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/*
* Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
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*/
package java.util.regex;
import java.text.Normalizer;
import java.util.Locale;
import java.util.Iterator;
import java.util.Map;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Arrays;
import java.util.NoSuchElementException;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Predicate;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* A compiled representation of a regular expression.
*
* <p> A regular expression, specified as a string, must first be compiled into
* an instance of this class. The resulting pattern can then be used to create
* a {@link Matcher} object that can match arbitrary {@linkplain
* java.lang.CharSequence character sequences} against the regular
* expression. All of the state involved in performing a match resides in the
* matcher, so many matchers can share the same pattern.
*
* <p> A typical invocation sequence is thus
*
* <blockquote><pre>
* Pattern p = Pattern.{@link #compile compile}("a*b");
* Matcher m = p.{@link #matcher matcher}("aaaaab");
* boolean b = m.{@link Matcher#matches matches}();</pre></blockquote>
*
* <p> A {@link #matches matches} method is defined by this class as a
* convenience for when a regular expression is used just once. This method
* compiles an expression and matches an input sequence against it in a single
* invocation. The statement
*
* <blockquote><pre>
* boolean b = Pattern.matches("a*b", "aaaaab");</pre></blockquote>
*
* is equivalent to the three statements above, though for repeated matches it
* is less efficient since it does not allow the compiled pattern to be reused.
*
* <p> Instances of this class are immutable and are safe for use by multiple
* concurrent threads. Instances of the {@link Matcher} class are not safe for
* such use.
*
*
* <h3><a name="sum">Summary of regular-expression constructs</a></h3>
*
* <table border="0" cellpadding="1" cellspacing="0"
* summary="Regular expression constructs, and what they match">
*
* <tr align="left">
* <th align="left" id="construct">Construct</th>
* <th align="left" id="matches">Matches</th>
* </tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="characters">Characters</th></tr>
*
* <tr><td valign="top" headers="construct characters"><i>x</i></td>
* <td headers="matches">The character <i>x</i></td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\\</tt></td>
* <td headers="matches">The backslash character</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\0</tt><i>n</i></td>
* <td headers="matches">The character with octal value <tt>0</tt><i>n</i>
* (0 <tt><=</tt> <i>n</i> <tt><=</tt> 7)</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\0</tt><i>nn</i></td>
* <td headers="matches">The character with octal value <tt>0</tt><i>nn</i>
* (0 <tt><=</tt> <i>n</i> <tt><=</tt> 7)</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\0</tt><i>mnn</i></td>
* <td headers="matches">The character with octal value <tt>0</tt><i>mnn</i>
* (0 <tt><=</tt> <i>m</i> <tt><=</tt> 3,
* 0 <tt><=</tt> <i>n</i> <tt><=</tt> 7)</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\x</tt><i>hh</i></td>
* <td headers="matches">The character with hexadecimal value <tt>0x</tt><i>hh</i></td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\u</tt><i>hhhh</i></td>
* <td headers="matches">The character with hexadecimal value <tt>0x</tt><i>hhhh</i></td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\x</tt><i>{h...h}</i></td>
* <td headers="matches">The character with hexadecimal value <tt>0x</tt><i>h...h</i>
* ({@link java.lang.Character#MIN_CODE_POINT Character.MIN_CODE_POINT}
* <= <tt>0x</tt><i>h...h</i> <=
* {@link java.lang.Character#MAX_CODE_POINT Character.MAX_CODE_POINT})</td></tr>
* <tr><td valign="top" headers="matches"><tt>\t</tt></td>
* <td headers="matches">The tab character (<tt>'\u0009'</tt>)</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\n</tt></td>
* <td headers="matches">The newline (line feed) character (<tt>'\u000A'</tt>)</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\r</tt></td>
* <td headers="matches">The carriage-return character (<tt>'\u000D'</tt>)</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\f</tt></td>
* <td headers="matches">The form-feed character (<tt>'\u000C'</tt>)</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\a</tt></td>
* <td headers="matches">The alert (bell) character (<tt>'\u0007'</tt>)</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\e</tt></td>
* <td headers="matches">The escape character (<tt>'\u001B'</tt>)</td></tr>
* <tr><td valign="top" headers="construct characters"><tt>\c</tt><i>x</i></td>
* <td headers="matches">The control character corresponding to <i>x</i></td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="classes">Character classes</th></tr>
*
* <tr><td valign="top" headers="construct classes">{@code [abc]}</td>
* <td headers="matches">{@code a}, {@code b}, or {@code c} (simple class)</td></tr>
* <tr><td valign="top" headers="construct classes">{@code [^abc]}</td>
* <td headers="matches">Any character except {@code a}, {@code b}, or {@code c} (negation)</td></tr>
* <tr><td valign="top" headers="construct classes">{@code [a-zA-Z]}</td>
* <td headers="matches">{@code a} through {@code z}
* or {@code A} through {@code Z}, inclusive (range)</td></tr>
* <tr><td valign="top" headers="construct classes">{@code [a-d[m-p]]}</td>
* <td headers="matches">{@code a} through {@code d},
* or {@code m} through {@code p}: {@code [a-dm-p]} (union)</td></tr>
* <tr><td valign="top" headers="construct classes">{@code [a-z&&[def]]}</td>
* <td headers="matches">{@code d}, {@code e}, or {@code f} (intersection)</tr>
* <tr><td valign="top" headers="construct classes">{@code [a-z&&[^bc]]}</td>
* <td headers="matches">{@code a} through {@code z},
* except for {@code b} and {@code c}: {@code [ad-z]} (subtraction)</td></tr>
* <tr><td valign="top" headers="construct classes">{@code [a-z&&[^m-p]]}</td>
* <td headers="matches">{@code a} through {@code z},
* and not {@code m} through {@code p}: {@code [a-lq-z]}(subtraction)</td></tr>
* <tr><th> </th></tr>
*
* <tr align="left"><th colspan="2" id="predef">Predefined character classes</th></tr>
*
* <tr><td valign="top" headers="construct predef"><tt>.</tt></td>
* <td headers="matches">Any character (may or may not match <a href="#lt">line terminators</a>)</td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\d</tt></td>
* <td headers="matches">A digit: <tt>[0-9]</tt></td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\D</tt></td>
* <td headers="matches">A non-digit: <tt>[^0-9]</tt></td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\h</tt></td>
* <td headers="matches">A horizontal whitespace character:
* <tt>[ \t\xA0\u1680\u180e\u2000-\u200a\u202f\u205f\u3000]</tt></td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\H</tt></td>
* <td headers="matches">A non-horizontal whitespace character: <tt>[^\h]</tt></td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\s</tt></td>
* <td headers="matches">A whitespace character: <tt>[ \t\n\x0B\f\r]</tt></td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\S</tt></td>
* <td headers="matches">A non-whitespace character: <tt>[^\s]</tt></td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\v</tt></td>
* <td headers="matches">A vertical whitespace character: <tt>[\n\x0B\f\r\x85\u2028\u2029]</tt>
* </td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\V</tt></td>
* <td headers="matches">A non-vertical whitespace character: <tt>[^\v]</tt></td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\w</tt></td>
* <td headers="matches">A word character: <tt>[a-zA-Z_0-9]</tt></td></tr>
* <tr><td valign="top" headers="construct predef"><tt>\W</tt></td>
* <td headers="matches">A non-word character: <tt>[^\w]</tt></td></tr>
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="posix"><b>POSIX character classes (US-ASCII only)</b></th></tr>
*
* <tr><td valign="top" headers="construct posix">{@code \p{Lower}}</td>
* <td headers="matches">A lower-case alphabetic character: {@code [a-z]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{Upper}}</td>
* <td headers="matches">An upper-case alphabetic character:{@code [A-Z]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{ASCII}}</td>
* <td headers="matches">All ASCII:{@code [\x00-\x7F]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{Alpha}}</td>
* <td headers="matches">An alphabetic character:{@code [\p{Lower}\p{Upper}]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{Digit}}</td>
* <td headers="matches">A decimal digit: {@code [0-9]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{Alnum}}</td>
* <td headers="matches">An alphanumeric character:{@code [\p{Alpha}\p{Digit}]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{Punct}}</td>
* <td headers="matches">Punctuation: One of {@code !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~}</td></tr>
* <!-- {@code [\!"#\$%&'\(\)\*\+,\-\./:;\<=\>\?@\[\\\]\^_`\{\|\}~]}
* {@code [\X21-\X2F\X31-\X40\X5B-\X60\X7B-\X7E]} -->
* <tr><td valign="top" headers="construct posix">{@code \p{Graph}}</td>
* <td headers="matches">A visible character: {@code [\p{Alnum}\p{Punct}]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{Print}}</td>
* <td headers="matches">A printable character: {@code [\p{Graph}\x20]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{Blank}}</td>
* <td headers="matches">A space or a tab: {@code [ \t]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{Cntrl}}</td>
* <td headers="matches">A control character: {@code [\x00-\x1F\x7F]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{XDigit}}</td>
* <td headers="matches">A hexadecimal digit: {@code [0-9a-fA-F]}</td></tr>
* <tr><td valign="top" headers="construct posix">{@code \p{Space}}</td>
* <td headers="matches">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2">java.lang.Character classes (simple <a href="#jcc">java character type</a>)</th></tr>
*
* <tr><td valign="top"><tt>\p{javaLowerCase}</tt></td>
* <td>Equivalent to java.lang.Character.isLowerCase()</td></tr>
* <tr><td valign="top"><tt>\p{javaUpperCase}</tt></td>
* <td>Equivalent to java.lang.Character.isUpperCase()</td></tr>
* <tr><td valign="top"><tt>\p{javaWhitespace}</tt></td>
* <td>Equivalent to java.lang.Character.isWhitespace()</td></tr>
* <tr><td valign="top"><tt>\p{javaMirrored}</tt></td>
* <td>Equivalent to java.lang.Character.isMirrored()</td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="unicode">Classes for Unicode scripts, blocks, categories and binary properties</th></tr>
* <tr><td valign="top" headers="construct unicode">{@code \p{IsLatin}}</td>
* <td headers="matches">A Latin script character (<a href="#usc">script</a>)</td></tr>
* <tr><td valign="top" headers="construct unicode">{@code \p{InGreek}}</td>
* <td headers="matches">A character in the Greek block (<a href="#ubc">block</a>)</td></tr>
* <tr><td valign="top" headers="construct unicode">{@code \p{Lu}}</td>
* <td headers="matches">An uppercase letter (<a href="#ucc">category</a>)</td></tr>
* <tr><td valign="top" headers="construct unicode">{@code \p{IsAlphabetic}}</td>
* <td headers="matches">An alphabetic character (<a href="#ubpc">binary property</a>)</td></tr>
* <tr><td valign="top" headers="construct unicode">{@code \p{Sc}}</td>
* <td headers="matches">A currency symbol</td></tr>
* <tr><td valign="top" headers="construct unicode">{@code \P{InGreek}}</td>
* <td headers="matches">Any character except one in the Greek block (negation)</td></tr>
* <tr><td valign="top" headers="construct unicode">{@code [\p{L}&&[^\p{Lu}]]}</td>
* <td headers="matches">Any letter except an uppercase letter (subtraction)</td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="bounds">Boundary matchers</th></tr>
*
* <tr><td valign="top" headers="construct bounds"><tt>^</tt></td>
* <td headers="matches">The beginning of a line</td></tr>
* <tr><td valign="top" headers="construct bounds"><tt>$</tt></td>
* <td headers="matches">The end of a line</td></tr>
* <tr><td valign="top" headers="construct bounds"><tt>\b</tt></td>
* <td headers="matches">A word boundary</td></tr>
* <tr><td valign="top" headers="construct bounds"><tt>\B</tt></td>
* <td headers="matches">A non-word boundary</td></tr>
* <tr><td valign="top" headers="construct bounds"><tt>\A</tt></td>
* <td headers="matches">The beginning of the input</td></tr>
* <tr><td valign="top" headers="construct bounds"><tt>\G</tt></td>
* <td headers="matches">The end of the previous match</td></tr>
* <tr><td valign="top" headers="construct bounds"><tt>\Z</tt></td>
* <td headers="matches">The end of the input but for the final
* <a href="#lt">terminator</a>, if any</td></tr>
* <tr><td valign="top" headers="construct bounds"><tt>\z</tt></td>
* <td headers="matches">The end of the input</td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="lineending">Linebreak matcher</th></tr>
* <tr><td valign="top" headers="construct lineending"><tt>\R</tt></td>
* <td headers="matches">Any Unicode linebreak sequence, is equivalent to
* <tt>\u000D\u000A|[\u000A\u000B\u000C\u000D\u0085\u2028\u2029]
* </tt></td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="greedy">Greedy quantifiers</th></tr>
*
* <tr><td valign="top" headers="construct greedy"><i>X</i><tt>?</tt></td>
* <td headers="matches"><i>X</i>, once or not at all</td></tr>
* <tr><td valign="top" headers="construct greedy"><i>X</i><tt>*</tt></td>
* <td headers="matches"><i>X</i>, zero or more times</td></tr>
* <tr><td valign="top" headers="construct greedy"><i>X</i><tt>+</tt></td>
* <td headers="matches"><i>X</i>, one or more times</td></tr>
* <tr><td valign="top" headers="construct greedy"><i>X</i><tt>{</tt><i>n</i><tt>}</tt></td>
* <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
* <tr><td valign="top" headers="construct greedy"><i>X</i><tt>{</tt><i>n</i><tt>,}</tt></td>
* <td headers="matches"><i>X</i>, at least <i>n</i> times</td></tr>
* <tr><td valign="top" headers="construct greedy"><i>X</i><tt>{</tt><i>n</i><tt>,</tt><i>m</i><tt>}</tt></td>
* <td headers="matches"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="reluc">Reluctant quantifiers</th></tr>
*
* <tr><td valign="top" headers="construct reluc"><i>X</i><tt>??</tt></td>
* <td headers="matches"><i>X</i>, once or not at all</td></tr>
* <tr><td valign="top" headers="construct reluc"><i>X</i><tt>*?</tt></td>
* <td headers="matches"><i>X</i>, zero or more times</td></tr>
* <tr><td valign="top" headers="construct reluc"><i>X</i><tt>+?</tt></td>
* <td headers="matches"><i>X</i>, one or more times</td></tr>
* <tr><td valign="top" headers="construct reluc"><i>X</i><tt>{</tt><i>n</i><tt>}?</tt></td>
* <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
* <tr><td valign="top" headers="construct reluc"><i>X</i><tt>{</tt><i>n</i><tt>,}?</tt></td>
* <td headers="matches"><i>X</i>, at least <i>n</i> times</td></tr>
* <tr><td valign="top" headers="construct reluc"><i>X</i><tt>{</tt><i>n</i><tt>,</tt><i>m</i><tt>}?</tt></td>
* <td headers="matches"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="poss">Possessive quantifiers</th></tr>
*
* <tr><td valign="top" headers="construct poss"><i>X</i><tt>?+</tt></td>
* <td headers="matches"><i>X</i>, once or not at all</td></tr>
* <tr><td valign="top" headers="construct poss"><i>X</i><tt>*+</tt></td>
* <td headers="matches"><i>X</i>, zero or more times</td></tr>
* <tr><td valign="top" headers="construct poss"><i>X</i><tt>++</tt></td>
* <td headers="matches"><i>X</i>, one or more times</td></tr>
* <tr><td valign="top" headers="construct poss"><i>X</i><tt>{</tt><i>n</i><tt>}+</tt></td>
* <td headers="matches"><i>X</i>, exactly <i>n</i> times</td></tr>
* <tr><td valign="top" headers="construct poss"><i>X</i><tt>{</tt><i>n</i><tt>,}+</tt></td>
* <td headers="matches"><i>X</i>, at least <i>n</i> times</td></tr>
* <tr><td valign="top" headers="construct poss"><i>X</i><tt>{</tt><i>n</i><tt>,</tt><i>m</i><tt>}+</tt></td>
* <td headers="matches"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="logical">Logical operators</th></tr>
*
* <tr><td valign="top" headers="construct logical"><i>XY</i></td>
* <td headers="matches"><i>X</i> followed by <i>Y</i></td></tr>
* <tr><td valign="top" headers="construct logical"><i>X</i><tt>|</tt><i>Y</i></td>
* <td headers="matches">Either <i>X</i> or <i>Y</i></td></tr>
* <tr><td valign="top" headers="construct logical"><tt>(</tt><i>X</i><tt>)</tt></td>
* <td headers="matches">X, as a <a href="#cg">capturing group</a></td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="backref">Back references</th></tr>
*
* <tr><td valign="bottom" headers="construct backref"><tt>\</tt><i>n</i></td>
* <td valign="bottom" headers="matches">Whatever the <i>n</i><sup>th</sup>
* <a href="#cg">capturing group</a> matched</td></tr>
*
* <tr><td valign="bottom" headers="construct backref"><tt>\</tt><i>k</i><<i>name</i>></td>
* <td valign="bottom" headers="matches">Whatever the
* <a href="#groupname">named-capturing group</a> "name" matched</td></tr>
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="quot">Quotation</th></tr>
*
* <tr><td valign="top" headers="construct quot"><tt>\</tt></td>
* <td headers="matches">Nothing, but quotes the following character</td></tr>
* <tr><td valign="top" headers="construct quot"><tt>\Q</tt></td>
* <td headers="matches">Nothing, but quotes all characters until <tt>\E</tt></td></tr>
* <tr><td valign="top" headers="construct quot"><tt>\E</tt></td>
* <td headers="matches">Nothing, but ends quoting started by <tt>\Q</tt></td></tr>
* <!-- Metachars: !$()*+.<>?[\]^{|} -->
*
* <tr><th> </th></tr>
* <tr align="left"><th colspan="2" id="special">Special constructs (named-capturing and non-capturing)</th></tr>
*
* <tr><td valign="top" headers="construct special"><tt>(?<<a href="#groupname">name</a>></tt><i>X</i><tt>)</tt></td>
* <td headers="matches"><i>X</i>, as a named-capturing group</td></tr>
* <tr><td valign="top" headers="construct special"><tt>(?:</tt><i>X</i><tt>)</tt></td>
* <td headers="matches"><i>X</i>, as a non-capturing group</td></tr>
* <tr><td valign="top" headers="construct special"><tt>(?idmsuxU-idmsuxU) </tt></td>
* <td headers="matches">Nothing, but turns match flags <a href="#CASE_INSENSITIVE">i</a>
* <a href="#UNIX_LINES">d</a> <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a>
* <a href="#UNICODE_CASE">u</a> <a href="#COMMENTS">x</a> <a href="#UNICODE_CHARACTER_CLASS">U</a>
* on - off</td></tr>
* <tr><td valign="top" headers="construct special"><tt>(?idmsux-idmsux:</tt><i>X</i><tt>)</tt> </td>
* <td headers="matches"><i>X</i>, as a <a href="#cg">non-capturing group</a> with the
* given flags <a href="#CASE_INSENSITIVE">i</a> <a href="#UNIX_LINES">d</a>
* <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a> <a href="#UNICODE_CASE">u</a >
* <a href="#COMMENTS">x</a> on - off</td></tr>
* <tr><td valign="top" headers="construct special"><tt>(?=</tt><i>X</i><tt>)</tt></td>
* <td headers="matches"><i>X</i>, via zero-width positive lookahead</td></tr>
* <tr><td valign="top" headers="construct special"><tt>(?!</tt><i>X</i><tt>)</tt></td>
* <td headers="matches"><i>X</i>, via zero-width negative lookahead</td></tr>
* <tr><td valign="top" headers="construct special"><tt>(?<=</tt><i>X</i><tt>)</tt></td>
* <td headers="matches"><i>X</i>, via zero-width positive lookbehind</td></tr>
* <tr><td valign="top" headers="construct special"><tt>(?<!</tt><i>X</i><tt>)</tt></td>
* <td headers="matches"><i>X</i>, via zero-width negative lookbehind</td></tr>
* <tr><td valign="top" headers="construct special"><tt>(?></tt><i>X</i><tt>)</tt></td>
* <td headers="matches"><i>X</i>, as an independent, non-capturing group</td></tr>
*
* </table>
*
* <hr>
*
*
* <h3><a name="bs">Backslashes, escapes, and quoting</a></h3>
*
* <p> The backslash character (<tt>'\'</tt>) serves to introduce escaped
* constructs, as defined in the table above, as well as to quote characters
* that otherwise would be interpreted as unescaped constructs. Thus the
* expression <tt>\\</tt> matches a single backslash and <tt>\{</tt> matches a
* left brace.
*
* <p> It is an error to use a backslash prior to any alphabetic character that
* does not denote an escaped construct; these are reserved for future
* extensions to the regular-expression language. A backslash may be used
* prior to a non-alphabetic character regardless of whether that character is
* part of an unescaped construct.
*
* <p> Backslashes within string literals in Java source code are interpreted
* as required by
* <cite>The Java™ Language Specification</cite>
* as either Unicode escapes (section 3.3) or other character escapes (section 3.10.6)
* It is therefore necessary to double backslashes in string
* literals that represent regular expressions to protect them from
* interpretation by the Java bytecode compiler. The string literal
* <tt>"\b"</tt>, for example, matches a single backspace character when
* interpreted as a regular expression, while <tt>"\\b"</tt> matches a
* word boundary. The string literal <tt>"\(hello\)"</tt> is illegal
* and leads to a compile-time error; in order to match the string
* <tt>(hello)</tt> the string literal <tt>"\\(hello\\)"</tt>
* must be used.
*
* <h3><a name="cc">Character Classes</a></h3>
*
* <p> Character classes may appear within other character classes, and
* may be composed by the union operator (implicit) and the intersection
* operator (<tt>&&</tt>).
* The union operator denotes a class that contains every character that is
* in at least one of its operand classes. The intersection operator
* denotes a class that contains every character that is in both of its
* operand classes.
*
* <p> The precedence of character-class operators is as follows, from
* highest to lowest:
*
* <blockquote><table border="0" cellpadding="1" cellspacing="0"
* summary="Precedence of character class operators.">
* <tr><th>1 </th>
* <td>Literal escape </td>
* <td><tt>\x</tt></td></tr>
* <tr><th>2 </th>
* <td>Grouping</td>
* <td><tt>[...]</tt></td></tr>
* <tr><th>3 </th>
* <td>Range</td>
* <td><tt>a-z</tt></td></tr>
* <tr><th>4 </th>
* <td>Union</td>
* <td><tt>[a-e][i-u]</tt></td></tr>
* <tr><th>5 </th>
* <td>Intersection</td>
* <td>{@code [a-z&&[aeiou]]}</td></tr>
* </table></blockquote>
*
* <p> Note that a different set of metacharacters are in effect inside
* a character class than outside a character class. For instance, the
* regular expression <tt>.</tt> loses its special meaning inside a
* character class, while the expression <tt>-</tt> becomes a range
* forming metacharacter.
*
* <h3><a name="lt">Line terminators</a></h3>
*
* <p> A <i>line terminator</i> is a one- or two-character sequence that marks
* the end of a line of the input character sequence. The following are
* recognized as line terminators:
*
* <ul>
*
* <li> A newline (line feed) character (<tt>'\n'</tt>),
*
* <li> A carriage-return character followed immediately by a newline
* character (<tt>"\r\n"</tt>),
*
* <li> A standalone carriage-return character (<tt>'\r'</tt>),
*
* <li> A next-line character (<tt>'\u0085'</tt>),
*
* <li> A line-separator character (<tt>'\u2028'</tt>), or
*
* <li> A paragraph-separator character (<tt>'\u2029</tt>).
*
* </ul>
* <p>If {@link #UNIX_LINES} mode is activated, then the only line terminators
* recognized are newline characters.
*
* <p> The regular expression <tt>.</tt> matches any character except a line
* terminator unless the {@link #DOTALL} flag is specified.
*
* <p> By default, the regular expressions <tt>^</tt> and <tt>$</tt> ignore
* line terminators and only match at the beginning and the end, respectively,
* of the entire input sequence. If {@link #MULTILINE} mode is activated then
* <tt>^</tt> matches at the beginning of input and after any line terminator
* except at the end of input. When in {@link #MULTILINE} mode <tt>$</tt>
* matches just before a line terminator or the end of the input sequence.
*
* <h3><a name="cg">Groups and capturing</a></h3>
*
* <h4><a name="gnumber">Group number</a></h4>
* <p> Capturing groups are numbered by counting their opening parentheses from
* left to right. In the expression <tt>((A)(B(C)))</tt>, for example, there
* are four such groups: </p>
*
* <blockquote><table cellpadding=1 cellspacing=0 summary="Capturing group numberings">
* <tr><th>1 </th>
* <td><tt>((A)(B(C)))</tt></td></tr>
* <tr><th>2 </th>
* <td><tt>(A)</tt></td></tr>
* <tr><th>3 </th>
* <td><tt>(B(C))</tt></td></tr>
* <tr><th>4 </th>
* <td><tt>(C)</tt></td></tr>
* </table></blockquote>
*
* <p> Group zero always stands for the entire expression.
*
* <p> Capturing groups are so named because, during a match, each subsequence
* of the input sequence that matches such a group is saved. The captured
* subsequence may be used later in the expression, via a back reference, and
* may also be retrieved from the matcher once the match operation is complete.
*
* <h4><a name="groupname">Group name</a></h4>
* <p>A capturing group can also be assigned a "name", a <tt>named-capturing group</tt>,
* and then be back-referenced later by the "name". Group names are composed of
* the following characters. The first character must be a <tt>letter</tt>.
*
* <ul>
* <li> The uppercase letters <tt>'A'</tt> through <tt>'Z'</tt>
* (<tt>'\u0041'</tt> through <tt>'\u005a'</tt>),
* <li> The lowercase letters <tt>'a'</tt> through <tt>'z'</tt>
* (<tt>'\u0061'</tt> through <tt>'\u007a'</tt>),
* <li> The digits <tt>'0'</tt> through <tt>'9'</tt>
* (<tt>'\u0030'</tt> through <tt>'\u0039'</tt>),
* </ul>
*
* <p> A <tt>named-capturing group</tt> is still numbered as described in
* <a href="#gnumber">Group number</a>.
*
* <p> The captured input associated with a group is always the subsequence
* that the group most recently matched. If a group is evaluated a second time
* because of quantification then its previously-captured value, if any, will
* be retained if the second evaluation fails. Matching the string
* <tt>"aba"</tt> against the expression <tt>(a(b)?)+</tt>, for example, leaves
* group two set to <tt>"b"</tt>. All captured input is discarded at the
* beginning of each match.
*
* <p> Groups beginning with <tt>(?</tt> are either pure, <i>non-capturing</i> groups
* that do not capture text and do not count towards the group total, or
* <i>named-capturing</i> group.
*
* <h3> Unicode support </h3>
*
* <p> This class is in conformance with Level 1 of <a
* href="http://www.unicode.org/reports/tr18/"><i>Unicode Technical
* Standard #18: Unicode Regular Expression</i></a>, plus RL2.1
* Canonical Equivalents.
* <p>
* <b>Unicode escape sequences</b> such as <tt>\u2014</tt> in Java source code
* are processed as described in section 3.3 of
* <cite>The Java™ Language Specification</cite>.
* Such escape sequences are also implemented directly by the regular-expression
* parser so that Unicode escapes can be used in expressions that are read from
* files or from the keyboard. Thus the strings <tt>"\u2014"</tt> and
* <tt>"\\u2014"</tt>, while not equal, compile into the same pattern, which
* matches the character with hexadecimal value <tt>0x2014</tt>.
* <p>
* A Unicode character can also be represented in a regular-expression by
* using its <b>Hex notation</b>(hexadecimal code point value) directly as described in construct
* <tt>\x{...}</tt>, for example a supplementary character U+2011F
* can be specified as <tt>\x{2011F}</tt>, instead of two consecutive
* Unicode escape sequences of the surrogate pair
* <tt>\uD840</tt><tt>\uDD1F</tt>.
* <p>
* Unicode scripts, blocks, categories and binary properties are written with
* the <tt>\p</tt> and <tt>\P</tt> constructs as in Perl.
* <tt>\p{</tt><i>prop</i><tt>}</tt> matches if
* the input has the property <i>prop</i>, while <tt>\P{</tt><i>prop</i><tt>}</tt>
* does not match if the input has that property.
* <p>
* Scripts, blocks, categories and binary properties can be used both inside
* and outside of a character class.
*
* <p>
* <b><a name="usc">Scripts</a></b> are specified either with the prefix {@code Is}, as in
* {@code IsHiragana}, or by using the {@code script} keyword (or its short
* form {@code sc})as in {@code script=Hiragana} or {@code sc=Hiragana}.
* <p>
* The script names supported by <code>Pattern</code> are the valid script names
* accepted and defined by
* {@link java.lang.Character.UnicodeScript#forName(String) UnicodeScript.forName}.
*
* <p>
* <b><a name="ubc">Blocks</a></b> are specified with the prefix {@code In}, as in
* {@code InMongolian}, or by using the keyword {@code block} (or its short
* form {@code blk}) as in {@code block=Mongolian} or {@code blk=Mongolian}.
* <p>
* The block names supported by <code>Pattern</code> are the valid block names
* accepted and defined by
* {@link java.lang.Character.UnicodeBlock#forName(String) UnicodeBlock.forName}.
* <p>
*
* <b><a name="ucc">Categories</a></b> may be specified with the optional prefix {@code Is}:
* Both {@code \p{L}} and {@code \p{IsL}} denote the category of Unicode
* letters. Same as scripts and blocks, categories can also be specified
* by using the keyword {@code general_category} (or its short form
* {@code gc}) as in {@code general_category=Lu} or {@code gc=Lu}.
* <p>
* The supported categories are those of
* <a href="http://www.unicode.org/unicode/standard/standard.html">
* <i>The Unicode Standard</i></a> in the version specified by the
* {@link java.lang.Character Character} class. The category names are those
* defined in the Standard, both normative and informative.
* <p>
*
* <b><a name="ubpc">Binary properties</a></b> are specified with the prefix {@code Is}, as in
* {@code IsAlphabetic}. The supported binary properties by <code>Pattern</code>
* are
* <ul>
* <li> Alphabetic
* <li> Ideographic
* <li> Letter
* <li> Lowercase
* <li> Uppercase
* <li> Titlecase
* <li> Punctuation
* <Li> Control
* <li> White_Space
* <li> Digit
* <li> Hex_Digit
* <li> Join_Control
* <li> Noncharacter_Code_Point
* <li> Assigned
* </ul>
* <p>
* The following <b>Predefined Character classes</b> and <b>POSIX character classes</b>
* are in conformance with the recommendation of <i>Annex C: Compatibility Properties</i>
* of <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Regular Expression
* </i></a>, when {@link #UNICODE_CHARACTER_CLASS} flag is specified.
*
* <table border="0" cellpadding="1" cellspacing="0"
* summary="predefined and posix character classes in Unicode mode">
* <tr align="left">
* <th align="left" id="predef_classes">Classes</th>
* <th align="left" id="predef_matches">Matches</th>
*</tr>
* <tr><td><tt>\p{Lower}</tt></td>
* <td>A lowercase character:<tt>\p{IsLowercase}</tt></td></tr>
* <tr><td><tt>\p{Upper}</tt></td>
* <td>An uppercase character:<tt>\p{IsUppercase}</tt></td></tr>
* <tr><td><tt>\p{ASCII}</tt></td>
* <td>All ASCII:<tt>[\x00-\x7F]</tt></td></tr>
* <tr><td><tt>\p{Alpha}</tt></td>
* <td>An alphabetic character:<tt>\p{IsAlphabetic}</tt></td></tr>
* <tr><td><tt>\p{Digit}</tt></td>
* <td>A decimal digit character:<tt>p{IsDigit}</tt></td></tr>
* <tr><td><tt>\p{Alnum}</tt></td>
* <td>An alphanumeric character:<tt>[\p{IsAlphabetic}\p{IsDigit}]</tt></td></tr>
* <tr><td><tt>\p{Punct}</tt></td>
* <td>A punctuation character:<tt>p{IsPunctuation}</tt></td></tr>
* <tr><td><tt>\p{Graph}</tt></td>
* <td>A visible character: <tt>[^\p{IsWhite_Space}\p{gc=Cc}\p{gc=Cs}\p{gc=Cn}]</tt></td></tr>
* <tr><td><tt>\p{Print}</tt></td>
* <td>A printable character: {@code [\p{Graph}\p{Blank}&&[^\p{Cntrl}]]}</td></tr>
* <tr><td><tt>\p{Blank}</tt></td>
* <td>A space or a tab: {@code [\p{IsWhite_Space}&&[^\p{gc=Zl}\p{gc=Zp}\x0a\x0b\x0c\x0d\x85]]}</td></tr>
* <tr><td><tt>\p{Cntrl}</tt></td>
* <td>A control character: <tt>\p{gc=Cc}</tt></td></tr>
* <tr><td><tt>\p{XDigit}</tt></td>
* <td>A hexadecimal digit: <tt>[\p{gc=Nd}\p{IsHex_Digit}]</tt></td></tr>
* <tr><td><tt>\p{Space}</tt></td>
* <td>A whitespace character:<tt>\p{IsWhite_Space}</tt></td></tr>
* <tr><td><tt>\d</tt></td>
* <td>A digit: <tt>\p{IsDigit}</tt></td></tr>
* <tr><td><tt>\D</tt></td>
* <td>A non-digit: <tt>[^\d]</tt></td></tr>
* <tr><td><tt>\s</tt></td>
* <td>A whitespace character: <tt>\p{IsWhite_Space}</tt></td></tr>
* <tr><td><tt>\S</tt></td>
* <td>A non-whitespace character: <tt>[^\s]</tt></td></tr>
* <tr><td><tt>\w</tt></td>
* <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>
* <tr><td><tt>\W</tt></td>
* <td>A non-word character: <tt>[^\w]</tt></td></tr>
* </table>
* <p>
* <a name="jcc">
* Categories that behave like the java.lang.Character
* boolean is<i>methodname</i> methods (except for the deprecated ones) are
* available through the same <tt>\p{</tt><i>prop</i><tt>}</tt> syntax where
* the specified property has the name <tt>java<i>methodname</i></tt></a>.
*
* <h3> Comparison to Perl 5 </h3>
*
* <p>The <code>Pattern</code> engine performs traditional NFA-based matching
* with ordered alternation as occurs in Perl 5.
*
* <p> Perl constructs not supported by this class: </p>
*
* <ul>
* <li><p> Predefined character classes (Unicode character)
* <p><tt>\X </tt>Match Unicode
* <a href="http://www.unicode.org/reports/tr18/#Default_Grapheme_Clusters">
* <i>extended grapheme cluster</i></a>
* </p></li>
*
* <li><p> The backreference constructs, <tt>\g{</tt><i>n</i><tt>}</tt> for
* the <i>n</i><sup>th</sup><a href="#cg">capturing group</a> and
* <tt>\g{</tt><i>name</i><tt>}</tt> for
* <a href="#groupname">named-capturing group</a>.
* </p></li>
*
* <li><p> The named character construct, <tt>\N{</tt><i>name</i><tt>}</tt>
* for a Unicode character by its name.
* </p></li>
*
* <li><p> The conditional constructs
* <tt>(?(</tt><i>condition</i><tt>)</tt><i>X</i><tt>)</tt> and
* <tt>(?(</tt><i>condition</i><tt>)</tt><i>X</i><tt>|</tt><i>Y</i><tt>)</tt>,
* </p></li>
*
* <li><p> The embedded code constructs <tt>(?{</tt><i>code</i><tt>})</tt>
* and <tt>(??{</tt><i>code</i><tt>})</tt>,</p></li>
*
* <li><p> The embedded comment syntax <tt>(?#comment)</tt>, and </p></li>
*
* <li><p> The preprocessing operations <tt>\l</tt> <tt>\u</tt>,
* <tt>\L</tt>, and <tt>\U</tt>. </p></li>
*
* </ul>
*
* <p> Constructs supported by this class but not by Perl: </p>
*
* <ul>
*
* <li><p> Character-class union and intersection as described
* <a href="#cc">above</a>.</p></li>
*
* </ul>
*
* <p> Notable differences from Perl: </p>
*
* <ul>
*
* <li><p> In Perl, <tt>\1</tt> through <tt>\9</tt> are always interpreted
* as back references; a backslash-escaped number greater than <tt>9</tt> is
* treated as a back reference if at least that many subexpressions exist,
* otherwise it is interpreted, if possible, as an octal escape. In this
* class octal escapes must always begin with a zero. In this class,
* <tt>\1</tt> through <tt>\9</tt> are always interpreted as back
* references, and a larger number is accepted as a back reference if at
* least that many subexpressions exist at that point in the regular
* expression, otherwise the parser will drop digits until the number is
* smaller or equal to the existing number of groups or it is one digit.
* </p></li>
*
* <li><p> Perl uses the <tt>g</tt> flag to request a match that resumes
* where the last match left off. This functionality is provided implicitly
* by the {@link Matcher} class: Repeated invocations of the {@link
* Matcher#find find} method will resume where the last match left off,
* unless the matcher is reset. </p></li>
*
* <li><p> In Perl, embedded flags at the top level of an expression affect
* the whole expression. In this class, embedded flags always take effect
* at the point at which they appear, whether they are at the top level or
* within a group; in the latter case, flags are restored at the end of the
* group just as in Perl. </p></li>
*
* </ul>
*
*
* <p> For a more precise description of the behavior of regular expression
* constructs, please see <a href="http://www.oreilly.com/catalog/regex3/">
* <i>Mastering Regular Expressions, 3nd Edition</i>, Jeffrey E. F. Friedl,
* O'Reilly and Associates, 2006.</a>
* </p>
*
* @see java.lang.String#split(String, int)
* @see java.lang.String#split(String)
*
* @author Mike McCloskey
* @author Mark Reinhold
* @author JSR-51 Expert Group
* @since 1.4
* @spec JSR-51
*/
public final class Pattern
implements java.io.Serializable
{
/**
* Regular expression modifier values. Instead of being passed as
* arguments, they can also be passed as inline modifiers.
* For example, the following statements have the same effect.
* <pre>
* RegExp r1 = RegExp.compile("abc", Pattern.I|Pattern.M);
* RegExp r2 = RegExp.compile("(?im)abc", 0);
* </pre>
*
* The flags are duplicated so that the familiar Perl match flag
* names are available.
*/
/**
* Enables Unix lines mode.
*
* <p> In this mode, only the <tt>'\n'</tt> line terminator is recognized
* in the behavior of <tt>.</tt>, <tt>^</tt>, and <tt>$</tt>.
*
* <p> Unix lines mode can also be enabled via the embedded flag
* expression <tt>(?d)</tt>.
*/
public static final int UNIX_LINES = 0x01;
/**
* Enables case-insensitive matching.
*
* <p> By default, case-insensitive matching assumes that only characters
* in the US-ASCII charset are being matched. Unicode-aware
* case-insensitive matching can be enabled by specifying the {@link
* #UNICODE_CASE} flag in conjunction with this flag.
*
* <p> Case-insensitive matching can also be enabled via the embedded flag
* expression <tt>(?i)</tt>.
*
* <p> Specifying this flag may impose a slight performance penalty. </p>
*/
public static final int CASE_INSENSITIVE = 0x02;
/**
* Permits whitespace and comments in pattern.
*
* <p> In this mode, whitespace is ignored, and embedded comments starting
* with <tt>#</tt> are ignored until the end of a line.
*
* <p> Comments mode can also be enabled via the embedded flag
* expression <tt>(?x)</tt>.
*/
public static final int COMMENTS = 0x04;
/**
* Enables multiline mode.
*
* <p> In multiline mode the expressions <tt>^</tt> and <tt>$</tt> match
* just after or just before, respectively, a line terminator or the end of
* the input sequence. By default these expressions only match at the
* beginning and the end of the entire input sequence.
*
* <p> Multiline mode can also be enabled via the embedded flag
* expression <tt>(?m)</tt>. </p>
*/
public static final int MULTILINE = 0x08;
/**
* Enables literal parsing of the pattern.
*
* <p> When this flag is specified then the input string that specifies
* the pattern is treated as a sequence of literal characters.
* Metacharacters or escape sequences in the input sequence will be
* given no special meaning.
*
* <p>The flags CASE_INSENSITIVE and UNICODE_CASE retain their impact on
* matching when used in conjunction with this flag. The other flags
* become superfluous.
*
* <p> There is no embedded flag character for enabling literal parsing.
* @since 1.5
*/
public static final int LITERAL = 0x10;
/**
* Enables dotall mode.
*
* <p> In dotall mode, the expression <tt>.</tt> matches any character,
* including a line terminator. By default this expression does not match
* line terminators.
*
* <p> Dotall mode can also be enabled via the embedded flag
* expression <tt>(?s)</tt>. (The <tt>s</tt> is a mnemonic for
* "single-line" mode, which is what this is called in Perl.) </p>
*/
public static final int DOTALL = 0x20;
/**
* Enables Unicode-aware case folding.
*
* <p> When this flag is specified then case-insensitive matching, when
* enabled by the {@link #CASE_INSENSITIVE} flag, is done in a manner
* consistent with the Unicode Standard. By default, case-insensitive
* matching assumes that only characters in the US-ASCII charset are being
* matched.
*
* <p> Unicode-aware case folding can also be enabled via the embedded flag
* expression <tt>(?u)</tt>.
*
* <p> Specifying this flag may impose a performance penalty. </p>
*/
public static final int UNICODE_CASE = 0x40;
/**
* Enables canonical equivalence.
*
* <p> When this flag is specified then two characters will be considered
* to match if, and only if, their full canonical decompositions match.
* The expression <tt>"a\u030A"</tt>, for example, will match the
* string <tt>"\u00E5"</tt> when this flag is specified. By default,
* matching does not take canonical equivalence into account.
*
* <p> There is no embedded flag character for enabling canonical
* equivalence.
*
* <p> Specifying this flag may impose a performance penalty. </p>
*/
public static final int CANON_EQ = 0x80;
/**
* Enables the Unicode version of <i>Predefined character classes</i> and
* <i>POSIX character classes</i>.
*
* <p> When this flag is specified then the (US-ASCII only)
* <i>Predefined character classes</i> and <i>POSIX character classes</i>
* are in conformance with
* <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Technical
* Standard #18: Unicode Regular Expression</i></a>
* <i>Annex C: Compatibility Properties</i>.
* <p>
* The UNICODE_CHARACTER_CLASS mode can also be enabled via the embedded
* flag expression <tt>(?U)</tt>.
* <p>
* The flag implies UNICODE_CASE, that is, it enables Unicode-aware case
* folding.
* <p>
* Specifying this flag may impose a performance penalty. </p>
* @since 1.7
*/
public static final int UNICODE_CHARACTER_CLASS = 0x100;
/* Pattern has only two serialized components: The pattern string
* and the flags, which are all that is needed to recompile the pattern
* when it is deserialized.
*/
/** use serialVersionUID from Merlin b59 for interoperability */
private static final long serialVersionUID = 5073258162644648461L;
/**
* The original regular-expression pattern string.
*
* @serial
*/
private String pattern;
/**
* The original pattern flags.
*
* @serial
*/
private int flags;
/**
* Boolean indicating this Pattern is compiled; this is necessary in order
* to lazily compile deserialized Patterns.
*/
private transient volatile boolean compiled = false;
/**
* The normalized pattern string.
*/
private transient String normalizedPattern;
/**
* The starting point of state machine for the find operation. This allows
* a match to start anywhere in the input.
*/
transient Node root;
/**
* The root of object tree for a match operation. The pattern is matched
* at the beginning. This may include a find that uses BnM or a First
* node.
*/
transient Node matchRoot;
/**
* Temporary storage used by parsing pattern slice.
*/
transient int[] buffer;
/**
* Map the "name" of the "named capturing group" to its group id
* node.
*/
transient volatile Map<String, Integer> namedGroups;
/**
* Temporary storage used while parsing group references.
*/
transient GroupHead[] groupNodes;
/**
* Temporary null terminated code point array used by pattern compiling.
*/
private transient int[] temp;
/**
* The number of capturing groups in this Pattern. Used by matchers to
* allocate storage needed to perform a match.
*/
transient int capturingGroupCount;
/**
* The local variable count used by parsing tree. Used by matchers to
* allocate storage needed to perform a match.
*/
transient int localCount;
/**
* Index into the pattern string that keeps track of how much has been