# Pattern

public final class **Pattern** extends [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html)  
implements [Serializable](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/Serializable.html) A compiled representation of a regular expression.

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 `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Matcher.html` 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.

A typical invocation sequence is thus

>      Pattern p = Pattern.https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#compile(java.lang.String)("a*b");
>      Matcher m = p.https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#matcher(java.lang.CharSequence)("aaaaab");
>      boolean b = m.https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Matcher.html#matches()();

A `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#matches(java.lang.String,%20java.lang.CharSequence)` 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

> ```
>  boolean b = Pattern.matches("a*b", "aaaaab");
> ```
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.

Instances of this class are immutable and are safe for use by multiple
concurrent threads. Instances of the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Matcher.html` class are not safe for
such use.


### Summary of regular-expression constructs

| Construct | Matches |
|   |
| Characters ||
|:---|:---|
| *x* | The character *x* |
| \\\\ | The backslash character |
| \\0*n* | The character with octal value 0*n* (0 \<= *n* \<= 7) |
| \\0*nn* | The character with octal value 0*nn* (0 \<= *n* \<= 7) |
| \\0*mnn* | The character with octal value 0*mnn* (0 \<= *m* \<= 3, 0 \<= *n* \<= 7) |
| \\x*hh* | The character with hexadecimal value 0x*hh* |
| \\u*hhhh* | The character with hexadecimal value 0x*hhhh* |
| \\x*{h...h}* | The character with hexadecimal value 0x*h...h* (`https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Character.html#MIN_CODE_POINT` \<= 0x*h...h* \<= `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Character.html#MAX_CODE_POINT`) |
| \\t | The tab character ('\\u0009') |
| \\n | The newline (line feed) character ('\\u000A') |
| \\r | The carriage-return character ('\\u000D') |
| \\f | The form-feed character ('\\u000C') |
| \\a | The alert (bell) character ('\\u0007') |
| \\e | The escape character ('\\u001B') |
| \\c*x* | The control character corresponding to *x* |
| `[abc]` | `a`, `b`, or `c` (simple class) |
| `[^abc]` | Any character except `a`, `b`, or `c` (negation) |
| `[a-zA-Z]` | `a` through `z` or `A` through `Z`, inclusive (range) |
| `[a-d[m-p]]` | `a` through `d`, or `m` through `p`: `[a-dm-p]` (union) |
| `[a-z&&[def]]` | `d`, `e`, or `f` (intersection) |
| `[a-z&&[^bc]]` | `a` through `z`, except for `b` and `c`: `[ad-z]` (subtraction) |
| `[a-z&&[^m-p]]` | `a` through `z`, and not `m` through `p`: `[a-lq-z]`(subtraction) |
| . | Any character (may or may not match [line terminators](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#lt)) |
| \\d | A digit: \[0-9\] |
| \\D | A non-digit: \[\^0-9\] |
| \\h | A horizontal whitespace character: \[ \\t\\xA0\\u1680\\u180e\\u2000-\\u200a\\u202f\\u205f\\u3000\] |
| \\H | A non-horizontal whitespace character: \[\^\\h\] |
| \\s | A whitespace character: \[ \\t\\n\\x0B\\f\\r\] |
| \\S | A non-whitespace character: \[\^\\s\] |
| \\v | A vertical whitespace character: \[\\n\\x0B\\f\\r\\x85\\u2028\\u2029\] |
| \\V | A non-vertical whitespace character: \[\^\\v\] |
| \\w | A word character: \[a-zA-Z_0-9\] |
| \\W | A non-word character: \[\^\\w\] |
| `\p{Lower}` | A lower-case alphabetic character: `[a-z]` |
| `\p{Upper}` | An upper-case alphabetic character:`[A-Z]` |
| `\p{ASCII}` | All ASCII:`[\x00-\x7F]` |
| `\p{Alpha}` | An alphabetic character:`[\p{Lower}\p{Upper}]` |
| `\p{Digit}` | A decimal digit: `[0-9]` |
| `\p{Alnum}` | An alphanumeric character:`[\p{Alpha}\p{Digit}]` |
| `\p{Punct}` | Punctuation: One of ``!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~`` |
| `\p{Graph}` | A visible character: `[\p{Alnum}\p{Punct}]` |
| `\p{Print}` | A printable character: `[\p{Graph}\x20]` |
| `\p{Blank}` | A space or a tab: `[ \t]` |
| `\p{Cntrl}` | A control character: `[\x00-\x1F\x7F]` |
| `\p{XDigit}` | A hexadecimal digit: `[0-9a-fA-F]` |
| `\p{Space}` | A whitespace character: `[ \t\n\x0B\f\r]` |
| \\p{javaLowerCase} | Equivalent to java.lang.Character.isLowerCase() |
| \\p{javaUpperCase} | Equivalent to java.lang.Character.isUpperCase() |
| \\p{javaWhitespace} | Equivalent to java.lang.Character.isWhitespace() |
| \\p{javaMirrored} | Equivalent to java.lang.Character.isMirrored() |
| `\p{IsLatin}` | A Latin script character ([script](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#usc)) |
| `\p{InGreek}` | A character in the Greek block ([block](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#ubc)) |
| `\p{Lu}` | An uppercase letter ([category](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#ucc)) |
| `\p{IsAlphabetic}` | An alphabetic character ([binary property](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#ubpc)) |
| `\p{Sc}` | A currency symbol |
| `\P{InGreek}` | Any character except one in the Greek block (negation) |
| `[\p{L}&&[^\p{Lu}]]` | Any letter except an uppercase letter (subtraction) |
| \^ | The beginning of a line |
| $ | The end of a line |
| \\b | A word boundary |
| \\B | A non-word boundary |
| \\A | The beginning of the input |
| \\G | The end of the previous match |
| \\Z | The end of the input but for the final [terminator](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#lt), if any |
| \\z | The end of the input |
| \\R | Any Unicode linebreak sequence, is equivalent to \\u000D\\u000A\|\[\\u000A\\u000B\\u000C\\u000D\\u0085\\u2028\\u2029\] |
| *X*? | *X*, once or not at all |
| *X*\* | *X*, zero or more times |
| *X*+ | *X*, one or more times |
| *X*{*n*} | *X*, exactly *n* times |
| *X*{*n*,} | *X*, at least *n* times |
| *X*{*n*,*m*} | *X*, at least *n* but not more than *m* times |
| *X*?? | *X*, once or not at all |
| *X*\*? | *X*, zero or more times |
| *X*+? | *X*, one or more times |
| *X*{*n*}? | *X*, exactly *n* times |
| *X*{*n*,}? | *X*, at least *n* times |
| *X*{*n*,*m*}? | *X*, at least *n* but not more than *m* times |
| *X*?+ | *X*, once or not at all |
| *X*\*+ | *X*, zero or more times |
| *X*++ | *X*, one or more times |
| *X*{*n*}+ | *X*, exactly *n* times |
| *X*{*n*,}+ | *X*, at least *n* times |
| *X*{*n*,*m*}+ | *X*, at least *n* but not more than *m* times |
| *XY* | *X* followed by *Y* |
| *X*\|*Y* | Either *X* or *Y* |
| (*X*) | X, as a [capturing group](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#cg) |
| \\*n* | Whatever the *n*^th^ [capturing group](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#cg) matched |
| \\*k*\<*name*\> | Whatever the [named-capturing group](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#groupname) "name" matched. Only available for API 26 or above |
| \\ | Nothing, but quotes the following character |
| \\Q | Nothing, but quotes all characters until \\E |
| \\E | Nothing, but ends quoting started by \\Q |
| (?\<[name](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#groupname)\>*X*) | *X*, as a named-capturing group. Only available for API 26 or above. |
| (?:*X*) | *X*, as a non-capturing group |
| (?idmsuxU-idmsuxU) | Nothing, but turns match flags [i](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#CASE_INSENSITIVE) [d](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#UNIX_LINES) [m](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#MULTILINE) [s](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#DOTALL) [u](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#UNICODE_CASE) [x](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#COMMENTS) [U](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#UNICODE_CHARACTER_CLASS) on - off |
| (?idmsux-idmsux:*X*) | *X*, as a [non-capturing group](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#cg) with the given flags [i](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#CASE_INSENSITIVE) [d](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#UNIX_LINES) [m](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#MULTILINE) [s](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#DOTALL) [u](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#UNICODE_CASE) [x](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#COMMENTS) on - off |
| (?=*X*) | *X*, via zero-width positive lookahead |
| (?!*X*) | *X*, via zero-width negative lookahead |
| (?\<=*X*) | *X*, via zero-width positive lookbehind |
| (?\<!*X*) | *X*, via zero-width negative lookbehind |
| (?\>*X*) | *X*, as an independent, non-capturing group |

*** ** * ** ***

### Backslashes, escapes, and quoting

The backslash character ('\\') 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 \\\\ matches a single backslash and \\{ matches a
left brace.

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.

Backslashes within string literals in Java source code are interpreted
as required by
The Java™ Language Specification
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
"\\b", for example, matches a single backspace character when
interpreted as a regular expression, while "\\\\b" matches a
word boundary. The string literal "\\(hello\\)" is illegal
and leads to a compile-time error; in order to match the string
(hello) the string literal "\\\\(hello\\\\)"
must be used.

### Character Classes

Character classes may appear within other character classes, and
may be composed by the union operator (implicit) and the intersection
operator (\&\&).
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.

The precedence of character-class operators is as follows, from
highest to lowest:

> | 1 | Literal escape | \\x |
> | 2 | Grouping | \[...\] |
> | 3 | Range | a-z |
> | 4 | Union | \[a-e\]\[i-u\] |
> | 5 | Intersection | `[a-z&&[aeiou]]` |
> |---|---|---|

Note that a different set of metacharacters are in effect inside
a character class than outside a character class. For instance, the
regular expression . loses its special meaning inside a
character class, while the expression - becomes a range
forming metacharacter.

### Line terminators

A *line terminator* 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:

- A newline (line feed) character ('\\n'),
- A carriage-return character followed immediately by a newline character ("\\r\\n"),
- A standalone carriage-return character ('\\r'),
- A next-line character ('\\u0085'),
- A line-separator character ('\\u2028'), or
- A paragraph-separator character ('\\u2029).

If `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#UNIX_LINES` mode is activated, then the only line terminators
recognized are newline characters.

The regular expression . matches any character except a line
terminator unless the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#DOTALL` flag is specified.

By default, the regular expressions \^ and $ ignore
line terminators and only match at the beginning and the end, respectively,
of the entire input sequence. If `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#MULTILINE` mode is activated then
\^ matches at the beginning of input and after any line terminator
except at the end of input. When in `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#MULTILINE` mode $
matches just before a line terminator or the end of the input sequence.

### Groups and capturing

#### Group number

Capturing groups are numbered by counting their opening parentheses from
left to right. In the expression ((A)(B(C))), for example, there
are four such groups:
>
> | 1 | ((A)(B(C))) |
> | 2 | (A) |
> | 3 | (B(C)) |
> | 4 | (C) |
> |---|---|

Group zero always stands for the entire expression.

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.

#### Group name

The constructs and APIs are available since API level 26. A capturing group
can also be assigned a "name", a named-capturing group,
and then be back-referenced later by the "name". Group names are composed of
the following characters. The first character must be a letter.

- The uppercase letters 'A' through 'Z' ('\\u0041' through '\\u005a'),
- The lowercase letters 'a' through 'z' ('\\u0061' through '\\u007a'),
- The digits '0' through '9' ('\\u0030' through '\\u0039'),

A named-capturing group is still numbered as described in
[Group number](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#gnumber).

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
"aba" against the expression (a(b)?)+, for example, leaves
group two set to "b". All captured input is discarded at the
beginning of each match.

Groups beginning with (? are either pure, *non-capturing* groups
that do not capture text and do not count towards the group total, or
*named-capturing* group.

### Unicode support

This class is in conformance with Level 1 of [*Unicode Technical Standard #18: Unicode Regular Expression*](http://www.unicode.org/reports/tr18/), plus RL2.1
Canonical Equivalents.


**Unicode escape sequences** such as \\u2014 in Java source code
are processed as described in section 3.3 of
The Java™ Language Specification.
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 "\\u2014" and
"\\\\u2014", while not equal, compile into the same pattern, which
matches the character with hexadecimal value 0x2014.


A Unicode character can also be represented in a regular-expression by
using its **Hex notation** (hexadecimal code point value) directly as described in construct
\\x{...}, for example a supplementary character U+2011F
can be specified as \\x{2011F}, instead of two consecutive
Unicode escape sequences of the surrogate pair
\\uD840\\uDD1F.


Unicode scripts, blocks, categories and binary properties are written with
the \\p and \\P constructs as in Perl.
\\p{*prop*} matches if
the input has the property *prop*, while \\P{*prop*}
does not match if the input has that property.


Scripts, blocks, categories and binary properties can be used both inside
and outside of a character class.


**Scripts** are specified either with the prefix `Is`, as in
`IsHiragana`, or by using the `script` keyword (or its short
form `sc`)as in `script=Hiragana` or `sc=Hiragana`.


The script names supported by `Pattern` are the valid script names
accepted and defined by
`https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Character.UnicodeScript.html#forName(java.lang.String)`.


**Blocks** are specified with the prefix `In`, as in
`InMongolian`, or by using the keyword `block` (or its short
form `blk`) as in `block=Mongolian` or `blk=Mongolian`.


The block names supported by `Pattern` are the valid block names
accepted and defined by
`https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Character.UnicodeBlock.html#forName(java.lang.String)`.


**Categories** may be specified with the optional prefix `Is`:
Both `\p{L}` and `\p{IsL}` denote the category of Unicode
letters. Same as scripts and blocks, categories can also be specified
by using the keyword `general_category` (or its short form
`gc`) as in `general_category=Lu` or `gc=Lu`.


The supported categories are those of
[*The Unicode Standard*](http://www.unicode.org/unicode/standard/standard.html) in the version specified by the
`https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Character.html` class. The category names are those
defined in the Standard, both normative and informative.


**Binary properties** are specified with the prefix `Is`, as in
`IsAlphabetic`. The supported binary properties by `Pattern`
are

- Alphabetic
- Ideographic
- Letter
- Lowercase
- Uppercase
- Titlecase
- Punctuation
- Control
- White_Space
- Digit
- Hex_Digit
- Join_Control
- Noncharacter_Code_Point
- Assigned


The following **Predefined Character classes** and **POSIX character classes**
are in conformance with the recommendation of *Annex C: Compatibility Properties*
of [*Unicode Regular Expression *](http://www.unicode.org/reports/tr18/).

| Classes | Matches |
|:---|:---|
| \\p{Lower} | A lowercase character:\\p{IsLowercase} |
| \\p{Upper} | An uppercase character:\\p{IsUppercase} |
| \\p{ASCII} | All ASCII:\[\\x00-\\x7F\] |
| \\p{Alpha} | An alphabetic character:\\p{IsAlphabetic} |
| \\p{Digit} | A decimal digit character:p{IsDigit} |
| \\p{Alnum} | An alphanumeric character:\[\\p{IsAlphabetic}\\p{IsDigit}\] |
| \\p{Punct} | A punctuation character:p{IsPunctuation} |
| \\p{Graph} | A visible character: \[\^\\p{IsWhite_Space}\\p{gc=Cc}\\p{gc=Cs}\\p{gc=Cn}\] |
| \\p{Print} | A printable character: `[\p{Graph}\p{Blank}&&[^\p{Cntrl}]]` |
| \\p{Blank} | A space or a tab: `[\p{IsWhite_Space}&&[^\p{gc=Zl}\p{gc=Zp}\x0a\x0b\x0c\x0d\x85]]` |
| \\p{Cntrl} | A control character: \\p{gc=Cc} |
| \\p{XDigit} | A hexadecimal digit: \[\\p{gc=Nd}\\p{IsHex_Digit}\] |
| \\p{Space} | A whitespace character:\\p{IsWhite_Space} |
| \\d | A digit: \\p{IsDigit} |
| \\D | A non-digit: \[\^\\d\] |
| \\s | A whitespace character: \\p{IsWhite_Space} |
| \\S | A non-whitespace character: \[\^\\s\] |
| \\w | A word character: \[\\p{Alpha}\\p{gc=Mn}\\p{gc=Me}\\p{gc=Mc}\\p{Digit}\\p{gc=Pc}\\p{IsJoin_Control}\] |
| \\W | A non-word character: \[\^\\w\] |


Categories that behave like the java.lang.Character
boolean is*methodname* methods (except for the deprecated ones) are
available through the same \\p{*prop*} syntax where
the specified property has the name java*methodname*.

### Comparison to Perl 5

The `Pattern` engine performs traditional NFA-based matching
with ordered alternation as occurs in Perl 5.

Perl constructs not supported by this class:

- Predefined character classes (Unicode character)

  \\X Match Unicode
  [*extended grapheme cluster*](http://www.unicode.org/reports/tr18/#Default_Grapheme_Clusters)
- The backreference constructs, \\g{*n*} for
  the *n*^th^[capturing group](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#cg) and
  \\g{*name*} for
  [named-capturing group](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#groupname).

- The named character construct, \\N{*name*}
  for a Unicode character by its name.

- The conditional constructs
  (?(*condition*)*X*) and
  (?(*condition*)*X*\|*Y*),

- The embedded code constructs (?{*code*})
  and (??{*code*}),

- The embedded comment syntax (?#comment), and

- The preprocessing operations \\l \\u,
  \\L, and \\U.

Constructs supported by this class but not by Perl:

- Character-class union and intersection as described
  [above](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern#cc).

Notable differences from Perl:

- In Perl, \\1 through \\9 are always interpreted
  as back references; a backslash-escaped number greater than 9 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,
  \\1 through \\9 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.

- Perl uses the g flag to request a match that resumes
  where the last match left off. This functionality is provided implicitly
  by the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Matcher.html` class: Repeated invocations of the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Matcher.html#find()` method will resume where the last match left off,
  unless the matcher is reset.

- 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.

For a more precise description of the behavior of regular expression
constructs, please see [*Mastering Regular Expressions, 3nd Edition*, Jeffrey E. F. Friedl,
O'Reilly and Associates, 2006.](http://www.oreilly.com/catalog/regex3/)

<br />

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html#split(java.lang.String,%20int)`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html#split(java.lang.String)`

### Constant Summary

|---|---|---|
| int | [CANON_EQ](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#CANON_EQ) | Enables canonical equivalence. |
| int | [CASE_INSENSITIVE](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#CASE_INSENSITIVE) | Enables case-insensitive matching. |
| int | [COMMENTS](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#COMMENTS) | Permits whitespace and comments in pattern. |
| int | [DOTALL](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#DOTALL) | Enables dotall mode. |
| int | [LITERAL](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#LITERAL) | Enables literal parsing of the pattern. |
| int | [MULTILINE](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#MULTILINE) | Enables multiline mode. |
| int | [UNICODE_CASE](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#UNICODE_CASE) | Enables Unicode-aware case folding. |
| int | [UNICODE_CHARACTER_CLASS](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#UNICODE_CHARACTER_CLASS) | Enables the Unicode version of *Predefined character classes* and *POSIX character classes* as defined by [*Unicode Technical Standard #18: Unicode Regular Expression*](http://www.unicode.org/reports/tr18/) *Annex C: Compatibility Properties*. |
| int | [UNIX_LINES](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#UNIX_LINES) | Enables Unix lines mode. |

### Public Method Summary

|---|---|
| [Predicate](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/function/Predicate.html)\<[String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)\> | [asPredicate](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#asPredicate())() Creates a predicate which can be used to match a string. |
| static [Pattern](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html) | [compile](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#compile(java.lang.String))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) regex) Compiles the given regular expression into a pattern. |
| static [Pattern](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html) | [compile](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#compile(java.lang.String,%20int))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) regex, int flags) Compiles the given regular expression into a pattern with the given flags. |
| int | [flags](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#flags())() Returns this pattern's match flags. |
| [Matcher](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Matcher.html) | [matcher](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#matcher(java.lang.CharSequence))([CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input) Creates a matcher that will match the given input against this pattern. |
| static boolean | [matches](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#matches(java.lang.String,%20java.lang.CharSequence))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) regex, [CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input) Compiles the given regular expression and attempts to match the given input against it. |
| [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [pattern](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#pattern())() Returns the regular expression from which this pattern was compiled. |
| static [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [quote](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#quote(java.lang.String))([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) s) Returns a literal pattern `String` for the specified `String`. |
| [String\[\]](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [split](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#split(java.lang.CharSequence,%20int))([CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input, int limit) Splits the given input sequence around matches of this pattern. |
| [String\[\]](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [split](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#split(java.lang.CharSequence))([CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input) Splits the given input sequence around matches of this pattern. |
| [Stream](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/stream/Stream.html)\<[String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)\> | [splitAsStream](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#splitAsStream(java.lang.CharSequence))([CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input) Creates a stream from the given input sequence around matches of this pattern. |
| [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [toString](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#toString())() Returns the string representation of this pattern. |

### Protected Method Summary

|---|---|
| void | [finalize](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#finalize())() Invoked when the garbage collector has detected that this instance is no longer reachable. |

### Inherited Method Summary

From class [java.lang.Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html)

|---|---|
| [Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) | [clone](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#clone())() Creates and returns a copy of this `Object`. |
| boolean | [equals](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#equals(java.lang.Object))([Object](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html) obj) Compares this instance with the specified object and indicates if they are equal. |
| void | [finalize](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#finalize())() Invoked when the garbage collector has detected that this instance is no longer reachable. |
| final [Class](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html)\<?\> | [getClass](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#getClass())() Returns the unique instance of `https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Class.html` that represents this object's class. |
| int | [hashCode](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#hashCode())() Returns an integer hash code for this object. |
| final void | [notify](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#notify())() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up. |
| final void | [notifyAll](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#notifyAll())() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up. |
| [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [toString](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#toString())() Returns a string containing a concise, human-readable description of this object. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait(long,%20int))(long timeout, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait(long))(long timeout) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires. |
| final void | [wait](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Object.html#wait())() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object. |

## Constants

#### public static final int
**CANON_EQ**

Enables canonical equivalence.

When this flag is specified then two characters will be considered
to match if, and only if, their full canonical decompositions match.
The expression "a\\u030A", for example, will match the
string "\\u00E5" when this flag is specified. By default,
matching does not take canonical equivalence into account.

There is no embedded flag character for enabling canonical
equivalence.

Specifying this flag may impose a performance penalty.

<br />

Constant Value: 128

#### public static final int
**CASE_INSENSITIVE**

Enables case-insensitive matching.

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 `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#UNICODE_CASE` flag in conjunction with this flag.

Case-insensitive matching can also be enabled via the embedded flag
expression (?i).

Specifying this flag may impose a slight performance penalty.

<br />

Constant Value: 2

#### public static final int
**COMMENTS**

Permits whitespace and comments in pattern.

In this mode, whitespace is ignored, and embedded comments starting
with # are ignored until the end of a line.

Comments mode can also be enabled via the embedded flag
expression (?x).
Constant Value: 4

#### public static final int
**DOTALL**

Enables dotall mode.

In dotall mode, the expression . matches any character,
including a line terminator. By default this expression does not match
line terminators.

Dotall mode can also be enabled via the embedded flag
expression (?s). (The s is a mnemonic for
"single-line" mode, which is what this is called in Perl.)

<br />

Constant Value: 32

#### public static final int
**LITERAL**

Enables literal parsing of the pattern.

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.

The flags CASE_INSENSITIVE and UNICODE_CASE retain their impact on
matching when used in conjunction with this flag. The other flags
become superfluous.

There is no embedded flag character for enabling literal parsing.
Constant Value: 16

#### public static final int
**MULTILINE**

Enables multiline mode.

In multiline mode the expressions \^ and $ 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.

Multiline mode can also be enabled via the embedded flag
expression (?m).

<br />

Constant Value: 8

#### public static final int
**UNICODE_CASE**

Enables Unicode-aware case folding.

When this flag is specified then case-insensitive matching, when
enabled by the `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#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.

Unicode-aware case folding can also be enabled via the embedded flag
expression (?u).

Specifying this flag may impose a performance penalty.

<br />

Constant Value: 64

#### public static final int
**UNICODE_CHARACTER_CLASS**

Enables the Unicode version of *Predefined character classes* and
*POSIX character classes* as defined by [*Unicode Technical Standard #18: Unicode Regular Expression*](http://www.unicode.org/reports/tr18/)
*Annex C: Compatibility Properties*.


This flag has no effect on Android, unicode character classes are always
used.
Constant Value: 256

#### public static final int
**UNIX_LINES**

Enables Unix lines mode.

In this mode, only the '\\n' line terminator is recognized
in the behavior of ., \^, and $.

Unix lines mode can also be enabled via the embedded flag
expression (?d).
Constant Value: 1

## Public Methods

#### public [Predicate](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/function/Predicate.html)\<[String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)\>
**asPredicate**
()

Creates a predicate which can be used to match a string.

##### Returns

- The predicate which can be used for matching on a string

#### public static [Pattern](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html)
**compile**
([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) regex)

Compiles the given regular expression into a pattern.

##### Parameters

| regex | The expression to be compiled |
|---|---|

##### Returns

- the given regular expression compiled into a pattern

##### Throws

| [PatternSyntaxException](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/PatternSyntaxException.html) | If the expression's syntax is invalid |
|---|---|

#### public static [Pattern](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html)
**compile**
([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) regex, int flags)

Compiles the given regular expression into a pattern with the given
flags.

##### Parameters

| regex | The expression to be compiled |
| flags | Match flags, a bit mask that may include `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#CASE_INSENSITIVE`, `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#MULTILINE`, `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#DOTALL`, `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#UNICODE_CASE`, `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#CANON_EQ`, `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#UNIX_LINES`, `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#LITERAL`, `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#UNICODE_CHARACTER_CLASS` and `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#COMMENTS` |
|---|---|

##### Returns

- the given regular expression compiled into a pattern with the given flags

##### Throws

| [IllegalArgumentException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/IllegalArgumentException.html) | If bit values other than those corresponding to the defined match flags are set in flags |
| [PatternSyntaxException](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/PatternSyntaxException.html) | If the expression's syntax is invalid |
|---|---|

#### public int
**flags**
()

Returns this pattern's match flags.

##### Returns

- The match flags specified when this pattern was compiled

#### public [Matcher](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Matcher.html)
**matcher**
([CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input)

Creates a matcher that will match the given input against this pattern.

##### Parameters

| input | The character sequence to be matched |
|---|---|

##### Returns

- A new matcher for this pattern

#### public static boolean
**matches**
([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) regex, [CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input)

Compiles the given regular expression and attempts to match the given
input against it.

An invocation of this convenience method of the form

> ```
>  Pattern.matches(regex, input);
> ```
behaves in exactly the same way as the expression
>
> ```
>  Pattern.compile(regex).matcher(input).matches()
> ```

If a pattern is to be used multiple times, compiling it once and reusing
it will be more efficient than invoking this method each time.

<br />

##### Parameters

| regex | The expression to be compiled |
| input | The character sequence to be matched |
|---|---|

##### Returns

- whether or not the regular expression matches on the input

##### Throws

| [PatternSyntaxException](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/PatternSyntaxException.html) | If the expression's syntax is invalid |
|---|---|

#### public [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)
**pattern**
()

Returns the regular expression from which this pattern was compiled.

##### Returns

- The source of this pattern

#### public static [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)
**quote**
([String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) s)

Returns a literal pattern `String` for the specified
`String`.

This method produces a `String` that can be used to
create a `Pattern` that would match the string
`s` as if it were a literal pattern.
Metacharacters or escape sequences in the input sequence will be given no special meaning.

<br />

##### Parameters

| s | The string to be literalized |
|---|---|

##### Returns

- A literal string replacement

#### public [String\[\]](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)
**split**
([CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input, int limit)

Splits the given input sequence around matches of this pattern.

The array returned by this method contains each substring of the
input sequence that is terminated by another subsequence that matches
this pattern or is terminated by the end of the input sequence. The
substrings in the array are in the order in which they occur in the
input. If this pattern does not match any subsequence of the input then
the resulting array has just one element, namely the input sequence in
string form.

When there is a positive-width match at the beginning of the input
sequence then an empty leading substring is included at the beginning
of the resulting array. A zero-width match at the beginning however
can only produce such an empty leading substring for apps running on or
targeting API versions \<= 28.

The limit parameter controls the number of times the
pattern is applied and therefore affects the length of the resulting
array. If the limit *n* is greater than zero then the pattern
will be applied at most *n* - 1 times, the array's
length will be no greater than *n*, and the array's last entry
will contain all input beyond the last matched delimiter. If *n*
is non-positive then the pattern will be applied as many times as
possible and the array can have any length. If *n* is zero then
the pattern will be applied as many times as possible, the array can
have any length, and trailing empty strings will be discarded.

The input "boo:and:foo", for example, yields the following
results with these parameters:

> | *Regex * | *Limit * | *Result * |
> |:---|:---|:---|
> | : | 2 | { "boo", "and:foo" } |
> | : | 5 | { "boo", "and", "foo" } |
> | : | -2 | { "boo", "and", "foo" } |
> | o | 5 | { "b", "", ":and:f", "", "" } |
> | o | -2 | { "b", "", ":and:f", "", "" } |
> | o | 0 | { "b", "", ":and:f" } |

<br />

##### Parameters

| input | The character sequence to be split |
| limit | The result threshold, as described above |
|---|---|

##### Returns

- The array of strings computed by splitting the input around matches of this pattern

#### public [String\[\]](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)
**split**
([CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input)

Splits the given input sequence around matches of this pattern.

This method works as if by invoking the two-argument `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#split(java.lang.CharSequence,%20int)` method with the given input
sequence and a limit argument of zero. Trailing empty strings are
therefore not included in the resulting array.

The input "boo:and:foo", for example, yields the following
results with these expressions:

> | *Regex * | *Result* |
> |:---|:---|
> | : | { "boo", "and", "foo" } |
> | o | { "b", "", ":and:f" } |

<br />

##### Parameters

| input | The character sequence to be split |
|---|---|

##### Returns

- The array of strings computed by splitting the input around matches of this pattern

#### public [Stream](https://developers.google.com/j2objc/javadoc/jre/reference/java/util/stream/Stream.html)\<[String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)\>
**splitAsStream**
([CharSequence](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/CharSequence.html) input)

Creates a stream from the given input sequence around matches of this
pattern.

The stream returned by this method contains each substring of the
input sequence that is terminated by another subsequence that matches
this pattern or is terminated by the end of the input sequence. The
substrings in the stream are in the order in which they occur in the
input. Trailing empty strings will be discarded and not encountered in
the stream.

If this pattern does not match any subsequence of the input then
the resulting stream has just one element, namely the input sequence in
string form.

When there is a positive-width match at the beginning of the input
sequence then an empty leading substring is included at the beginning
of the stream. A zero-width match at the beginning however never produces
such empty leading substring.

If the input sequence is mutable, it must remain constant during the
execution of the terminal stream operation. Otherwise, the result of the
terminal stream operation is undefined.

##### Parameters

| input | The character sequence to be split |
|---|---|

##### Returns

- The stream of strings computed by splitting the input around matches of this pattern

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/util/regex/Pattern.html#split(java.lang.CharSequence)`

#### public [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)
**toString**
()

<br />

Returns the string representation of this pattern. This
is the regular expression from which this pattern was
compiled.

<br />

##### Returns

- The string representation of this pattern

## Protected Methods

#### protected void
**finalize**
()

Invoked when the garbage collector has detected that this instance is no longer reachable.
The default implementation does nothing, but this method can be overridden to free resources.

Note that objects that override `finalize` are significantly more expensive than
objects that don't. Finalizers may be run a long time after the object is no longer
reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup.
Note also that finalizers are run on a single VM-wide finalizer thread,
so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary
for a class that has a native peer and needs to call a native method to destroy that peer.
Even then, it's better to provide an explicit `close` method (and implement
`https://developers.google.com/j2objc/javadoc/jre/reference/java/io/Closeable.html`), and insist that callers manually dispose of instances. This
works well for something like files, but less well for something like a `BigInteger`
where typical calling code would have to deal with lots of temporaries. Unfortunately,
code that creates lots of temporaries is the worst kind of code from the point of view of
the single finalizer thread.

If you *must* use finalizers, consider at least providing your own
`https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ref/ReferenceQueue.html` and having your own thread process that queue.

Unlike constructors, finalizers are not automatically chained. You are responsible for
calling `super.finalize()` yourself.

Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer
thread.

See *Effective Java* Item 7, "Avoid finalizers" for more.

##### Throws

| [Throwable](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/Throwable.html) |   |
|---|---|