |
5672                               (1<<Character.CONNECTOR_PUNCTUATION) |
5673                               (1<<Character.OTHER_PUNCTUATION)     |
5674                               (1<<Character.INITIAL_QUOTE_PUNCTUATION) |
5675                               (1<<Character.FINAL_QUOTE_PUNCTUATION)));
5676             defCategory("S", ((1<<Character.MATH_SYMBOL)     |
5677                               (1<<Character.CURRENCY_SYMBOL) |
5678                               (1<<Character.MODIFIER_SYMBOL) |
5679                               (1<<Character.OTHER_SYMBOL)));
5680             defCategory("LC", ((1<<Character.UPPERCASE_LETTER) |
5681                                (1<<Character.LOWERCASE_LETTER) |
5682                                (1<<Character.TITLECASE_LETTER)));
5683             defCategory("LD", ((1<<Character.UPPERCASE_LETTER) |
5684                                (1<<Character.LOWERCASE_LETTER) |
5685                                (1<<Character.TITLECASE_LETTER) |
5686                                (1<<Character.MODIFIER_LETTER)  |
5687                                (1<<Character.OTHER_LETTER)     |
5688                                (1<<Character.DECIMAL_DIGIT_NUMBER)));
5689             defRange("L1", 0x00, 0xFF); // Latin-1
5690             map.put("all", new CharPropertyFactory() {
5691                     CharProperty make() { return new All(); }});
5692 
5693             // Posix regular expression character classes, defined in
5694             // http://www.unix.org/onlinepubs/009695399/basedefs/xbd_chap09.html
5695             defRange("ASCII", 0x00, 0x7F);   // ASCII
5696             defCtype("Alnum", ASCII.ALNUM);  // Alphanumeric characters
5697             defCtype("Alpha", ASCII.ALPHA);  // Alphabetic characters
5698             defCtype("Blank", ASCII.BLANK);  // Space and tab characters
5699             defCtype("Cntrl", ASCII.CNTRL);  // Control characters
5700             defRange("Digit", '0', '9');     // Numeric characters
5701             defCtype("Graph", ASCII.GRAPH);  // printable and visible
5702             defRange("Lower", 'a', 'z');     // Lower-case alphabetic
5703             defRange("Print", 0x20, 0x7E);   // Printable characters
5704             defCtype("Punct", ASCII.PUNCT);  // Punctuation characters
5705             defCtype("Space", ASCII.SPACE);  // Space characters
5706             defRange("Upper", 'A', 'Z');     // Upper-case alphabetic
5707             defCtype("XDigit",ASCII.XDIGIT); // hexadecimal digits
5708 
5709             // Java character properties, defined by methods in Character.java
5710             defClone("javaLowerCase", new CloneableProperty() {
5711                 boolean isSatisfiedBy(int ch) {
5712                     return Character.isLowerCase(ch);}});
5713             defClone("javaUpperCase", new CloneableProperty() {
5714                 boolean isSatisfiedBy(int ch) {
5715                     return Character.isUpperCase(ch);}});
5716             defClone("javaAlphabetic", new CloneableProperty() {
5717                 boolean isSatisfiedBy(int ch) {
5718                     return Character.isAlphabetic(ch);}});
5719             defClone("javaIdeographic", new CloneableProperty() {
5720                 boolean isSatisfiedBy(int ch) {
5721                     return Character.isIdeographic(ch);}});
5722             defClone("javaTitleCase", new CloneableProperty() {
5723                 boolean isSatisfiedBy(int ch) {
5724                     return Character.isTitleCase(ch);}});
5725             defClone("javaDigit", new CloneableProperty() {
5726                 boolean isSatisfiedBy(int ch) {
5727                     return Character.isDigit(ch);}});
5728             defClone("javaDefined", new CloneableProperty() {
5729                 boolean isSatisfiedBy(int ch) {
5730                     return Character.isDefined(ch);}});
5731             defClone("javaLetter", new CloneableProperty() {
5732                 boolean isSatisfiedBy(int ch) {
5733                     return Character.isLetter(ch);}});
5734             defClone("javaLetterOrDigit", new CloneableProperty() {
5735                 boolean isSatisfiedBy(int ch) {
5736                     return Character.isLetterOrDigit(ch);}});
5737             defClone("javaJavaIdentifierStart", new CloneableProperty() {
5738                 boolean isSatisfiedBy(int ch) {
5739                     return Character.isJavaIdentifierStart(ch);}});
5740             defClone("javaJavaIdentifierPart", new CloneableProperty() {
5741                 boolean isSatisfiedBy(int ch) {
5742                     return Character.isJavaIdentifierPart(ch);}});
5743             defClone("javaUnicodeIdentifierStart", new CloneableProperty() {
5744                 boolean isSatisfiedBy(int ch) {
5745                     return Character.isUnicodeIdentifierStart(ch);}});
5746             defClone("javaUnicodeIdentifierPart", new CloneableProperty() {
5747                 boolean isSatisfiedBy(int ch) {
5748                     return Character.isUnicodeIdentifierPart(ch);}});
5749             defClone("javaIdentifierIgnorable", new CloneableProperty() {
5750                 boolean isSatisfiedBy(int ch) {
5751                     return Character.isIdentifierIgnorable(ch);}});
5752             defClone("javaSpaceChar", new CloneableProperty() {
5753                 boolean isSatisfiedBy(int ch) {
5754                     return Character.isSpaceChar(ch);}});
5755             defClone("javaWhitespace", new CloneableProperty() {
5756                 boolean isSatisfiedBy(int ch) {
5757                     return Character.isWhitespace(ch);}});
5758             defClone("javaISOControl", new CloneableProperty() {
5759                 boolean isSatisfiedBy(int ch) {
5760                     return Character.isISOControl(ch);}});
5761             defClone("javaMirrored", new CloneableProperty() {
5762                 boolean isSatisfiedBy(int ch) {
5763                     return Character.isMirrored(ch);}});
5764         }
5765     }
5766 
5767     /**
5768      * Creates a predicate which can be used to match a string.
5769      *
5770      * @return  The predicate which can be used for matching on a string
5771      * @since   1.8
5772      */
5773     public Predicate<String> asPredicate() {
5774         return s -> matcher(s).find();
5775     }
5776 
5777     /**
5778      * Creates a stream from the given input sequence around matches of this
5779      * pattern.
5780      *
5781      * <p> The stream returned by this method contains each substring of the
5782      * input sequence that is terminated by another subsequence that matches
5783      * this pattern or is terminated by the end of the input sequence.  The
5784      * substrings in the stream are in the order in which they occur in the
5785      * input. Trailing empty strings will be discarded and not encountered in
5786      * the stream.
5787      *
5788      * <p> If this pattern does not match any subsequence of the input then
5789      * the resulting stream has just one element, namely the input sequence in
5790      * string form.
5791      *
5792      * <p> When there is a positive-width match at the beginning of the input
5793      * sequence then an empty leading substring is included at the beginning
5794      * of the stream. A zero-width match at the beginning however never produces
5795      * such empty leading substring.
5796      *
5797      * <p> If the input sequence is mutable, it must remain constant during the
5798      * execution of the terminal stream operation.  Otherwise, the result of the
5799      * terminal stream operation is undefined.
5800      *
5801      * @param   input
5802      *          The character sequence to be split
5803      *
5804      * @return  The stream of strings computed by splitting the input
5805      *          around matches of this pattern
5806      * @see     #split(CharSequence)
5807      * @since   1.8
5808      */
5809     public Stream<String> splitAsStream(final CharSequence input) {
5810         class MatcherIterator implements Iterator<String> {
5811             private final Matcher matcher;
5812             // The start position of the next sub-sequence of input
5813             // when current == input.length there are no more elements
5814             private int current;
5815             // null if the next element, if any, needs to obtained
5816             private String nextElement;
5817             // > 0 if there are N next empty elements
5818             private int emptyElementCount;
5819 
5820             MatcherIterator() {
5821                 this.matcher = matcher(input);
5822                 // If the input is an empty string then the result can only be a
5823                 // stream of the input.  Induce that by setting the empty
5824                 // element count to 1
5825                 this.emptyElementCount = input.length() == 0 ? 1 : 0;
5826             }
5827 
5828             public String next() {
5829                 if (!hasNext())
5830                     throw new NoSuchElementException();
5831 
5832                 if (emptyElementCount == 0) {
5833                     String n = nextElement;
5834                     nextElement = null;
5835                     return n;
5836                 } else {
5837                     emptyElementCount--;
5838                     return "";
5839                 }
5840             }
5841 
5842             public boolean hasNext() {
5843                 if (nextElement != null || emptyElementCount > 0)
5844                     return true;
5845 
5846                 if (current == input.length())
5847                     return false;
5848 
5849                 // Consume the next matching element
5850                 // Count sequence of matching empty elements
5851                 while (matcher.find()) {
5852                     nextElement = input.subSequence(current, matcher.start()).toString();
5853                     current = matcher.end();
5854                     if (!nextElement.isEmpty()) {
5855                         return true;
5856                     } else if (current > 0) { // no empty leading substring for zero-width
5857                                               // match at the beginning of the input
5858                         emptyElementCount++;
5859                     }
5860                 }
5861 
5862                 // Consume last matching element
5863                 nextElement = input.subSequence(current, input.length()).toString();
5864                 current = input.length();
5865                 if (!nextElement.isEmpty()) {
5866                     return true;
5867                 } else {
5868                     // Ignore a terminal sequence of matching empty elements
5869                     emptyElementCount = 0;
5870                     nextElement = null;
5871                     return false;
5872                 }
5873             }
5874         }
5875         return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
5876                 new MatcherIterator(), Spliterator.ORDERED | Spliterator.NONNULL), false);
5877     }
5878 }
--- EOF ---