Pattern  |  API reference  |  Android Developers (original) (raw)

public final class Pattern
extends [Object](/reference/java/lang/Object) implements[Serializable](/reference/java/io/Serializable)

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 [Matcher](/reference/java/util/regex/Matcher) object that can match arbitrary 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.[compile](/reference/java/util/regex/Pattern#compile%28java.lang.String%29)("a*b"); Matcher m = p.[matcher](/reference/java/util/regex/Pattern#matcher%28java.lang.CharSequence%29)("aaaaab"); boolean b = m.[matches](/reference/java/util/regex/Matcher#matches%28%29)();

A [matches](/reference/java/util/regex/Pattern#matches%28java.lang.String,%20java.lang.CharSequence%29) 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 [Matcher](/reference/java/util/regex/Matcher) class are not safe for such use.

Summary of regular-expression constructs

dmsuxU on - off

Regular expression constructs, and what they match

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_ (Character.MIN_CODE_POINT <= 0x_h...h_ <= Character.MAX_CODE_POINT)
\N{name} The character with Unicode character name 'name'
\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
Character classes
[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)
Predefined character classes
. Any character (may or may not match line terminators)
\d A digit: \p{IsDigit}
\D A non-digit: [^\d]
\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: \p{IsWhite_Space}
\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: [\p{alpha}\p{gc=Mark}\p{digit}\p{gc=Connector_Punctuation}\p{Join_Control}]
\W A non-word character: [^\w]
POSIX character classes (Unicode-aware)
\p{Lower} A lower-case alphabetic character: \p{IsLowercase}
\p{Upper} An upper-case alphabetic character:\p{IsUppercase}
\p{ASCII} All ASCII:[\x00-\x7F]
\p{Alpha} An alphabetic character:[\p{IsAlphabetic}]
\p{IsDigit} A decimal digit: \p{gc=Decimal_Number}
\p{Alnum} An alphanumeric character:[\p{Alpha}\p{Digit}]
\p{Punct} Punctuation: \p{IsPunctuation}
\p{Graph} A visible character:[^p{space}\p{gc=Control}\p{gc=Surrogate}\p{gc=Unassigned}]
\p{Print} A printable character: [\p{Graph}\p{Blank}&&[^\p{Cntrl}]]
\p{Blank} A space or a tab: [\p{gc=Space_Separator}\N{CHARACTER TABULATION}]
\p{Cntrl} A control character: \p{gc=Control}
\p{XDigit} A hexadecimal digit: [\p{gc=Decimal_Number}\p{IsHex_Digit}]
\p{Space} A whitespace character: \p{IsWhite_Space}
POSIX-Compatible expression See Unicode documentation
java.lang.Character classes (simple java character type)
\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()
Classes for Unicode scripts, blocks, categories and binary properties
\p{IsLatin} A Latin script character (script)
\p{InGreek} A character in the Greek block (block)
\p{Lu} An uppercase letter (category)
\p{IsAlphabetic} An alphabetic character (binary property)
\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)
Boundary matchers
^ 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 finalterminator, if any
\z The end of the input
Linebreak matcher
\R Any Unicode linebreak sequence, is equivalent to\u000D\u000A|[\u000A\u000B\u000C\u000D\u0085\u2028\u2029]
Unicode Extended Grapheme matcher
\X Any Unicode extended grapheme cluster
Greedy quantifiers
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
Reluctant quantifiers
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
Possessive quantifiers
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
Logical operators
XY X followed by Y
X|Y Either X or Y
(X) X, as a capturing group
Back references
\n Whatever the _n_th capturing group matched
\k<_name_> Whatever thenamed-capturing group "name" matched. Only available for API 26 or above
Quotation
\ Nothing, but quotes the following character
\Q Nothing, but quotes all characters until \E
\E Nothing, but ends quoting started by \Q
Special constructs (named-capturing and non-capturing)
(?<name>X) X, as a named-capturing group. Only available for API 26 or above.
(?:X) X, as a non-capturing group
(?idmsux-idmsux)
(?idmsuxU-idmsuxU:X) X, as a non-capturing group with the given flags i d m s u x U 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 byThe Java Language Specification as either Unicode escapes (section {@jls 3.3}) or other character escapes (section {@jls 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:

Precedence of character class operators.

Precedence Name Example
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. Any Unicode linebreak sequence '\R' is recognized as line terminator. In particular, on Android, the following are also recognized as line terminators:

If [UNIX_LINES](/reference/java/util/regex/Pattern#UNIX%5FLINES) mode is activated, then the only line terminators recognized are newline characters.

The regular expression . matches any character except a line terminator unless the [DOTALL](/reference/java/util/regex/Pattern#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 [MULTILINE](/reference/java/util/regex/Pattern#MULTILINE) mode is activated then^ matches at the beginning of input and after any line terminator except at the end of input. When in [MULTILINE](/reference/java/util/regex/Pattern#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.

A named-capturing group is still numbered as described inGroup number.

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 Expressions, plus RL2.1 Canonical Equivalents and RL2.2 Extended Grapheme Clusters.

Unicode escape sequences such as \u2014 in Java source code are processed as described in section {@jls 3.3} ofThe 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 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 character names are supported by the named character construct\N{...}, for example, \N{WHITE SMILING FACE} specifies character \u263A. The character names supported by this class are the valid Unicode character names matched byjava.lang.Character.codePointOf(String) Character.codePointOf(name).

Unicode extended grapheme clusters are supported by the grapheme cluster matcher \X.

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 supported since Android 10, 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[UnicodeScript.forName](/reference/java/lang/Character.UnicodeScript#forName%28java.lang.String%29).

Blocks are specified with the prefix In, as inInMongolian, 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[UnicodeBlock.forName](/reference/java/lang/Character.UnicodeBlock#forName%28java.lang.String%29).

Categories may be specified with the optional prefix Is: Both \p{IsL} supported since Android 10 and \p{L} 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 formgc) as in general_category=Lu or gc=Lu.

The supported categories are those of The Unicode Standard in the version specified by the[Character](/reference/java/lang/Character) class. The category names are those defined in the Standard, both normative and informative.

Binary properties are specified with the prefix Is since Android 10, as in IsAlphabetic. The prefix Is isn't needed before Android 10, as in Alphabetic. The supported binary properties by Pattern are

The Predefined Character classes and POSIX character classes are in conformance with the recommendation of Annex C: Compatibility Properties of Unicode Technical Standard #18: Unicode Regular Expressions.

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_.

Behavior starting from API level 10 (Android 2.3)

Starting from Android 2.3 Gingerbread, ICU4C becomes the backend of the regular expression implementation. Android could behave differently compared with other regex implementation, e.g. literal right brace ('}') has to be escaped on Android.

Some other behavior differences can be found in the ICU documentation.

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:

Constructs supported by this class but not by Perl:

Notable differences from Perl:

For a more precise description of the behavior of regular expression constructs, please see Mastering Regular Expressions, 3rd Edition, Jeffrey E. F. Friedl, O'Reilly and Associates, 2006.

Summary

Constants
int CANON_EQ This flag is not supported on Android.
int CASE_INSENSITIVE Enables case-insensitive matching.
int COMMENTS Permits whitespace and comments in pattern.
int DOTALL Enables dotall mode.
int LITERAL Enables literal parsing of the pattern.
int MULTILINE Enables multiline mode.
int UNICODE_CASE Enables Unicode-aware case folding.
int UNICODE_CHARACTER_CLASS This flag is not supported on Android, and Unicode character classes are always used.
int UNIX_LINES Enables Unix lines mode.
Public methods
Predicate<String> asMatchPredicate() Creates a predicate that tests if this pattern matches a given input string.
Predicate<String> asPredicate() Creates a predicate that tests if this pattern is found in a given input string.
staticPattern compile(String regex) Compiles the given regular expression into a pattern.
staticPattern compile(String regex, int flags) Compiles the given regular expression into a pattern with the given flags.
int flags() Returns this pattern's match flags.
Matcher matcher(CharSequence input) Creates a matcher that will match the given input against this pattern.
static boolean matches(String regex, CharSequence input) Compiles the given regular expression and attempts to match the given input against it.
String pattern() Returns the regular expression from which this pattern was compiled.
staticString quote(String s) Returns a literal pattern String for the specifiedString.
String[] split(CharSequence input, int limit) Splits the given input sequence around matches of this pattern.
String[] split(CharSequence input) Splits the given input sequence around matches of this pattern.
Stream<String> splitAsStream(CharSequence input) Creates a stream from the given input sequence around matches of this pattern.
String toString() Returns the string representation of this pattern.
Inherited methods
From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. finalClass<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Constants

CANON_EQ

public static final int CANON_EQ

This flag is not supported on Android.

Constant Value: 128 (0x00000080)

CASE_INSENSITIVE

public static final int CASE_INSENSITIVE

Enables case-insensitive matching.

Case-insensitive matching is Unicode-aware on Android.

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

Specifying this flag may impose a slight performance penalty.

Constant Value: 2 (0x00000002)

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 (0x00000004)

DOTALL

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.)

Constant Value: 32 (0x00000020)

LITERAL

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 (0x00000010)

MULTILINE

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).

Constant Value: 8 (0x00000008)

UNICODE_CASE

public static final int UNICODE_CASE

Enables Unicode-aware case folding. This flag is ignoredon Android. When [CASE_INSENSITIVE](/reference/java/util/regex/Pattern#CASE%5FINSENSITIVE) flag is provided, case-insensitive matching is always done in a manner consistent with the Unicode Standard.

The embedded flag (?u) is ignored.

Specifying this flag may impose a performance penalty.

Constant Value: 64 (0x00000040)

UNICODE_CHARACTER_CLASS

public static final int UNICODE_CHARACTER_CLASS

This flag is not supported on Android, and Unicode character classes are always used.

See the Unicode version of_Predefined character classes_ and POSIX character classes are in conformance withUnicode Technical Standard #18: Unicode Regular Expressions Annex C: Compatibility Properties.

Constant Value: 256 (0x00000100)

UNIX_LINES

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 (0x00000001)

Public methods

asMatchPredicate

public Predicate<String> asMatchPredicate ()

Creates a predicate that tests if this pattern matches a given input string.

API Note:
s -> matcher(s).matches();
Returns
Predicate<String> The predicate which can be used for matching an input string against this pattern.

asPredicate

public Predicate<String> asPredicate ()

Creates a predicate that tests if this pattern is found in a given input string.

API Note:
s -> matcher(s).find();
Returns
Predicate<String> The predicate which can be used for finding a match on a subsequence of a string

compile

public static Pattern compile (String regex)

Compiles the given regular expression into a pattern.

Parameters
regex String: The expression to be compiled
Returns
Pattern the given regular expression compiled into a pattern
Throws
PatternSyntaxException If the expression's syntax is invalid

flags

public int flags ()

Returns this pattern's match flags.

Returns
int The match flags specified when this pattern was compiled

matcher

public Matcher matcher (CharSequence input)

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

Parameters
input CharSequence: The character sequence to be matched
Returns
Matcher A new matcher for this pattern

matches

public static boolean matches (String regex, CharSequence 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.

Parameters
regex String: The expression to be compiled
input CharSequence: The character sequence to be matched
Returns
boolean whether or not the regular expression matches on the input
Throws
PatternSyntaxException If the expression's syntax is invalid

pattern

public String pattern ()

Returns the regular expression from which this pattern was compiled.

Returns
String The source of this pattern

quote

public static String quote (String s)

Returns a literal pattern String for the specifiedString.

This method produces a String that can be used to create a Pattern that would match the strings as if it were a literal pattern.

Metacharacters or escape sequences in the input sequence will be given no special meaning.

Parameters
s String: The string to be literalized
Returns
String A literal string replacement

split

public String[] split (CharSequence 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.

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

Split example showing regex, limit, and result

Regex Limit Result
: 2 { "boo", "and:foo" }
5 { "boo", "and", "foo" }
-2 { "boo", "and", "foo" }
o 5 { "b", "", ":and:f", "", "" }
-2 { "b", "", ":and:f", "", "" }
0 { "b", "", ":and:f" }
Parameters
input CharSequence: The character sequence to be split
limit int: The result threshold, as described above
Returns
String[] The array of strings computed by splitting the input around matches of this pattern

split

public String[] split (CharSequence input)

Splits the given input sequence around matches of this pattern.

This method works as if by invoking the two-argument [split](/reference/java/util/regex/Pattern#split%28java.lang.CharSequence,%20int%29) 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:

Split examples showing regex and result

Regex Result
: { "boo", "and", "foo" }
o { "b", "", ":and:f" }
Parameters
input CharSequence: The character sequence to be split
Returns
String[] The array of strings computed by splitting the input around matches of this pattern

splitAsStream

public Stream<String> splitAsStream (CharSequence 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 CharSequence: The character sequence to be split
Returns
Stream<String> The stream of strings computed by splitting the input around matches of this pattern

toString

public String toString ()

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

Returns
String The string representation of this pattern