64 * <p> A {@link #matches matches} method is defined by this class as a
65 * convenience for when a regular expression is used just once. This method
66 * compiles an expression and matches an input sequence against it in a single
67 * invocation. The statement
68 *
69 * <blockquote><pre>
70 * boolean b = Pattern.matches("a*b", "aaaaab");</pre></blockquote>
71 *
72 * is equivalent to the three statements above, though for repeated matches it
73 * is less efficient since it does not allow the compiled pattern to be reused.
74 *
75 * <p> Instances of this class are immutable and are safe for use by multiple
76 * concurrent threads. Instances of the {@link Matcher} class are not safe for
77 * such use.
78 *
79 *
80 * <h3><a id="sum">Summary of regular-expression constructs</a></h3>
81 *
82 * <table class="borderless">
83 * <caption style="display:none">Regular expression constructs, and what they match</caption>
84 * <thead>
85 * <tr style="text-align:left">
86 * <th style="text-align:left" id="construct">Construct</th>
87 * <th style="text-align:left" id="matches">Matches</th>
88 * </tr>
89 * </thead>
90 * <tbody>
91 *
92 * <tr><th> </th></tr>
93 * <tr style="text-align:left"><th colspan="2" id="characters">Characters</th></tr>
94 *
95 * <tr><td style="vertical-align:top" headers="construct characters"><i>x</i></td>
96 * <td headers="matches">The character <i>x</i></td></tr>
97 * <tr><td style="vertical-align:top" headers="construct characters">{@code \\}</td>
98 * <td headers="matches">The backslash character</td></tr>
99 * <tr><td style="vertical-align:top" headers="construct characters">{@code \0}<i>n</i></td>
100 * <td headers="matches">The character with octal value {@code 0}<i>n</i>
101 * (0 {@code <=} <i>n</i> {@code <=} 7)</td></tr>
102 * <tr><td style="vertical-align:top" headers="construct characters">{@code \0}<i>nn</i></td>
103 * <td headers="matches">The character with octal value {@code 0}<i>nn</i>
104 * (0 {@code <=} <i>n</i> {@code <=} 7)</td></tr>
105 * <tr><td style="vertical-align:top" headers="construct characters">{@code \0}<i>mnn</i></td>
106 * <td headers="matches">The character with octal value {@code 0}<i>mnn</i>
107 * (0 {@code <=} <i>m</i> {@code <=} 3,
108 * 0 {@code <=} <i>n</i> {@code <=} 7)</td></tr>
109 * <tr><td style="vertical-align:top" headers="construct characters">{@code \x}<i>hh</i></td>
110 * <td headers="matches">The character with hexadecimal value {@code 0x}<i>hh</i></td></tr>
111 * <tr><td style="vertical-align:top" headers="construct characters"><code>\u</code><i>hhhh</i></td>
112 * <td headers="matches">The character with hexadecimal value {@code 0x}<i>hhhh</i></td></tr>
113 * <tr><td style="vertical-align:top" headers="construct characters"><code>\x</code><i>{h...h}</i></td>
114 * <td headers="matches">The character with hexadecimal value {@code 0x}<i>h...h</i>
115 * ({@link java.lang.Character#MIN_CODE_POINT Character.MIN_CODE_POINT}
116 * <= {@code 0x}<i>h...h</i> <=
117 * {@link java.lang.Character#MAX_CODE_POINT Character.MAX_CODE_POINT})</td></tr>
118 * <tr><td style="vertical-align:top" headers="construct characters"><code>\N{</code><i>name</i><code>}</code></td>
119 * <td headers="matches">The character with Unicode character name <i>'name'</i></td></tr>
120 * <tr><td style="vertical-align:top" headers="matches">{@code \t}</td>
121 * <td headers="matches">The tab character (<code>'\u0009'</code>)</td></tr>
122 * <tr><td style="vertical-align:top" headers="construct characters">{@code \n}</td>
123 * <td headers="matches">The newline (line feed) character (<code>'\u000A'</code>)</td></tr>
124 * <tr><td style="vertical-align:top" headers="construct characters">{@code \r}</td>
125 * <td headers="matches">The carriage-return character (<code>'\u000D'</code>)</td></tr>
126 * <tr><td style="vertical-align:top" headers="construct characters">{@code \f}</td>
127 * <td headers="matches">The form-feed character (<code>'\u000C'</code>)</td></tr>
128 * <tr><td style="vertical-align:top" headers="construct characters">{@code \a}</td>
129 * <td headers="matches">The alert (bell) character (<code>'\u0007'</code>)</td></tr>
130 * <tr><td style="vertical-align:top" headers="construct characters">{@code \e}</td>
131 * <td headers="matches">The escape character (<code>'\u001B'</code>)</td></tr>
132 * <tr><td style="vertical-align:top" headers="construct characters">{@code \c}<i>x</i></td>
133 * <td headers="matches">The control character corresponding to <i>x</i></td></tr>
134 *
135 * <tr><th> </th></tr>
136 * <tr style="text-align:left"><th colspan="2" id="classes">Character classes</th></tr>
137 *
138 * <tr><td style="vertical-align:top" headers="construct classes">{@code [abc]}</td>
139 * <td headers="matches">{@code a}, {@code b}, or {@code c} (simple class)</td></tr>
140 * <tr><td style="vertical-align:top" headers="construct classes">{@code [^abc]}</td>
141 * <td headers="matches">Any character except {@code a}, {@code b}, or {@code c} (negation)</td></tr>
142 * <tr><td style="vertical-align:top" headers="construct classes">{@code [a-zA-Z]}</td>
143 * <td headers="matches">{@code a} through {@code z}
144 * or {@code A} through {@code Z}, inclusive (range)</td></tr>
145 * <tr><td style="vertical-align:top" headers="construct classes">{@code [a-d[m-p]]}</td>
146 * <td headers="matches">{@code a} through {@code d},
147 * or {@code m} through {@code p}: {@code [a-dm-p]} (union)</td></tr>
148 * <tr><td style="vertical-align:top" headers="construct classes">{@code [a-z&&[def]]}</td>
149 * <td headers="matches">{@code d}, {@code e}, or {@code f} (intersection)</tr>
150 * <tr><td style="vertical-align:top" headers="construct classes">{@code [a-z&&[^bc]]}</td>
151 * <td headers="matches">{@code a} through {@code z},
152 * except for {@code b} and {@code c}: {@code [ad-z]} (subtraction)</td></tr>
153 * <tr><td style="vertical-align:top" headers="construct classes">{@code [a-z&&[^m-p]]}</td>
154 * <td headers="matches">{@code a} through {@code z},
155 * and not {@code m} through {@code p}: {@code [a-lq-z]}(subtraction)</td></tr>
156 * <tr><th> </th></tr>
157 *
158 * <tr style="text-align:left"><th colspan="2" id="predef">Predefined character classes</th></tr>
159 *
160 * <tr><td style="vertical-align:top" headers="construct predef">{@code .}</td>
161 * <td headers="matches">Any character (may or may not match <a href="#lt">line terminators</a>)</td></tr>
162 * <tr><td style="vertical-align:top" headers="construct predef">{@code \d}</td>
163 * <td headers="matches">A digit: {@code [0-9]}</td></tr>
164 * <tr><td style="vertical-align:top" headers="construct predef">{@code \D}</td>
165 * <td headers="matches">A non-digit: {@code [^0-9]}</td></tr>
166 * <tr><td style="vertical-align:top" headers="construct predef">{@code \h}</td>
167 * <td headers="matches">A horizontal whitespace character:
168 * <code>[ \t\xA0\u1680\u180e\u2000-\u200a\u202f\u205f\u3000]</code></td></tr>
169 * <tr><td style="vertical-align:top" headers="construct predef">{@code \H}</td>
170 * <td headers="matches">A non-horizontal whitespace character: {@code [^\h]}</td></tr>
171 * <tr><td style="vertical-align:top" headers="construct predef">{@code \s}</td>
172 * <td headers="matches">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
173 * <tr><td style="vertical-align:top" headers="construct predef">{@code \S}</td>
174 * <td headers="matches">A non-whitespace character: {@code [^\s]}</td></tr>
175 * <tr><td style="vertical-align:top" headers="construct predef">{@code \v}</td>
176 * <td headers="matches">A vertical whitespace character: <code>[\n\x0B\f\r\x85\u2028\u2029]</code>
177 * </td></tr>
178 * <tr><td style="vertical-align:top" headers="construct predef">{@code \V}</td>
179 * <td headers="matches">A non-vertical whitespace character: {@code [^\v]}</td></tr>
180 * <tr><td style="vertical-align:top" headers="construct predef">{@code \w}</td>
181 * <td headers="matches">A word character: {@code [a-zA-Z_0-9]}</td></tr>
182 * <tr><td style="vertical-align:top" headers="construct predef">{@code \W}</td>
183 * <td headers="matches">A non-word character: {@code [^\w]}</td></tr>
184 * <tr><th> </th></tr>
185 * <tr style="text-align:left"><th colspan="2" id="posix"><b>POSIX character classes (US-ASCII only)</b></th></tr>
186 *
187 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Lower}}</td>
188 * <td headers="matches">A lower-case alphabetic character: {@code [a-z]}</td></tr>
189 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Upper}}</td>
190 * <td headers="matches">An upper-case alphabetic character:{@code [A-Z]}</td></tr>
191 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{ASCII}}</td>
192 * <td headers="matches">All ASCII:{@code [\x00-\x7F]}</td></tr>
193 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Alpha}}</td>
194 * <td headers="matches">An alphabetic character:{@code [\p{Lower}\p{Upper}]}</td></tr>
195 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Digit}}</td>
196 * <td headers="matches">A decimal digit: {@code [0-9]}</td></tr>
197 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Alnum}}</td>
198 * <td headers="matches">An alphanumeric character:{@code [\p{Alpha}\p{Digit}]}</td></tr>
199 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Punct}}</td>
200 * <td headers="matches">Punctuation: One of {@code !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~}</td></tr>
201 * <!-- {@code [\!"#\$%&'\(\)\*\+,\-\./:;\<=\>\?@\[\\\]\^_`\{\|\}~]}
202 * {@code [\X21-\X2F\X31-\X40\X5B-\X60\X7B-\X7E]} -->
203 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Graph}}</td>
204 * <td headers="matches">A visible character: {@code [\p{Alnum}\p{Punct}]}</td></tr>
205 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Print}}</td>
206 * <td headers="matches">A printable character: {@code [\p{Graph}\x20]}</td></tr>
207 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Blank}}</td>
208 * <td headers="matches">A space or a tab: {@code [ \t]}</td></tr>
209 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Cntrl}}</td>
210 * <td headers="matches">A control character: {@code [\x00-\x1F\x7F]}</td></tr>
211 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{XDigit}}</td>
212 * <td headers="matches">A hexadecimal digit: {@code [0-9a-fA-F]}</td></tr>
213 * <tr><td style="vertical-align:top" headers="construct posix">{@code \p{Space}}</td>
214 * <td headers="matches">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
215 *
216 * <tr><th> </th></tr>
217 * <tr style="text-align:left"><th colspan="2">java.lang.Character classes (simple <a href="#jcc">java character type</a>)</th></tr>
218 *
219 * <tr><td style="vertical-align:top">{@code \p{javaLowerCase}}</td>
220 * <td>Equivalent to java.lang.Character.isLowerCase()</td></tr>
221 * <tr><td style="vertical-align:top">{@code \p{javaUpperCase}}</td>
222 * <td>Equivalent to java.lang.Character.isUpperCase()</td></tr>
223 * <tr><td style="vertical-align:top">{@code \p{javaWhitespace}}</td>
224 * <td>Equivalent to java.lang.Character.isWhitespace()</td></tr>
225 * <tr><td style="vertical-align:top">{@code \p{javaMirrored}}</td>
226 * <td>Equivalent to java.lang.Character.isMirrored()</td></tr>
227 *
228 * <tr><th> </th></tr>
229 * <tr style="text-align:left"><th colspan="2" id="unicode">Classes for Unicode scripts, blocks, categories and binary properties</th></tr>
230 * <tr><td style="vertical-align:top" headers="construct unicode">{@code \p{IsLatin}}</td>
231 * <td headers="matches">A Latin script character (<a href="#usc">script</a>)</td></tr>
232 * <tr><td style="vertical-align:top" headers="construct unicode">{@code \p{InGreek}}</td>
233 * <td headers="matches">A character in the Greek block (<a href="#ubc">block</a>)</td></tr>
234 * <tr><td style="vertical-align:top" headers="construct unicode">{@code \p{Lu}}</td>
235 * <td headers="matches">An uppercase letter (<a href="#ucc">category</a>)</td></tr>
236 * <tr><td style="vertical-align:top" headers="construct unicode">{@code \p{IsAlphabetic}}</td>
237 * <td headers="matches">An alphabetic character (<a href="#ubpc">binary property</a>)</td></tr>
238 * <tr><td style="vertical-align:top" headers="construct unicode">{@code \p{Sc}}</td>
239 * <td headers="matches">A currency symbol</td></tr>
240 * <tr><td style="vertical-align:top" headers="construct unicode">{@code \P{InGreek}}</td>
241 * <td headers="matches">Any character except one in the Greek block (negation)</td></tr>
242 * <tr><td style="vertical-align:top" headers="construct unicode">{@code [\p{L}&&[^\p{Lu}]]}</td>
243 * <td headers="matches">Any letter except an uppercase letter (subtraction)</td></tr>
244 *
245 * <tr><th> </th></tr>
246 * <tr style="text-align:left"><th colspan="2" id="bounds">Boundary matchers</th></tr>
247 *
248 * <tr><td style="vertical-align:top" headers="construct bounds">{@code ^}</td>
249 * <td headers="matches">The beginning of a line</td></tr>
250 * <tr><td style="vertical-align:top" headers="construct bounds">{@code $}</td>
251 * <td headers="matches">The end of a line</td></tr>
252 * <tr><td style="vertical-align:top" headers="construct bounds">{@code \b}</td>
253 * <td headers="matches">A word boundary</td></tr>
254 * <tr><td style="vertical-align:top" headers="construct bounds">{@code \b{g}}</td>
255 * <td headers="matches">A Unicode extended grapheme cluster boundary</td></tr>
256 * <tr><td style="vertical-align:top" headers="construct bounds">{@code \B}</td>
257 * <td headers="matches">A non-word boundary</td></tr>
258 * <tr><td style="vertical-align:top" headers="construct bounds">{@code \A}</td>
259 * <td headers="matches">The beginning of the input</td></tr>
260 * <tr><td style="vertical-align:top" headers="construct bounds">{@code \G}</td>
261 * <td headers="matches">The end of the previous match</td></tr>
262 * <tr><td style="vertical-align:top" headers="construct bounds">{@code \Z}</td>
263 * <td headers="matches">The end of the input but for the final
264 * <a href="#lt">terminator</a>, if any</td></tr>
265 * <tr><td style="vertical-align:top" headers="construct bounds">{@code \z}</td>
266 * <td headers="matches">The end of the input</td></tr>
267 *
268 * <tr><th> </th></tr>
269 * <tr style="text-align:left"><th colspan="2" id="lineending">Linebreak matcher</th></tr>
270 * <tr><td style="vertical-align:top" headers="construct lineending">{@code \R}</td>
271 * <td headers="matches">Any Unicode linebreak sequence, is equivalent to
272 * <code>\u000D\u000A|[\u000A\u000B\u000C\u000D\u0085\u2028\u2029]
273 * </code></td></tr>
274 *
275 * <tr><th> </th></tr>
276 * <tr style="text-align:left"><th colspan="2" id="grapheme">Unicode Extended Grapheme matcher</th></tr>
277 * <tr><td style="vertical-align:top" headers="construct grapheme">{@code \X}</td>
278 * <td headers="matches">Any Unicode extended grapheme cluster</td></tr>
279 *
280 * <tr><th> </th></tr>
281 * <tr style="text-align:left"><th colspan="2" id="greedy">Greedy quantifiers</th></tr>
282 *
283 * <tr><td style="vertical-align:top" headers="construct greedy"><i>X</i>{@code ?}</td>
284 * <td headers="matches"><i>X</i>, once or not at all</td></tr>
285 * <tr><td style="vertical-align:top" headers="construct greedy"><i>X</i>{@code *}</td>
286 * <td headers="matches"><i>X</i>, zero or more times</td></tr>
287 * <tr><td style="vertical-align:top" headers="construct greedy"><i>X</i>{@code +}</td>
288 * <td headers="matches"><i>X</i>, one or more times</td></tr>
289 * <tr><td style="vertical-align:top" headers="construct greedy"><i>X</i><code>{</code><i>n</i><code>}</code></td>
290 * <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
291 * <tr><td style="vertical-align:top" headers="construct greedy"><i>X</i><code>{</code><i>n</i>{@code ,}}</td>
292 * <td headers="matches"><i>X</i>, at least <i>n</i> times</td></tr>
293 * <tr><td style="vertical-align:top" headers="construct greedy"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}</code></td>
294 * <td headers="matches"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
295 *
296 * <tr><th> </th></tr>
297 * <tr style="text-align:left"><th colspan="2" id="reluc">Reluctant quantifiers</th></tr>
298 *
299 * <tr><td style="vertical-align:top" headers="construct reluc"><i>X</i>{@code ??}</td>
300 * <td headers="matches"><i>X</i>, once or not at all</td></tr>
301 * <tr><td style="vertical-align:top" headers="construct reluc"><i>X</i>{@code *?}</td>
302 * <td headers="matches"><i>X</i>, zero or more times</td></tr>
303 * <tr><td style="vertical-align:top" headers="construct reluc"><i>X</i>{@code +?}</td>
304 * <td headers="matches"><i>X</i>, one or more times</td></tr>
305 * <tr><td style="vertical-align:top" headers="construct reluc"><i>X</i><code>{</code><i>n</i><code>}?</code></td>
306 * <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
307 * <tr><td style="vertical-align:top" headers="construct reluc"><i>X</i><code>{</code><i>n</i><code>,}?</code></td>
308 * <td headers="matches"><i>X</i>, at least <i>n</i> times</td></tr>
309 * <tr><td style="vertical-align:top" headers="construct reluc"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}?</code></td>
310 * <td headers="matches"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
311 *
312 * <tr><th> </th></tr>
313 * <tr style="text-align:left"><th colspan="2" id="poss">Possessive quantifiers</th></tr>
314 *
315 * <tr><td style="vertical-align:top" headers="construct poss"><i>X</i>{@code ?+}</td>
316 * <td headers="matches"><i>X</i>, once or not at all</td></tr>
317 * <tr><td style="vertical-align:top" headers="construct poss"><i>X</i>{@code *+}</td>
318 * <td headers="matches"><i>X</i>, zero or more times</td></tr>
319 * <tr><td style="vertical-align:top" headers="construct poss"><i>X</i>{@code ++}</td>
320 * <td headers="matches"><i>X</i>, one or more times</td></tr>
321 * <tr><td style="vertical-align:top" headers="construct poss"><i>X</i><code>{</code><i>n</i><code>}+</code></td>
322 * <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
323 * <tr><td style="vertical-align:top" headers="construct poss"><i>X</i><code>{</code><i>n</i><code>,}+</code></td>
324 * <td headers="matches"><i>X</i>, at least <i>n</i> times</td></tr>
325 * <tr><td style="vertical-align:top" headers="construct poss"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}+</code></td>
326 * <td headers="matches"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
327 *
328 * <tr><th> </th></tr>
329 * <tr style="text-align:left"><th colspan="2" id="logical">Logical operators</th></tr>
330 *
331 * <tr><td style="vertical-align:top" headers="construct logical"><i>XY</i></td>
332 * <td headers="matches"><i>X</i> followed by <i>Y</i></td></tr>
333 * <tr><td style="vertical-align:top" headers="construct logical"><i>X</i>{@code |}<i>Y</i></td>
334 * <td headers="matches">Either <i>X</i> or <i>Y</i></td></tr>
335 * <tr><td style="vertical-align:top" headers="construct logical">{@code (}<i>X</i>{@code )}</td>
336 * <td headers="matches">X, as a <a href="#cg">capturing group</a></td></tr>
337 *
338 * <tr><th> </th></tr>
339 * <tr style="text-align:left"><th colspan="2" id="backref">Back references</th></tr>
340 *
341 * <tr><td style="vertical-align:bottom" headers="construct backref">{@code \}<i>n</i></td>
342 * <td style="vertical-align:bottom" headers="matches">Whatever the <i>n</i><sup>th</sup>
343 * <a href="#cg">capturing group</a> matched</td></tr>
344 *
345 * <tr><td style="vertical-align:bottom" headers="construct backref">{@code \}<i>k</i><<i>name</i>></td>
346 * <td style="vertical-align:bottom" headers="matches">Whatever the
347 * <a href="#groupname">named-capturing group</a> "name" matched</td></tr>
348 *
349 * <tr><th> </th></tr>
350 * <tr style="text-align:left"><th colspan="2" id="quot">Quotation</th></tr>
351 *
352 * <tr><td style="vertical-align:top" headers="construct quot">{@code \}</td>
353 * <td headers="matches">Nothing, but quotes the following character</td></tr>
354 * <tr><td style="vertical-align:top" headers="construct quot">{@code \Q}</td>
355 * <td headers="matches">Nothing, but quotes all characters until {@code \E}</td></tr>
356 * <tr><td style="vertical-align:top" headers="construct quot">{@code \E}</td>
357 * <td headers="matches">Nothing, but ends quoting started by {@code \Q}</td></tr>
358 * <!-- Metachars: !$()*+.<>?[\]^{|} -->
359 *
360 * <tr><th> </th></tr>
361 * <tr style="text-align:left"><th colspan="2" id="special">Special constructs (named-capturing and non-capturing)</th></tr>
362 *
363 * <tr><td style="vertical-align:top" headers="construct special"><code>(?<<a href="#groupname">name</a>></code><i>X</i>{@code )}</td>
364 * <td headers="matches"><i>X</i>, as a named-capturing group</td></tr>
365 * <tr><td style="vertical-align:top" headers="construct special">{@code (?:}<i>X</i>{@code )}</td>
366 * <td headers="matches"><i>X</i>, as a non-capturing group</td></tr>
367 * <tr><td style="vertical-align:top" headers="construct special"><code>(?idmsuxU-idmsuxU) </code></td>
368 * <td headers="matches">Nothing, but turns match flags <a href="#CASE_INSENSITIVE">i</a>
369 * <a href="#UNIX_LINES">d</a> <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a>
370 * <a href="#UNICODE_CASE">u</a> <a href="#COMMENTS">x</a> <a href="#UNICODE_CHARACTER_CLASS">U</a>
371 * on - off</td></tr>
372 * <tr><td style="vertical-align:top" headers="construct special"><code>(?idmsux-idmsux:</code><i>X</i>{@code )} </td>
373 * <td headers="matches"><i>X</i>, as a <a href="#cg">non-capturing group</a> with the
374 * given flags <a href="#CASE_INSENSITIVE">i</a> <a href="#UNIX_LINES">d</a>
375 * <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a> <a href="#UNICODE_CASE">u</a >
376 * <a href="#COMMENTS">x</a> on - off</td></tr>
377 * <tr><td style="vertical-align:top" headers="construct special">{@code (?=}<i>X</i>{@code )}</td>
378 * <td headers="matches"><i>X</i>, via zero-width positive lookahead</td></tr>
379 * <tr><td style="vertical-align:top" headers="construct special">{@code (?!}<i>X</i>{@code )}</td>
380 * <td headers="matches"><i>X</i>, via zero-width negative lookahead</td></tr>
381 * <tr><td style="vertical-align:top" headers="construct special">{@code (?<=}<i>X</i>{@code )}</td>
382 * <td headers="matches"><i>X</i>, via zero-width positive lookbehind</td></tr>
383 * <tr><td style="vertical-align:top" headers="construct special">{@code (?<!}<i>X</i>{@code )}</td>
384 * <td headers="matches"><i>X</i>, via zero-width negative lookbehind</td></tr>
385 * <tr><td style="vertical-align:top" headers="construct special">{@code (?>}<i>X</i>{@code )}</td>
386 * <td headers="matches"><i>X</i>, as an independent, non-capturing group</td></tr>
387 *
388 * </tbody>
389 * </table>
390 *
391 * <hr>
392 *
393 *
394 * <h3><a id="bs">Backslashes, escapes, and quoting</a></h3>
395 *
396 * <p> The backslash character ({@code '\'}) serves to introduce escaped
397 * constructs, as defined in the table above, as well as to quote characters
398 * that otherwise would be interpreted as unescaped constructs. Thus the
399 * expression {@code \\} matches a single backslash and <code>\{</code> matches a
400 * left brace.
401 *
402 * <p> It is an error to use a backslash prior to any alphabetic character that
403 * does not denote an escaped construct; these are reserved for future
404 * extensions to the regular-expression language. A backslash may be used
405 * prior to a non-alphabetic character regardless of whether that character is
406 * part of an unescaped construct.
415 * <code>"\b"</code>, for example, matches a single backspace character when
416 * interpreted as a regular expression, while {@code "\\b"} matches a
417 * word boundary. The string literal {@code "\(hello\)"} is illegal
418 * and leads to a compile-time error; in order to match the string
419 * {@code (hello)} the string literal {@code "\\(hello\\)"}
420 * must be used.
421 *
422 * <h3><a id="cc">Character Classes</a></h3>
423 *
424 * <p> Character classes may appear within other character classes, and
425 * may be composed by the union operator (implicit) and the intersection
426 * operator ({@code &&}).
427 * The union operator denotes a class that contains every character that is
428 * in at least one of its operand classes. The intersection operator
429 * denotes a class that contains every character that is in both of its
430 * operand classes.
431 *
432 * <p> The precedence of character-class operators is as follows, from
433 * highest to lowest:
434 *
435 * <blockquote><table>
436 * <caption style="display:none">Precedence of character class operators.</caption>
437 * <tbody>
438 * <tr><th>1 </th>
439 * <td>Literal escape </td>
440 * <td>{@code \x}</td></tr>
441 * <tr><th>2 </th>
442 * <td>Grouping</td>
443 * <td>{@code [...]}</td></tr>
444 * <tr><th>3 </th>
445 * <td>Range</td>
446 * <td>{@code a-z}</td></tr>
447 * <tr><th>4 </th>
448 * <td>Union</td>
449 * <td>{@code [a-e][i-u]}</td></tr>
450 * <tr><th>5 </th>
451 * <td>Intersection</td>
452 * <td>{@code [a-z&&[aeiou]]}</td></tr>
453 * </tbody>
454 * </table></blockquote>
455 *
456 * <p> Note that a different set of metacharacters are in effect inside
457 * a character class than outside a character class. For instance, the
458 * regular expression {@code .} loses its special meaning inside a
459 * character class, while the expression {@code -} becomes a range
460 * forming metacharacter.
461 *
462 * <h3><a id="lt">Line terminators</a></h3>
463 *
464 * <p> A <i>line terminator</i> is a one- or two-character sequence that marks
465 * the end of a line of the input character sequence. The following are
466 * recognized as line terminators:
467 *
468 * <ul>
469 *
470 * <li> A newline (line feed) character ({@code '\n'}),
471 *
472 * <li> A carriage-return character followed immediately by a newline
473 * character ({@code "\r\n"}),
474 *
475 * <li> A standalone carriage-return character ({@code '\r'}),
476 *
477 * <li> A next-line character (<code>'\u0085'</code>),
478 *
479 * <li> A line-separator character (<code>'\u2028'</code>), or
480 *
481 * <li> A paragraph-separator character (<code>'\u2029'</code>).
482 *
483 * </ul>
484 * <p>If {@link #UNIX_LINES} mode is activated, then the only line terminators
485 * recognized are newline characters.
486 *
487 * <p> The regular expression {@code .} matches any character except a line
488 * terminator unless the {@link #DOTALL} flag is specified.
489 *
490 * <p> By default, the regular expressions {@code ^} and {@code $} ignore
491 * line terminators and only match at the beginning and the end, respectively,
492 * of the entire input sequence. If {@link #MULTILINE} mode is activated then
493 * {@code ^} matches at the beginning of input and after any line terminator
494 * except at the end of input. When in {@link #MULTILINE} mode {@code $}
495 * matches just before a line terminator or the end of the input sequence.
496 *
497 * <h3><a id="cg">Groups and capturing</a></h3>
498 *
499 * <h4><a id="gnumber">Group number</a></h4>
500 * <p> Capturing groups are numbered by counting their opening parentheses from
501 * left to right. In the expression {@code ((A)(B(C)))}, for example, there
502 * are four such groups: </p>
503 *
504 * <blockquote><table>
505 * <caption style="display:none">Capturing group numberings</caption>
506 * <tbody>
507 * <tr><th>1 </th>
508 * <td>{@code ((A)(B(C)))}</td></tr>
509 * <tr><th>2 </th>
510 * <td>{@code (A)}</td></tr>
511 * <tr><th>3 </th>
512 * <td>{@code (B(C))}</td></tr>
513 * <tr><th>4 </th>
514 * <td>{@code (C)}</td></tr>
515 * </tbody>
516 * </table></blockquote>
517 *
518 * <p> Group zero always stands for the entire expression.
519 *
520 * <p> Capturing groups are so named because, during a match, each subsequence
521 * of the input sequence that matches such a group is saved. The captured
522 * subsequence may be used later in the expression, via a back reference, and
523 * may also be retrieved from the matcher once the match operation is complete.
524 *
525 * <h4><a id="groupname">Group name</a></h4>
526 * <p>A capturing group can also be assigned a "name", a {@code named-capturing group},
527 * and then be back-referenced later by the "name". Group names are composed of
528 * the following characters. The first character must be a {@code letter}.
529 *
530 * <ul>
531 * <li> The uppercase letters {@code 'A'} through {@code 'Z'}
532 * (<code>'\u0041'</code> through <code>'\u005a'</code>),
533 * <li> The lowercase letters {@code 'a'} through {@code 'z'}
534 * (<code>'\u0061'</code> through <code>'\u007a'</code>),
535 * <li> The digits {@code '0'} through {@code '9'}
536 * (<code>'\u0030'</code> through <code>'\u0039'</code>),
632 * <li> Ideographic
633 * <li> Letter
634 * <li> Lowercase
635 * <li> Uppercase
636 * <li> Titlecase
637 * <li> Punctuation
638 * <Li> Control
639 * <li> White_Space
640 * <li> Digit
641 * <li> Hex_Digit
642 * <li> Join_Control
643 * <li> Noncharacter_Code_Point
644 * <li> Assigned
645 * </ul>
646 * <p>
647 * The following <b>Predefined Character classes</b> and <b>POSIX character classes</b>
648 * are in conformance with the recommendation of <i>Annex C: Compatibility Properties</i>
649 * of <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Regular Expression
650 * </i></a>, when {@link #UNICODE_CHARACTER_CLASS} flag is specified.
651 *
652 * <table>
653 * <caption style="display:none">predefined and posix character classes in Unicode mode</caption>
654 * <thead>
655 * <tr style="text-align:left">
656 * <th style="text-align:left" id="predef_classes">Classes</th>
657 * <th style="text-align:left" id="predef_matches">Matches</th>
658 * </tr>
659 * </thead>
660 * <tbody>
661 * <tr><td>{@code \p{Lower}}</td>
662 * <td>A lowercase character:{@code \p{IsLowercase}}</td></tr>
663 * <tr><td>{@code \p{Upper}}</td>
664 * <td>An uppercase character:{@code \p{IsUppercase}}</td></tr>
665 * <tr><td>{@code \p{ASCII}}</td>
666 * <td>All ASCII:{@code [\x00-\x7F]}</td></tr>
667 * <tr><td>{@code \p{Alpha}}</td>
668 * <td>An alphabetic character:{@code \p{IsAlphabetic}}</td></tr>
669 * <tr><td>{@code \p{Digit}}</td>
670 * <td>A decimal digit character:{@code \p{IsDigit}}</td></tr>
671 * <tr><td>{@code \p{Alnum}}</td>
672 * <td>An alphanumeric character:{@code [\p{IsAlphabetic}\p{IsDigit}]}</td></tr>
673 * <tr><td>{@code \p{Punct}}</td>
674 * <td>A punctuation character:{@code \p{IsPunctuation}}</td></tr>
675 * <tr><td>{@code \p{Graph}}</td>
676 * <td>A visible character: {@code [^\p{IsWhite_Space}\p{gc=Cc}\p{gc=Cs}\p{gc=Cn}]}</td></tr>
677 * <tr><td>{@code \p{Print}}</td>
678 * <td>A printable character: {@code [\p{Graph}\p{Blank}&&[^\p{Cntrl}]]}</td></tr>
679 * <tr><td>{@code \p{Blank}}</td>
680 * <td>A space or a tab: {@code [\p{IsWhite_Space}&&[^\p{gc=Zl}\p{gc=Zp}\x0a\x0b\x0c\x0d\x85]]}</td></tr>
681 * <tr><td>{@code \p{Cntrl}}</td>
682 * <td>A control character: {@code \p{gc=Cc}}</td></tr>
683 * <tr><td>{@code \p{XDigit}}</td>
684 * <td>A hexadecimal digit: {@code [\p{gc=Nd}\p{IsHex_Digit}]}</td></tr>
685 * <tr><td>{@code \p{Space}}</td>
686 * <td>A whitespace character:{@code \p{IsWhite_Space}}</td></tr>
687 * <tr><td>{@code \d}</td>
688 * <td>A digit: {@code \p{IsDigit}}</td></tr>
689 * <tr><td>{@code \D}</td>
690 * <td>A non-digit: {@code [^\d]}</td></tr>
691 * <tr><td>{@code \s}</td>
692 * <td>A whitespace character: {@code \p{IsWhite_Space}}</td></tr>
693 * <tr><td>{@code \S}</td>
694 * <td>A non-whitespace character: {@code [^\s]}</td></tr>
695 * <tr><td>{@code \w}</td>
696 * <td>A word character: {@code [\p{Alpha}\p{gc=Mn}\p{gc=Me}\p{gc=Mc}\p{Digit}\p{gc=Pc}\p{IsJoin_Control}]}</td></tr>
697 * <tr><td>{@code \W}</td>
698 * <td>A non-word character: {@code [^\w]}</td></tr>
699 * </tbody>
700 * </table>
701 * <p>
702 * <a id="jcc">
703 * Categories that behave like the java.lang.Character
704 * boolean is<i>methodname</i> methods (except for the deprecated ones) are
705 * available through the same <code>\p{</code><i>prop</i><code>}</code> syntax where
706 * the specified property has the name <code>java<i>methodname</i></code></a>.
707 *
708 * <h3> Comparison to Perl 5 </h3>
709 *
710 * <p>The {@code Pattern} engine performs traditional NFA-based matching
711 * with ordered alternation as occurs in Perl 5.
712 *
713 * <p> Perl constructs not supported by this class: </p>
714 *
715 * <ul>
716 * <li><p> The backreference constructs, <code>\g{</code><i>n</i><code>}</code> for
717 * the <i>n</i><sup>th</sup><a href="#cg">capturing group</a> and
1202 *
1203 * <p> When there is a positive-width match at the beginning of the input
1204 * sequence then an empty leading substring is included at the beginning
1205 * of the resulting array. A zero-width match at the beginning however
1206 * never produces such empty leading substring.
1207 *
1208 * <p> The {@code limit} parameter controls the number of times the
1209 * pattern is applied and therefore affects the length of the resulting
1210 * array. If the limit <i>n</i> is greater than zero then the pattern
1211 * will be applied at most <i>n</i> - 1 times, the array's
1212 * length will be no greater than <i>n</i>, and the array's last entry
1213 * will contain all input beyond the last matched delimiter. If <i>n</i>
1214 * is non-positive then the pattern will be applied as many times as
1215 * possible and the array can have any length. If <i>n</i> is zero then
1216 * the pattern will be applied as many times as possible, the array can
1217 * have any length, and trailing empty strings will be discarded.
1218 *
1219 * <p> The input {@code "boo:and:foo"}, for example, yields the following
1220 * results with these parameters:
1221 *
1222 * <blockquote><table>
1223 * <caption>Split examples showing regex, limit, and result</caption>
1224 * <thead>
1225 * <tr><th style="text-align:left"><i>Regex </i></th>
1226 * <th style="text-align:left"><i>Limit </i></th>
1227 * <th style="text-align:left"><i>Result </i></th></tr>
1228 * </thead>
1229 * <tbody>
1230 * <tr><td style="text-align:center">:</td>
1231 * <td style="text-align:center">2</td>
1232 * <td>{@code { "boo", "and:foo" }}</td></tr>
1233 * <tr><td style="text-align:center">:</td>
1234 * <td style="text-align:center">5</td>
1235 * <td>{@code { "boo", "and", "foo" }}</td></tr>
1236 * <tr><td style="text-align:center">:</td>
1237 * <td style="text-align:center">-2</td>
1238 * <td>{@code { "boo", "and", "foo" }}</td></tr>
1239 * <tr><td style="text-align:center">o</td>
1240 * <td style="text-align:center">5</td>
1241 * <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
1242 * <tr><td style="text-align:center">o</td>
1243 * <td style="text-align:center">-2</td>
1244 * <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
1245 * <tr><td style="text-align:center">o</td>
1246 * <td style="text-align:center">0</td>
1247 * <td>{@code { "b", "", ":and:f" }}</td></tr>
1248 * </tbody>
1249 * </table></blockquote>
1250 *
1251 * @param input
1252 * The character sequence to be split
1253 *
1254 * @param limit
1255 * The result threshold, as described above
1256 *
1257 * @return The array of strings computed by splitting the input
1258 * around matches of this pattern
1259 */
1260 public String[] split(CharSequence input, int limit) {
1261 int index = 0;
1262 boolean matchLimited = limit > 0;
1263 ArrayList<String> matchList = new ArrayList<>();
1264 Matcher m = matcher(input);
1265
1266 // Add segments before each match found
1267 while(m.find()) {
1268 if (!matchLimited || matchList.size() < limit - 1) {
1269 if (index == 0 && index == m.start() && m.start() == m.end()) {
1293 // Construct result
1294 int resultSize = matchList.size();
1295 if (limit == 0)
1296 while (resultSize > 0 && matchList.get(resultSize-1).equals(""))
1297 resultSize--;
1298 String[] result = new String[resultSize];
1299 return matchList.subList(0, resultSize).toArray(result);
1300 }
1301
1302 /**
1303 * Splits the given input sequence around matches of this pattern.
1304 *
1305 * <p> This method works as if by invoking the two-argument {@link
1306 * #split(java.lang.CharSequence, int) split} method with the given input
1307 * sequence and a limit argument of zero. Trailing empty strings are
1308 * therefore not included in the resulting array. </p>
1309 *
1310 * <p> The input {@code "boo:and:foo"}, for example, yields the following
1311 * results with these expressions:
1312 *
1313 * <blockquote><table>
1314 * <caption style="display:none">Split examples showing regex and result</caption>
1315 * <thead>
1316 * <tr><th style="text-align:left"><i>Regex </i></th>
1317 * <th style="text-align:left"><i>Result</i></th></tr>
1318 * </thead>
1319 * <tbody>
1320 * <tr><td style="text-align:center">:</td>
1321 * <td>{@code { "boo", "and", "foo" }}</td></tr>
1322 * <tr><td style="text-align:center">o</td>
1323 * <td>{@code { "b", "", ":and:f" }}</td></tr>
1324 * </tbody>
1325 * </table></blockquote>
1326 *
1327 *
1328 * @param input
1329 * The character sequence to be split
1330 *
1331 * @return The array of strings computed by splitting the input
1332 * around matches of this pattern
1333 */
1334 public String[] split(CharSequence input) {
1335 return split(input, 0);
1336 }
1337
1338 /**
1339 * Returns a literal pattern {@code String} for the specified
1340 * {@code String}.
1341 *
1342 * <p>This method produces a {@code String} that can be used to
1343 * create a {@code Pattern} that would match the string
1344 * {@code s} as if it were a literal pattern.</p> Metacharacters
1345 * or escape sequences in the input sequence will be given no special
|
64 * <p> A {@link #matches matches} method is defined by this class as a
65 * convenience for when a regular expression is used just once. This method
66 * compiles an expression and matches an input sequence against it in a single
67 * invocation. The statement
68 *
69 * <blockquote><pre>
70 * boolean b = Pattern.matches("a*b", "aaaaab");</pre></blockquote>
71 *
72 * is equivalent to the three statements above, though for repeated matches it
73 * is less efficient since it does not allow the compiled pattern to be reused.
74 *
75 * <p> Instances of this class are immutable and are safe for use by multiple
76 * concurrent threads. Instances of the {@link Matcher} class are not safe for
77 * such use.
78 *
79 *
80 * <h3><a id="sum">Summary of regular-expression constructs</a></h3>
81 *
82 * <table class="borderless">
83 * <caption style="display:none">Regular expression constructs, and what they match</caption>
84 * <thead style="text-align:left">
85 * <tr>
86 * <th id="construct">Construct</th>
87 * <th id="matches">Matches</th>
88 * </tr>
89 * </thead>
90 * <tbody style="text-align:left">
91 *
92 * <tr><th colspan="2" style="padding-top:20px" id="characters">Characters</th></tr>
93 *
94 * <tr><th style="vertical-align:top; font-weight: normal" id="x"><i>x</i></th>
95 * <td headers="matches characters x">The character <i>x</i></td></tr>
96 * <tr><th style="vertical-align:top; font-weight: normal" id="backslash">{@code \\}</th>
97 * <td headers="matches characters backslash">The backslash character</td></tr>
98 * <tr><th style="vertical-align:top; font-weight: normal" id="octal_n">{@code \0}<i>n</i></th>
99 * <td headers="matches characters octal_n">The character with octal value {@code 0}<i>n</i>
100 * (0 {@code <=} <i>n</i> {@code <=} 7)</td></tr>
101 * <tr><th style="vertical-align:top; font-weight: normal" id="octal_nn">{@code \0}<i>nn</i></th>
102 * <td headers="matches characters octal_nn">The character with octal value {@code 0}<i>nn</i>
103 * (0 {@code <=} <i>n</i> {@code <=} 7)</td></tr>
104 * <tr><th style="vertical-align:top; font-weight: normal" id="octal_nnn">{@code \0}<i>mnn</i></th>
105 * <td headers="matches characters octal_nnn">The character with octal value {@code 0}<i>mnn</i>
106 * (0 {@code <=} <i>m</i> {@code <=} 3,
107 * 0 {@code <=} <i>n</i> {@code <=} 7)</td></tr>
108 * <tr><th style="vertical-align:top; font-weight: normal" id="hex_hh">{@code \x}<i>hh</i></th>
109 * <td headers="matches characters hex_hh">The character with hexadecimal value {@code 0x}<i>hh</i></td></tr>
110 * <tr><th style="vertical-align:top; font-weight: normal" id="hex_hhhh"><code>\u</code><i>hhhh</i></th>
111 * <td headers="matches characters hex_hhhh">The character with hexadecimal value {@code 0x}<i>hhhh</i></td></tr>
112 * <tr><th style="vertical-align:top; font-weight: normal" id="hex_h_h"><code>\x</code><i>{h...h}</i></th>
113 * <td headers="matches characters hex_h_h">The character with hexadecimal value {@code 0x}<i>h...h</i>
114 * ({@link java.lang.Character#MIN_CODE_POINT Character.MIN_CODE_POINT}
115 * <= {@code 0x}<i>h...h</i> <=
116 * {@link java.lang.Character#MAX_CODE_POINT Character.MAX_CODE_POINT})</td></tr>
117 * <tr><th style="vertical-align:top; font-weight: normal" id="unicode_name"><code>\N{</code><i>name</i><code>}</code></th>
118 * <td headers="matches characters unicode_name">The character with Unicode character name <i>'name'</i></td></tr>
119 * <tr><th style="vertical-align:top; font-weight:normal" id="tab">{@code \t}</th>
120 * <td headers="matches characters tab">The tab character (<code>'\u0009'</code>)</td></tr>
121 * <tr><th style="vertical-align:top; font-weight:normal" id="newline">{@code \n}</th>
122 * <td headers="matches characters newline">The newline (line feed) character (<code>'\u000A'</code>)</td></tr>
123 * <tr><th style="vertical-align:top; font-weight:normal" id="return">{@code \r}</th>
124 * <td headers="matches characters return">The carriage-return character (<code>'\u000D'</code>)</td></tr>
125 * <tr><th style="vertical-align:top; font-weight:normal" id="form_feed">{@code \f}</th>
126 * <td headers="matches characters form_feed">The form-feed character (<code>'\u000C'</code>)</td></tr>
127 * <tr><th style="vertical-align:top; font-weight:normal" id="bell">{@code \a}</th>
128 * <td headers="matches characters bell">The alert (bell) character (<code>'\u0007'</code>)</td></tr>
129 * <tr><th style="vertical-align:top; font-weight:normal" id="escape">{@code \e}</th>
130 * <td headers="matches characters escape">The escape character (<code>'\u001B'</code>)</td></tr>
131 * <tr><th style="vertical-align:top; font-weight:normal" id="ctrl_x">{@code \c}<i>x</i></th>
132 * <td headers="matches characters ctrl_x">The control character corresponding to <i>x</i></td></tr>
133 *
134 * <tr><th colspan="2" style="padding-top:20px" id="classes">Character classes</th></tr>
135 *
136 * <tr><th style="vertical-align:top; font-weight:normal" id="simple">{@code [abc]}</th>
137 * <td headers="matches classes simple">{@code a}, {@code b}, or {@code c} (simple class)</td></tr>
138 * <tr><th style="vertical-align:top; font-weight:normal" id="negation">{@code [^abc]}</th>
139 * <td headers="matches classes negation">Any character except {@code a}, {@code b}, or {@code c} (negation)</td></tr>
140 * <tr><th style="vertical-align:top; font-weight:normal" id="range">{@code [a-zA-Z]}</th>
141 * <td headers="matches classes range">{@code a} through {@code z}
142 * or {@code A} through {@code Z}, inclusive (range)</td></tr>
143 * <tr><th style="vertical-align:top; font-weight:normal" id="union">{@code [a-d[m-p]]}</th>
144 * <td headers="matches classes union">{@code a} through {@code d},
145 * or {@code m} through {@code p}: {@code [a-dm-p]} (union)</td></tr>
146 * <tr><th style="vertical-align:top; font-weight:normal" id="intersection">{@code [a-z&&[def]]}</th>
147 * <td headers="matches classes intersection">{@code d}, {@code e}, or {@code f} (intersection)</tr>
148 * <tr><th style="vertical-align:top; font-weight:normal" id="subtraction1">{@code [a-z&&[^bc]]}</th>
149 * <td headers="matches classes subtraction1">{@code a} through {@code z},
150 * except for {@code b} and {@code c}: {@code [ad-z]} (subtraction)</td></tr>
151 * <tr><th style="vertical-align:top; font-weight:normal" id="subtraction2">{@code [a-z&&[^m-p]]}</th>
152 * <td headers="matches classes subtraction2">{@code a} through {@code z},
153 * and not {@code m} through {@code p}: {@code [a-lq-z]}(subtraction)</td></tr>
154 *
155 * <tr><th colspan="2" style="padding-top:20px" id="predef">Predefined character classes</th></tr>
156 *
157 * <tr><th style="vertical-align:top; font-weight:normal" id="any">{@code .}</th>
158 * <td headers="matches predef any">Any character (may or may not match <a href="#lt">line terminators</a>)</td></tr>
159 * <tr><th style="vertical-align:top; font-weight:normal" id="digit">{@code \d}</th>
160 * <td headers="matches predef digit">A digit: {@code [0-9]}</td></tr>
161 * <tr><th style="vertical-align:top; font-weight:normal" id="non_digit">{@code \D}</th>
162 * <td headers="matches predef non_digit">A non-digit: {@code [^0-9]}</td></tr>
163 * <tr><th style="vertical-align:top; font-weight:normal" id="horiz_white">{@code \h}</th>
164 * <td headers="matches predef horiz_white">A horizontal whitespace character:
165 * <code>[ \t\xA0\u1680\u180e\u2000-\u200a\u202f\u205f\u3000]</code></td></tr>
166 * <tr><th style="vertical-align:top; font-weight:normal" id="non_horiz_white">{@code \H}</th>
167 * <td headers="matches predef non_horiz_white">A non-horizontal whitespace character: {@code [^\h]}</td></tr>
168 * <tr><th style="vertical-align:top; font-weight:normal" id="white">{@code \s}</th>
169 * <td headers="matches predef white">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
170 * <tr><th style="vertical-align:top; font-weight:normal" id="non_white">{@code \S}</th>
171 * <td headers="matches predef non_white">A non-whitespace character: {@code [^\s]}</td></tr>
172 * <tr><th style="vertical-align:top; font-weight:normal" id="vert_white">{@code \v}</th>
173 * <td headers="matches predef vert_white">A vertical whitespace character: <code>[\n\x0B\f\r\x85\u2028\u2029]</code>
174 * </td></tr>
175 * <tr><th style="vertical-align:top; font-weight:normal" id="non_vert_white">{@code \V}</th>
176 * <td headers="matches predef non_vert_white">A non-vertical whitespace character: {@code [^\v]}</td></tr>
177 * <tr><th style="vertical-align:top; font-weight:normal" id="word">{@code \w}</th>
178 * <td headers="matches predef word">A word character: {@code [a-zA-Z_0-9]}</td></tr>
179 * <tr><th style="vertical-align:top; font-weight:normal" id="non_word">{@code \W}</th>
180 * <td headers="matches predef non_word">A non-word character: {@code [^\w]}</td></tr>
181 *
182 * <tr><th colspan="2" style="padding-top:20px" id="posix"><b>POSIX character classes (US-ASCII only)</b></th></tr>
183 *
184 * <tr><th style="vertical-align:top; font-weight:normal" id="Lower">{@code \p{Lower}}</th>
185 * <td headers="matches posix Lower">A lower-case alphabetic character: {@code [a-z]}</td></tr>
186 * <tr><th style="vertical-align:top; font-weight:normal" id="Upper">{@code \p{Upper}}</th>
187 * <td headers="matches posix Upper">An upper-case alphabetic character:{@code [A-Z]}</td></tr>
188 * <tr><th style="vertical-align:top; font-weight:normal" id="ASCII">{@code \p{ASCII}}</th>
189 * <td headers="matches posix ASCII">All ASCII:{@code [\x00-\x7F]}</td></tr>
190 * <tr><th style="vertical-align:top; font-weight:normal" id="Alpha">{@code \p{Alpha}}</th>
191 * <td headers="matches posix Alpha">An alphabetic character:{@code [\p{Lower}\p{Upper}]}</td></tr>
192 * <tr><th style="vertical-align:top; font-weight:normal" id="Digit">{@code \p{Digit}}</th>
193 * <td headers="matches posix Digit">A decimal digit: {@code [0-9]}</td></tr>
194 * <tr><th style="vertical-align:top; font-weight:normal" id="Alnum">{@code \p{Alnum}}</th>
195 * <td headers="matches posix Alnum">An alphanumeric character:{@code [\p{Alpha}\p{Digit}]}</td></tr>
196 * <tr><th style="vertical-align:top; font-weight:normal" id="Punct">{@code \p{Punct}}</th>
197 * <td headers="matches posix Punct">Punctuation: One of {@code !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~}</td></tr>
198 * <!-- {@code [\!"#\$%&'\(\)\*\+,\-\./:;\<=\>\?@\[\\\]\^_`\{\|\}~]}
199 * {@code [\X21-\X2F\X31-\X40\X5B-\X60\X7B-\X7E]} -->
200 * <tr><th style="vertical-align:top; font-weight:normal" id="Graph">{@code \p{Graph}}</th>
201 * <td headers="matches posix Graph">A visible character: {@code [\p{Alnum}\p{Punct}]}</td></tr>
202 * <tr><th style="vertical-align:top; font-weight:normal" id="Print">{@code \p{Print}}</th>
203 * <td headers="matches posix Print">A printable character: {@code [\p{Graph}\x20]}</td></tr>
204 * <tr><th style="vertical-align:top; font-weight:normal" id="Blank">{@code \p{Blank}}</th>
205 * <td headers="matches posix Blank">A space or a tab: {@code [ \t]}</td></tr>
206 * <tr><th style="vertical-align:top; font-weight:normal" id="Cntrl">{@code \p{Cntrl}}</th>
207 * <td headers="matches posix Cntrl">A control character: {@code [\x00-\x1F\x7F]}</td></tr>
208 * <tr><th style="vertical-align:top; font-weight:normal" id="XDigit">{@code \p{XDigit}}</th>
209 * <td headers="matches posix XDigit">A hexadecimal digit: {@code [0-9a-fA-F]}</td></tr>
210 * <tr><th style="vertical-align:top; font-weight:normal" id="Space">{@code \p{Space}}</th>
211 * <td headers="matches posix Space">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
212 *
213 * <tr><th colspan="2" style="padding-top:20px" id="java">java.lang.Character classes (simple <a href="#jcc">java character type</a>)</th></tr>
214 *
215 * <tr><th style="vertical-align:top; font-weight:normal" id="javaLowerCase">{@code \p{javaLowerCase}}</th>
216 * <td headers="matches java javaLowerCase">Equivalent to java.lang.Character.isLowerCase()</td></tr>
217 * <tr><th style="vertical-align:top; font-weight:normal" id="javaUpperCase">{@code \p{javaUpperCase}}</th>
218 * <td headers="matches java javaUpperCase">Equivalent to java.lang.Character.isUpperCase()</td></tr>
219 * <tr><th style="vertical-align:top; font-weight:normal" id="javaWhitespace">{@code \p{javaWhitespace}}</th>
220 * <td headers="matches java javaWhitespace">Equivalent to java.lang.Character.isWhitespace()</td></tr>
221 * <tr><th style="vertical-align:top; font-weight:normal" id="javaMirrored">{@code \p{javaMirrored}}</th>
222 * <td headers="matches java javaMirrored">Equivalent to java.lang.Character.isMirrored()</td></tr>
223 *
224 * <tr><th colspan="2" style="padding-top:20px" id="unicode">Classes for Unicode scripts, blocks, categories and binary properties</th></tr>
225 *
226 * <tr><th style="vertical-align:top; font-weight:normal" id="IsLatin">{@code \p{IsLatin}}</th>
227 * <td headers="matches unicode IsLatin">A Latin script character (<a href="#usc">script</a>)</td></tr>
228 * <tr><th style="vertical-align:top; font-weight:normal" id="InGreek">{@code \p{InGreek}}</th>
229 * <td headers="matches unicode InGreek">A character in the Greek block (<a href="#ubc">block</a>)</td></tr>
230 * <tr><th style="vertical-align:top; font-weight:normal" id="Lu">{@code \p{Lu}}</th>
231 * <td headers="matches unicode Lu">An uppercase letter (<a href="#ucc">category</a>)</td></tr>
232 * <tr><th style="vertical-align:top; font-weight:normal" id="IsAlphabetic">{@code \p{IsAlphabetic}}</th>
233 * <td headers="matches unicode IsAlphabetic">An alphabetic character (<a href="#ubpc">binary property</a>)</td></tr>
234 * <tr><th style="vertical-align:top; font-weight:normal" id="Sc">{@code \p{Sc}}</th>
235 * <td headers="matches unicode Sc">A currency symbol</td></tr>
236 * <tr><th style="vertical-align:top; font-weight:normal" id="not_InGreek">{@code \P{InGreek}}</th>
237 * <td headers="matches unicode not_InGreek">Any character except one in the Greek block (negation)</td></tr>
238 * <tr><th style="vertical-align:top; font-weight:normal" id="not_uppercase">{@code [\p{L}&&[^\p{Lu}]]}</th>
239 * <td headers="matches unicode not_uppercase">Any letter except an uppercase letter (subtraction)</td></tr>
240 *
241 * <tr><th colspan="2" style="padding-top:20px" id="bounds">Boundary matchers</th></tr>
242 *
243 * <tr><th style="vertical-align:top; font-weight:normal" id="begin_line">{@code ^}</th>
244 * <td headers="matches bounds begin_line">The beginning of a line</td></tr>
245 * <tr><th style="vertical-align:top; font-weight:normal" id="end_line">{@code $}</th>
246 * <td headers="matches bounds end_line">The end of a line</td></tr>
247 * <tr><th style="vertical-align:top; font-weight:normal" id="word_boundary">{@code \b}</th>
248 * <td headers="matches bounds word_boundary">A word boundary</td></tr>
249 * <tr><th style="vertical-align:top; font-weight:normal" id="grapheme_cluster_boundary">{@code \b{g}}</th>
250 * <td headers="matches bounds grapheme_cluster_boundary">A Unicode extended grapheme cluster boundary</td></tr>
251 * <tr><th style="vertical-align:top; font-weight:normal" id="non_word_boundary">{@code \B}</th>
252 * <td headers="matches bounds non_word_boundary">A non-word boundary</td></tr>
253 * <tr><th style="vertical-align:top; font-weight:normal" id="begin_input">{@code \A}</th>
254 * <td headers="matches bounds begin_input">The beginning of the input</td></tr>
255 * <tr><th style="vertical-align:top; font-weight:normal" id="end_prev_match">{@code \G}</th>
256 * <td headers="matches bounds end_prev_match">The end of the previous match</td></tr>
257 * <tr><th style="vertical-align:top; font-weight:normal" id="end_input_except_term">{@code \Z}</th>
258 * <td headers="matches bounds end_input_except_term">The end of the input but for the final
259 * <a href="#lt">terminator</a>, if any</td></tr>
260 * <tr><th style="vertical-align:top; font-weight:normal" id="end_input">{@code \z}</th>
261 * <td headers="matches bounds end_input">The end of the input</td></tr>
262 *
263 * <tr><th colspan="2" style="padding-top:20px" id="linebreak">Linebreak matcher</th></tr>
264 *
265 * <tr><th style="vertical-align:top; font-weight:normal" id="any_unicode_linebreak">{@code \R}</th>
266 * <td headers="matches linebreak any_unicode_linebreak">Any Unicode linebreak sequence, is equivalent to
267 * <code>\u000D\u000A|[\u000A\u000B\u000C\u000D\u0085\u2028\u2029]
268 * </code></td></tr>
269 *
270 * <tr><th colspan="2" style="padding-top:20px" id="grapheme">Unicode Extended Grapheme matcher</th></tr>
271 *
272 * <tr><th style="vertical-align:top; font-weight:normal" id="grapheme_any">{@code \X}</th>
273 * <td headers="matches grapheme grapheme_any">Any Unicode extended grapheme cluster</td></tr>
274 *
275 * <tr><th colspan="2" style="padding-top:20px" id="greedy">Greedy quantifiers</th></tr>
276 *
277 * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_once_or_not"><i>X</i>{@code ?}</th>
278 * <td headers="matches greedy greedy_once_or_not"><i>X</i>, once or not at all</td></tr>
279 * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_zero_or_more"><i>X</i>{@code *}</th>
280 * <td headers="matches greedy greedy_zero_or_more"><i>X</i>, zero or more times</td></tr>
281 * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_one_or_more"><i>X</i>{@code +}</th>
282 * <td headers="matches greedy greedy_one_or_more"><i>X</i>, one or more times</td></tr>
283 * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_exactly"><i>X</i><code>{</code><i>n</i><code>}</code></th>
284 * <td headers="matches greedy greedy_exactly"><i>X</i>, exactly <i>n</i> times</td></tr>
285 * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_at_least"><i>X</i><code>{</code><i>n</i>{@code ,}}</th>
286 * <td headers="matches greedy greedy_at_least"><i>X</i>, at least <i>n</i> times</td></tr>
287 * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_at_least_up_to"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}</code></th>
288 * <td headers="matches greedy greedy_at_least_up_to"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
289 *
290 * <tr><th colspan="2" style="padding-top:20px" id="reluc">Reluctant quantifiers</th></tr>
291 *
292 * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_once_or_not"><i>X</i>{@code ??}</th>
293 * <td headers="matches reluc reluc_once_or_not"><i>X</i>, once or not at all</td></tr>
294 * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_zero_or_more"><i>X</i>{@code *?}</th>
295 * <td headers="matches reluc reluc_zero_or_more"><i>X</i>, zero or more times</td></tr>
296 * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_one_or_more"><i>X</i>{@code +?}</th>
297 * <td headers="matches reluc reluc_one_or_more"><i>X</i>, one or more times</td></tr>
298 * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_exactly"><i>X</i><code>{</code><i>n</i><code>}?</code></th>
299 * <td headers="matches reluc reluc_exactly"><i>X</i>, exactly <i>n</i> times</td></tr>
300 * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_at_least"><i>X</i><code>{</code><i>n</i><code>,}?</code></th>
301 * <td headers="matches reluc reluc_at_least"><i>X</i>, at least <i>n</i> times</td></tr>
302 * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_at_least_up_to"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}?</code></th>
303 * <td headers="matches reluc reluc_at_least_up_to"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
304 *
305 * <tr><th colspan="2" style="padding-top:20px" id="poss">Possessive quantifiers</th></tr>
306 *
307 * <tr><th style="vertical-align:top; font-weight:normal" id="poss_once_or_not"><i>X</i>{@code ?+}</th>
308 * <td headers="matches poss poss_once_or_not"><i>X</i>, once or not at all</td></tr>
309 * <tr><th style="vertical-align:top; font-weight:normal" id="poss_zero_or_more"><i>X</i>{@code *+}</th>
310 * <td headers="matches poss poss_zero_or_more"><i>X</i>, zero or more times</td></tr>
311 * <tr><th style="vertical-align:top; font-weight:normal" id="poss_one_or_more"><i>X</i>{@code ++}</th>
312 * <td headers="matches poss poss_one_or_more"><i>X</i>, one or more times</td></tr>
313 * <tr><th style="vertical-align:top; font-weight:normal" id="poss_exactly"><i>X</i><code>{</code><i>n</i><code>}+</code></th>
314 * <td headers="matches poss poss_exactly"><i>X</i>, exactly <i>n</i> times</td></tr>
315 * <tr><th style="vertical-align:top; font-weight:normal" id="poss_at_least"><i>X</i><code>{</code><i>n</i><code>,}+</code></th>
316 * <td headers="matches poss poss_at_least"><i>X</i>, at least <i>n</i> times</td></tr>
317 * <tr><th style="vertical-align:top; font-weight:normal" id="poss_at_least_up_to"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}+</code></th>
318 * <td headers="matches poss poss_at_least_up_to"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
319 *
320 * <tr><th colspan="2" style="padding-top:20px" id="logical">Logical operators</th></tr>
321 *
322 * <tr><th style="vertical-align:top; font-weight:normal" id="concat"><i>XY</i></th>
323 * <td headers="matches logical concat"><i>X</i> followed by <i>Y</i></td></tr>
324 * <tr><th style="vertical-align:top; font-weight:normal" id="alternate"><i>X</i>{@code |}<i>Y</i></th>
325 * <td headers="matches logical alternate">Either <i>X</i> or <i>Y</i></td></tr>
326 * <tr><th style="vertical-align:top; font-weight:normal" id="group">{@code (}<i>X</i>{@code )}</th>
327 * <td headers="matches logical group">X, as a <a href="#cg">capturing group</a></td></tr>
328 *
329 * <tr><th colspan="2" style="padding-top:20px" id="backref">Back references</th></tr>
330 *
331 * <tr><th style="vertical-align:top; font-weight:normal" id="back_nth">{@code \}<i>n</i></th>
332 * <td headers="matches backref back_nth">Whatever the <i>n</i><sup>th</sup>
333 * <a href="#cg">capturing group</a> matched</td></tr>
334 * <tr><th style="vertical-align:top; font-weight:normal" id="back_named">{@code \}<i>k</i><<i>name</i>></th>
335 * <td headers="matches backref back_named">Whatever the
336 * <a href="#groupname">named-capturing group</a> "name" matched</td></tr>
337 *
338 * <tr><th colspan="2" style="padding-top:20px" id="quote">Quotation</th></tr>
339 *
340 * <tr><th style="vertical-align:top; font-weight:normal" id="quote_follow">{@code \}</th>
341 * <td headers="matches quote quote_follow">Nothing, but quotes the following character</td></tr>
342 * <tr><th style="vertical-align:top; font-weight:normal" id="quote_begin">{@code \Q}</th>
343 * <td headers="matches quote quote_begin">Nothing, but quotes all characters until {@code \E}</td></tr>
344 * <tr><th style="vertical-align:top; font-weight:normal" id="quote_end">{@code \E}</th>
345 * <td headers="matches quote quote_end">Nothing, but ends quoting started by {@code \Q}</td></tr>
346 * <!-- Metachars: !$()*+.<>?[\]^{|} -->
347 *
348 * <tr><th colspan="2" style="padding-top:20px" id="special">Special constructs (named-capturing and non-capturing)</th></tr>
349 *
350 * <tr><th style="vertical-align:top; font-weight:normal" id="named_group"><code>(?<<a href="#groupname">name</a>></code><i>X</i>{@code )}</th>
351 * <td headers="matches special named_group"><i>X</i>, as a named-capturing group</td></tr>
352 * <tr><th style="vertical-align:top; font-weight:normal" id="non_capture_group">{@code (?:}<i>X</i>{@code )}</th>
353 * <td headers="matches special non_capture_group"><i>X</i>, as a non-capturing group</td></tr>
354 * <tr><th style="vertical-align:top; font-weight:normal" id="flags"><code>(?idmsuxU-idmsuxU) </code></th>
355 * <td headers="matches special flags">Nothing, but turns match flags <a href="#CASE_INSENSITIVE">i</a>
356 * <a href="#UNIX_LINES">d</a> <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a>
357 * <a href="#UNICODE_CASE">u</a> <a href="#COMMENTS">x</a> <a href="#UNICODE_CHARACTER_CLASS">U</a>
358 * on - off</td></tr>
359 * <tr><th style="vertical-align:top; font-weight:normal" id="non_capture_group_flags"><code>(?idmsux-idmsux:</code><i>X</i>{@code )} </th>
360 * <td headers="matches special non_capture_group_flags"><i>X</i>, as a <a href="#cg">non-capturing group</a> with the
361 * given flags <a href="#CASE_INSENSITIVE">i</a> <a href="#UNIX_LINES">d</a>
362 * <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a> <a href="#UNICODE_CASE">u</a >
363 * <a href="#COMMENTS">x</a> on - off</td></tr>
364 * <tr><th style="vertical-align:top; font-weight:normal" id="pos_lookahead">{@code (?=}<i>X</i>{@code )}</th>
365 * <td headers="matches special pos_lookahead"><i>X</i>, via zero-width positive lookahead</td></tr>
366 * <tr><th style="vertical-align:top; font-weight:normal" id="neg_lookahead">{@code (?!}<i>X</i>{@code )}</th>
367 * <td headers="matches special neg_lookahead"><i>X</i>, via zero-width negative lookahead</td></tr>
368 * <tr><th style="vertical-align:top; font-weight:normal" id="pos_lookbehind">{@code (?<=}<i>X</i>{@code )}</th>
369 * <td headers="matches special pos_lookbehind"><i>X</i>, via zero-width positive lookbehind</td></tr>
370 * <tr><th style="vertical-align:top; font-weight:normal" id="neg_lookbehind">{@code (?<!}<i>X</i>{@code )}</th>
371 * <td headers="matches special neg_lookbehind"><i>X</i>, via zero-width negative lookbehind</td></tr>
372 * <tr><th style="vertical-align:top; font-weight:normal" id="indep_non_capture_group">{@code (?>}<i>X</i>{@code )}</th>
373 * <td headers="matches special indep_non_capture_group"><i>X</i>, as an independent, non-capturing group</td></tr>
374 *
375 * </tbody>
376 * </table>
377 *
378 * <hr>
379 *
380 *
381 * <h3><a id="bs">Backslashes, escapes, and quoting</a></h3>
382 *
383 * <p> The backslash character ({@code '\'}) serves to introduce escaped
384 * constructs, as defined in the table above, as well as to quote characters
385 * that otherwise would be interpreted as unescaped constructs. Thus the
386 * expression {@code \\} matches a single backslash and <code>\{</code> matches a
387 * left brace.
388 *
389 * <p> It is an error to use a backslash prior to any alphabetic character that
390 * does not denote an escaped construct; these are reserved for future
391 * extensions to the regular-expression language. A backslash may be used
392 * prior to a non-alphabetic character regardless of whether that character is
393 * part of an unescaped construct.
402 * <code>"\b"</code>, for example, matches a single backspace character when
403 * interpreted as a regular expression, while {@code "\\b"} matches a
404 * word boundary. The string literal {@code "\(hello\)"} is illegal
405 * and leads to a compile-time error; in order to match the string
406 * {@code (hello)} the string literal {@code "\\(hello\\)"}
407 * must be used.
408 *
409 * <h3><a id="cc">Character Classes</a></h3>
410 *
411 * <p> Character classes may appear within other character classes, and
412 * may be composed by the union operator (implicit) and the intersection
413 * operator ({@code &&}).
414 * The union operator denotes a class that contains every character that is
415 * in at least one of its operand classes. The intersection operator
416 * denotes a class that contains every character that is in both of its
417 * operand classes.
418 *
419 * <p> The precedence of character-class operators is as follows, from
420 * highest to lowest:
421 *
422 * <table class="striped" style="margin-left: 2em;">
423 * <caption style="display:none">Precedence of character class operators.</caption>
424 * <thead>
425 * <tr><th scope="col">Precedence<th scope="col">Name<th scope="col">Example
426 * </thead>
427 * <tbody>
428 * <tr><th scope="row">1</th>
429 * <td>Literal escape </td>
430 * <td>{@code \x}</td></tr>
431 * <tr><th scope="row">2</th>
432 * <td>Grouping</td>
433 * <td>{@code [...]}</td></tr>
434 * <tr><th scope="row">3</th>
435 * <td>Range</td>
436 * <td>{@code a-z}</td></tr>
437 * <tr><th scope="row">4</th>
438 * <td>Union</td>
439 * <td>{@code [a-e][i-u]}</td></tr>
440 * <tr><th scope="row">5</th>
441 * <td>Intersection</td>
442 * <td>{@code [a-z&&[aeiou]]}</td></tr>
443 * </tbody>
444 * </table>
445 *
446 * <p> Note that a different set of metacharacters are in effect inside
447 * a character class than outside a character class. For instance, the
448 * regular expression {@code .} loses its special meaning inside a
449 * character class, while the expression {@code -} becomes a range
450 * forming metacharacter.
451 *
452 * <h3><a id="lt">Line terminators</a></h3>
453 *
454 * <p> A <i>line terminator</i> is a one- or two-character sequence that marks
455 * the end of a line of the input character sequence. The following are
456 * recognized as line terminators:
457 *
458 * <ul>
459 *
460 * <li> A newline (line feed) character ({@code '\n'}),
461 *
462 * <li> A carriage-return character followed immediately by a newline
463 * character ({@code "\r\n"}),
464 *
465 * <li> A standalone carriage-return character ({@code '\r'}),
466 *
467 * <li> A next-line character (<code>'\u0085'</code>),
468 *
469 * <li> A line-separator character (<code>'\u2028'</code>), or
470 *
471 * <li> A paragraph-separator character (<code>'\u2029'</code>).
472 *
473 * </ul>
474 * <p>If {@link #UNIX_LINES} mode is activated, then the only line terminators
475 * recognized are newline characters.
476 *
477 * <p> The regular expression {@code .} matches any character except a line
478 * terminator unless the {@link #DOTALL} flag is specified.
479 *
480 * <p> By default, the regular expressions {@code ^} and {@code $} ignore
481 * line terminators and only match at the beginning and the end, respectively,
482 * of the entire input sequence. If {@link #MULTILINE} mode is activated then
483 * {@code ^} matches at the beginning of input and after any line terminator
484 * except at the end of input. When in {@link #MULTILINE} mode {@code $}
485 * matches just before a line terminator or the end of the input sequence.
486 *
487 * <h3><a id="cg">Groups and capturing</a></h3>
488 *
489 * <h4><a id="gnumber">Group number</a></h4>
490 * <p> Capturing groups are numbered by counting their opening parentheses from
491 * left to right. In the expression {@code ((A)(B(C)))}, for example, there
492 * are four such groups: </p>
493 *
494 * <ol style="margin-left:2em;">
495 * <li> {@code ((A)(B(C)))}
496 * <li> {@code (A)}
497 * <li> {@code (B(C))}
498 * <li> {@code (C)}
499 * </ol>
500 *
501 * <p> Group zero always stands for the entire expression.
502 *
503 * <p> Capturing groups are so named because, during a match, each subsequence
504 * of the input sequence that matches such a group is saved. The captured
505 * subsequence may be used later in the expression, via a back reference, and
506 * may also be retrieved from the matcher once the match operation is complete.
507 *
508 * <h4><a id="groupname">Group name</a></h4>
509 * <p>A capturing group can also be assigned a "name", a {@code named-capturing group},
510 * and then be back-referenced later by the "name". Group names are composed of
511 * the following characters. The first character must be a {@code letter}.
512 *
513 * <ul>
514 * <li> The uppercase letters {@code 'A'} through {@code 'Z'}
515 * (<code>'\u0041'</code> through <code>'\u005a'</code>),
516 * <li> The lowercase letters {@code 'a'} through {@code 'z'}
517 * (<code>'\u0061'</code> through <code>'\u007a'</code>),
518 * <li> The digits {@code '0'} through {@code '9'}
519 * (<code>'\u0030'</code> through <code>'\u0039'</code>),
615 * <li> Ideographic
616 * <li> Letter
617 * <li> Lowercase
618 * <li> Uppercase
619 * <li> Titlecase
620 * <li> Punctuation
621 * <Li> Control
622 * <li> White_Space
623 * <li> Digit
624 * <li> Hex_Digit
625 * <li> Join_Control
626 * <li> Noncharacter_Code_Point
627 * <li> Assigned
628 * </ul>
629 * <p>
630 * The following <b>Predefined Character classes</b> and <b>POSIX character classes</b>
631 * are in conformance with the recommendation of <i>Annex C: Compatibility Properties</i>
632 * of <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Regular Expression
633 * </i></a>, when {@link #UNICODE_CHARACTER_CLASS} flag is specified.
634 *
635 * <table class="striped">
636 * <caption style="display:none">predefined and posix character classes in Unicode mode</caption>
637 * <thead>
638 * <tr>
639 * <th scope="col" id="predef_classes">Classes</th>
640 * <th scope="col" id="predef_matches">Matches</th>
641 * </tr>
642 * </thead>
643 * <tbody>
644 * <tr><th scope="row">{@code \p{Lower}}</th>
645 * <td>A lowercase character:{@code \p{IsLowercase}}</td></tr>
646 * <tr><th scope="row">{@code \p{Upper}}</th>
647 * <td>An uppercase character:{@code \p{IsUppercase}}</td></tr>
648 * <tr><th scope="row">{@code \p{ASCII}}</th>
649 * <td>All ASCII:{@code [\x00-\x7F]}</td></tr>
650 * <tr><th scope="row">{@code \p{Alpha}}</th>
651 * <td>An alphabetic character:{@code \p{IsAlphabetic}}</td></tr>
652 * <tr><th scope="row">{@code \p{Digit}}</th>
653 * <td>A decimal digit character:{@code \p{IsDigit}}</td></tr>
654 * <tr><th scope="row">{@code \p{Alnum}}</th>
655 * <td>An alphanumeric character:{@code [\p{IsAlphabetic}\p{IsDigit}]}</td></tr>
656 * <tr><th scope="row">{@code \p{Punct}}</th>
657 * <td>A punctuation character:{@code \p{IsPunctuation}}</td></tr>
658 * <tr><th scope="row">{@code \p{Graph}}</th>
659 * <td>A visible character: {@code [^\p{IsWhite_Space}\p{gc=Cc}\p{gc=Cs}\p{gc=Cn}]}</td></tr>
660 * <tr><th scope="row">{@code \p{Print}}</th>
661 * <td>A printable character: {@code [\p{Graph}\p{Blank}&&[^\p{Cntrl}]]}</td></tr>
662 * <tr><th scope="row">{@code \p{Blank}}</th>
663 * <td>A space or a tab: {@code [\p{IsWhite_Space}&&[^\p{gc=Zl}\p{gc=Zp}\x0a\x0b\x0c\x0d\x85]]}</td></tr>
664 * <tr><th scope="row">{@code \p{Cntrl}}</th>
665 * <td>A control character: {@code \p{gc=Cc}}</td></tr>
666 * <tr><th scope="row">{@code \p{XDigit}}</th>
667 * <td>A hexadecimal digit: {@code [\p{gc=Nd}\p{IsHex_Digit}]}</td></tr>
668 * <tr><th scope="row">{@code \p{Space}}</th>
669 * <td>A whitespace character:{@code \p{IsWhite_Space}}</td></tr>
670 * <tr><th scope="row">{@code \d}</th>
671 * <td>A digit: {@code \p{IsDigit}}</td></tr>
672 * <tr><th scope="row">{@code \D}</th>
673 * <td>A non-digit: {@code [^\d]}</td></tr>
674 * <tr><th scope="row">{@code \s}</th>
675 * <td>A whitespace character: {@code \p{IsWhite_Space}}</td></tr>
676 * <tr><th scope="row">{@code \S}</th>
677 * <td>A non-whitespace character: {@code [^\s]}</td></tr>
678 * <tr><th scope="row">{@code \w}</th>
679 * <td>A word character: {@code [\p{Alpha}\p{gc=Mn}\p{gc=Me}\p{gc=Mc}\p{Digit}\p{gc=Pc}\p{IsJoin_Control}]}</td></tr>
680 * <tr><th scope="row">{@code \W}</th>
681 * <td>A non-word character: {@code [^\w]}</td></tr>
682 * </tbody>
683 * </table>
684 * <p>
685 * <a id="jcc">
686 * Categories that behave like the java.lang.Character
687 * boolean is<i>methodname</i> methods (except for the deprecated ones) are
688 * available through the same <code>\p{</code><i>prop</i><code>}</code> syntax where
689 * the specified property has the name <code>java<i>methodname</i></code></a>.
690 *
691 * <h3> Comparison to Perl 5 </h3>
692 *
693 * <p>The {@code Pattern} engine performs traditional NFA-based matching
694 * with ordered alternation as occurs in Perl 5.
695 *
696 * <p> Perl constructs not supported by this class: </p>
697 *
698 * <ul>
699 * <li><p> The backreference constructs, <code>\g{</code><i>n</i><code>}</code> for
700 * the <i>n</i><sup>th</sup><a href="#cg">capturing group</a> and
1185 *
1186 * <p> When there is a positive-width match at the beginning of the input
1187 * sequence then an empty leading substring is included at the beginning
1188 * of the resulting array. A zero-width match at the beginning however
1189 * never produces such empty leading substring.
1190 *
1191 * <p> The {@code limit} parameter controls the number of times the
1192 * pattern is applied and therefore affects the length of the resulting
1193 * array. If the limit <i>n</i> is greater than zero then the pattern
1194 * will be applied at most <i>n</i> - 1 times, the array's
1195 * length will be no greater than <i>n</i>, and the array's last entry
1196 * will contain all input beyond the last matched delimiter. If <i>n</i>
1197 * is non-positive then the pattern will be applied as many times as
1198 * possible and the array can have any length. If <i>n</i> is zero then
1199 * the pattern will be applied as many times as possible, the array can
1200 * have any length, and trailing empty strings will be discarded.
1201 *
1202 * <p> The input {@code "boo:and:foo"}, for example, yields the following
1203 * results with these parameters:
1204 *
1205 * <table class="plain" style="margin-left:2em;">
1206 * <caption style="display:none">Split example showing regex, limit, and result</caption>
1207 * <thead>
1208 * <tr>
1209 * <th scope="col">Regex</th>
1210 * <th scope="col">Limit</th>
1211 * <th scope="col">Result</th>
1212 * </tr>
1213 * </thead>
1214 * <tbody>
1215 * <tr><th scope="row" rowspan="3" style="font-weight:normal">:</th>
1216 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">2</th>
1217 * <td>{@code { "boo", "and:foo" }}</td></tr>
1218 * <tr><!-- : -->
1219 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
1220 * <td>{@code { "boo", "and", "foo" }}</td></tr>
1221 * <tr><!-- : -->
1222 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
1223 * <td>{@code { "boo", "and", "foo" }}</td></tr>
1224 * <tr><th scope="row" rowspan="3" style="font-weight:normal">o</th>
1225 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
1226 * <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
1227 * <tr><!-- o -->
1228 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
1229 * <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
1230 * <tr><!-- o -->
1231 * <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">0</th>
1232 * <td>{@code { "b", "", ":and:f" }}</td></tr>
1233 * </tbody>
1234 * </table>
1235 *
1236 * @param input
1237 * The character sequence to be split
1238 *
1239 * @param limit
1240 * The result threshold, as described above
1241 *
1242 * @return The array of strings computed by splitting the input
1243 * around matches of this pattern
1244 */
1245 public String[] split(CharSequence input, int limit) {
1246 int index = 0;
1247 boolean matchLimited = limit > 0;
1248 ArrayList<String> matchList = new ArrayList<>();
1249 Matcher m = matcher(input);
1250
1251 // Add segments before each match found
1252 while(m.find()) {
1253 if (!matchLimited || matchList.size() < limit - 1) {
1254 if (index == 0 && index == m.start() && m.start() == m.end()) {
1278 // Construct result
1279 int resultSize = matchList.size();
1280 if (limit == 0)
1281 while (resultSize > 0 && matchList.get(resultSize-1).equals(""))
1282 resultSize--;
1283 String[] result = new String[resultSize];
1284 return matchList.subList(0, resultSize).toArray(result);
1285 }
1286
1287 /**
1288 * Splits the given input sequence around matches of this pattern.
1289 *
1290 * <p> This method works as if by invoking the two-argument {@link
1291 * #split(java.lang.CharSequence, int) split} method with the given input
1292 * sequence and a limit argument of zero. Trailing empty strings are
1293 * therefore not included in the resulting array. </p>
1294 *
1295 * <p> The input {@code "boo:and:foo"}, for example, yields the following
1296 * results with these expressions:
1297 *
1298 * <table class="plain" style="margin-left:2em">
1299 * <caption style="display:none">Split examples showing regex and result</caption>
1300 * <thead>
1301 * <tr>
1302 * <th scope="col">Regex</th>
1303 * <th scope="col">Result</th>
1304 * </tr>
1305 * </thead>
1306 * <tbody>
1307 * <tr><th scope="row" style="text-weight:normal">:</th>
1308 * <td>{@code { "boo", "and", "foo" }}</td></tr>
1309 * <tr><th scope="row" style="text-weight:normal">o</th>
1310 * <td>{@code { "b", "", ":and:f" }}</td></tr>
1311 * </tbody>
1312 * </table>
1313 *
1314 *
1315 * @param input
1316 * The character sequence to be split
1317 *
1318 * @return The array of strings computed by splitting the input
1319 * around matches of this pattern
1320 */
1321 public String[] split(CharSequence input) {
1322 return split(input, 0);
1323 }
1324
1325 /**
1326 * Returns a literal pattern {@code String} for the specified
1327 * {@code String}.
1328 *
1329 * <p>This method produces a {@code String} that can be used to
1330 * create a {@code Pattern} that would match the string
1331 * {@code s} as if it were a literal pattern.</p> Metacharacters
1332 * or escape sequences in the input sequence will be given no special
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