java.util.regex.Pattern
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java.lang.Object
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 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("a*b"); Matcher m = p.matcher("aaaaab"); boolean b = m.matches();
A 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
boolean b = Pattern.matches("a*b", "aaaaab"); Instances of this class are immutable and are safe for use by multiple
concurrent threads. Instances of the Matcher class are not safe for
such use.
Summary of regular-expression constructs
| Construct | Matches |
|---|---|
| Characters | |
| x | The character x |
| \\ | The backslash character |
| \0n | The character with octal value 0n (0 <= n <= 7) |
| \0nn | The character with octal value 0nn (0 <= n <= 7) |
| \0mnn | The character with octal value 0mnn (0 <= m <= 3, 0 <= n <= 7) |
| \xhh | The character with hexadecimal value 0xhh |
| \uhhhh | The character with hexadecimal value 0xhhhh |
| \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') |
| \cx | 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: [0-9] |
| \D | A non-digit: [^0-9] |
| \s | A whitespace character: [ \t\n\x0B\f\r] |
| \S | A non-whitespace character: [^\s] |
| \w | A word character: [a-zA-Z_0-9] |
| \W | A non-word character: [^\w] |
| POSIX character classes (US-ASCII only) | |
| \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}] |
| \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] |
| Classes for Unicode blocks and categories | |
| \p{InGreek} | A character in the Greek block (simple block) |
| \p{Lu} | An uppercase letter (simple category) |
| \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 final terminator, if any |
| \z | The end of the input |
| 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 nth capturing group matched |
| 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 (non-capturing) | |
| (?:X) | X, as a non-capturing group |
| (?idmsux-idmsux) | Nothing, but turns match flags on - off |
| (?idmsux-idmsux:X) | X, as a non-capturing group with the given flags 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 |
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 or other character
escapes. 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 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:
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.
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:
If The regular expression . matches any character except a line
terminator unless the 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 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: 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.
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 pure, non-capturing groups
that do not capture text and do not count towards the group total.
This class follows Unicode Technical
Report #18: Unicode Regular Expression Guidelines, implementing its
second level of support though with a slightly different concrete syntax.
Unicode escape sequences such as \u2014 in Java source code
are processed as described in §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.
Unicode blocks and categories 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. Blocks are specified with the prefix
In, as in InMongolian. Categories may be specified with
the optional prefix Is: Both \p{L} and \p{IsL}
denote the category of Unicode letters. Blocks and categories can be used
both inside and outside of a character class.
The supported blocks and categories are those of The Unicode
Standard, Version 3.0. The block names are those defined in
Chapter 14 and in the file Blocks-3.txt
of the Unicode
Character Database except that the spaces are removed; "Basic
Latin", for example, becomes "BasicLatin". The category names
are those defined in table 4-5 of the Standard (p. 88), both normative
and informative.
Perl constructs not supported by this class: The conditional constructs (?{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: Possessive quantifiers, which greedily match as much as they can
and do not back off, even when doing so would allow the overall match to
succeed. Character-class union and intersection as described
above. 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 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. Perl is forgiving about malformed matching constructs, as in the
expression *a, as well as dangling brackets, as in the
expression abc], and treats them as literals. This
class also accepts dangling brackets but is strict about dangling
metacharacters like +, ? and *, and will throw a
For a more precise description of the behavior of regular expression
constructs, please see
Mastering Regular Expressions, 2nd Edition, Jeffrey E. F. Friedl,
O'Reilly and Associates, 2002.
Character Classes
1
Literal escape
\x 2
Grouping
[...] 3
Range
a-z 4
Union
[a-e][i-u] 5
Intersection
[a-z&&[aeiou]] Line terminators
UNIX_LINES mode is activated, then the only line terminators
recognized are newline characters.
DOTALL flag is specified.
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 mode $
matches just before a line terminator or the end of the input sequence.
Groups and capturing
1
((A)(B(C))) 2
(A) 3
(B(C)) 4
(C) Unicode support
Comparison to Perl 5
Matcher class: Repeated invocations of the find method will resume where the last match left off,
unless the matcher is reset. PatternSyntaxException if it encounters them.
String.split(String, int),
String.split(String),
Serialized Form
| Nested Class Summary | |
(package private) static class |
Pattern.Add
An object added to the tree when a character class has an additional range added to it. |
(package private) static class |
Pattern.All
Implements the Unicode category ALL and the dot metacharacter when in dotall mode. |
(package private) static class |
Pattern.BackRef
Refers to a group in the regular expression. |
(package private) static class |
Pattern.Begin
Node to anchor at the beginning of input. |
(package private) static class |
Pattern.Behind
Zero width positive lookbehind. |
(package private) static class |
Pattern.BitClass
Creates a bit vector for matching ASCII values. |
(package private) static class |
Pattern.BnM
Attempts to match a slice in the input using the Boyer-Moore string matching algorithm. |
(package private) static class |
Pattern.Both
An object added to the tree when a character class has another nested class in it. |
(package private) static class |
Pattern.Bound
Handles word boundaries. |
(package private) static class |
Pattern.Branch
Handles the branching of alternations. |
(package private) static class |
Pattern.Caret
Node to anchor at the beginning of a line. |
(package private) static class |
Pattern.Category
Node class that matches a Unicode category. |
(package private) static class |
Pattern.CIBackRef
|
(package private) static class |
Pattern.CINotRange
|
(package private) static class |
Pattern.CIRange
Node class for matching characters within an explicit value range in a case insensitive manner. |
(package private) static class |
Pattern.Conditional
|
(package private) static class |
Pattern.Ctype
Node class that matches a POSIX type. |
(package private) static class |
Pattern.Curly
Handles the curly-brace style repetition with a specified minimum and maximum occurrences. |
(package private) static class |
Pattern.Dollar
Node to anchor at the end of a line or the end of input based on the multiline mode. |
(package private) static class |
Pattern.Dot
Node class for the dot metacharacter when dotall is not enabled. |
(package private) static class |
Pattern.Dummy
Dummy node to assist in connecting branches. |
(package private) static class |
Pattern.End
Node to anchor at the end of input. |
(package private) static class |
Pattern.First
Searches until the next instance of its atom. |
(package private) static class |
Pattern.GroupCurly
Handles the curly-brace style repetition with a specified minimum and maximum occurrences in deterministic cases. |
(package private) static class |
Pattern.GroupHead
The GroupHead saves the location where the group begins in the locals and restores them when the match is done. |
(package private) static class |
Pattern.GroupRef
Recursive reference to a group in the regular expression. |
(package private) static class |
Pattern.GroupTail
The GroupTail handles the setting of group beginning and ending locations when groups are successfully matched. |
(package private) static class |
Pattern.LastMatch
Node to match the location where the last match ended. |
(package private) static class |
Pattern.LastNode
|
(package private) static class |
Pattern.LazyLoop
Handles the repetition count for a reluctant Curly. |
(package private) static class |
Pattern.Loop
Handles the repetition count for a greedy Curly. |
(package private) static class |
Pattern.Neg
Zero width negative lookahead. |
(package private) static class |
Pattern.Node
Base class for all node classes. |
(package private) static class |
Pattern.Not
|
(package private) static class |
Pattern.NotBehind
Zero width negative lookbehind. |
(package private) static class |
Pattern.NotCtype
|
(package private) static class |
Pattern.NotRange
|
(package private) static class |
Pattern.NotSingle
Node class to match any character except a single char value. |
(package private) static class |
Pattern.NotSingleA
|
(package private) static class |
Pattern.NotSingleU
Case independent unicode value. |
(package private) static class |
Pattern.Pos
Zero width positive lookahead. |
(package private) static class |
Pattern.Prolog
This sets up a loop to handle a recursive quantifier structure. |
(package private) static class |
Pattern.Ques
The 0 or 1 quantifier. |
(package private) static class |
Pattern.Range
Node class for matching characters within an explicit value range. |
(package private) static class |
Pattern.Single
Node class for a single character value. |
(package private) static class |
Pattern.SingleA
Case independent ASCII value. |
(package private) static class |
Pattern.SingleU
Case independent unicode value. |
(package private) static class |
Pattern.Slice
Node class for a case sensitive sequence of literal characters. |
(package private) static class |
Pattern.SliceA
Node class for a case insensitive sequence of literal characters. |
(package private) static class |
Pattern.SliceU
Node class for a case insensitive sequence of literal characters. |
(package private) static class |
Pattern.Specials
|
(package private) static class |
Pattern.Start
Used for REs that can start anywhere within the input string. |
(package private) static class |
Pattern.Sub
An object added to the tree when a character class has a range or single subtracted from it. |
(package private) static class |
Pattern.TreeInfo
Used to accumulate information about a subtree of the object graph so that optimizations can be applied to the subtree. |
(package private) static class |
Pattern.UnixCaret
Node to anchor at the beginning of a line when in unixdot mode. |
(package private) static class |
Pattern.UnixDollar
Node to anchor at the end of a line or the end of input based on the multiline mode when in unix lines mode. |
(package private) static class |
Pattern.UnixDot
Node class for the dot metacharacter when dotall is not enabled but UNIX_LINES is enabled. |
| Field Summary | |
(package private) static Pattern.Node |
accept
This must be the very first initializer. |
(package private) char[] |
buffer
Temporary storage used by parsing pattern slice. |
static int |
CANON_EQ
Enables canonical equivalence. |
static int |
CASE_INSENSITIVE
Enables case-insensitive matching. |
(package private) static HashMap |
categories
|
private static String[] |
categoryNames
|
private static Pattern.Node[] |
categoryNodes
|
static int |
COMMENTS
Permits whitespace and comments in pattern. |
private int |
cursor
Index into the pattern string that keeps track of how much has been parsed. |
static int |
DOTALL
Enables dotall mode. |
(package private) static HashMap |
families
|
private static String[] |
familyNames
Static template for all character families. |
private static Pattern.Node[] |
familyNodes
|
private int |
flags
The original pattern flags. |
(package private) static int |
GREEDY
|
(package private) int |
groupCount
The group count of this Pattern. |
(package private) Pattern.GroupHead[] |
groupNodes
Temporary storage used while parsing group references. |
(package private) static int |
INDEPENDENT
|
(package private) static Pattern.Node |
lastAccept
|
(package private) static int |
LAZY
|
(package private) int |
localCount
The local variable count used by parsing tree. |
(package private) Pattern.Node |
matchRoot
The root of object tree for a match operation. |
(package private) static int |
MAX_REPS
|
static int |
MULTILINE
Enables multiline mode. |
private String |
normalizedPattern
The normalized pattern string. |
private String |
pattern
The original regular-expression pattern string. |
private int |
patternLength
Holds the length of the pattern string. |
(package private) static int |
POSSESSIVE
|
(package private) Pattern.Node |
root
The starting point of state machine for the find operation. |
private static long |
serialVersionUID
use serialVersionUID from Merlin b59 for interoperability |
private char[] |
temp
Temporary null terminating char array used by pattern compiling. |
static int |
UNICODE_CASE
Enables Unicode-aware case folding. |
static int |
UNIX_LINES
Enables Unix lines mode. |
| Constructor Summary | |
private |
Pattern(String p,
int f)
This private constructor is used to create all Patterns. |
| Method Summary | |
private void |
accept(int ch,
String s)
Match next character, signal error if failed. |
private void |
addFlag()
Parses inlined match flags and set them appropriately. |
private void |
append(int ch,
int len)
|
private Pattern.Node |
atom()
Parse and add a new Single or Slice. |
private int |
c()
Utility method for parsing control escape sequences. |
private Pattern.Node |
clazz(boolean consume)
Parse a character class, and return the node that matches it. |
private Pattern.Node |
closure(Pattern.Node prev)
Processes repetition. |
private void |
compile()
Copies regular expression to a char array and inovkes the parsing of the expression which will create the object tree. |
static Pattern |
compile(String regex)
Compiles the given regular expression into a pattern. |
static Pattern |
compile(String regex,
int flags)
Compiles the given regular expression into a pattern with the given flags. |
private String |
composeOneStep(String input)
Attempts to compose input by combining the first character with the first combining mark following it. |
private Pattern.Node |
createGroup(boolean anonymous)
Create group head and tail nodes using double return. |
private Pattern.Node |
error(String s)
Internal method used for handling all syntax errors. |
private int |
escape(boolean inclass,
boolean create)
Parses an escape sequence to determine the actual value that needs to be matched. |
private Pattern.Node |
expr(Pattern.Node end)
The expression is parsed with branch nodes added for alternations. |
private Pattern.Node |
family(boolean not,
boolean singleLetter)
Parses a Unicode character family and returns its representative node. |
private Pattern.Node |
familyError(String name,
String type)
|
int |
flags()
Returns this pattern's match flags. |
private int |
getClass(char c)
|
private Pattern.Node |
group0()
Parses a group and returns the head node of a set of nodes that process the group. |
private boolean |
has(int f)
Indicates whether a particular flag is set or not. |
private boolean |
isLineSeparator(int ch)
Determines if character is a line separator in the current mode |
private void |
mark(char c)
Mark the end of pattern with a specific character. |
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. |
private Pattern.Node |
newSingle(int ch)
Utility method for creating a single character matcher. |
private Pattern.Node |
newSlice(char[] buf,
int count)
Utility method for creating a string slice matcher. |
private int |
next()
Advance the cursor by one, and peek the next character. |
private int |
nextEscaped()
Advance the cursor by one, and peek the next character, ignoring the COMMENTS setting |
private void |
normalize()
The pattern is converted to normalizedD form and then a pure group is constructed to match canonical equivalences of the characters. |
private int |
normalizeCharClass(StringBuffer newPattern,
int i)
Complete the character class being parsed and add a set of alternations to it that will match the canonical equivalences of the characters within the class. |
private int |
o()
Utility method for parsing octal escape sequences. |
private int |
parsePastLine()
xmode parse past comment to end of line. |
private int |
parsePastWhitespace(int ch)
If in xmode parse past whitespace and comments. |
String |
pattern()
Returns the regular expression from which this pattern was compiled. |
private int |
peek()
Peek the next character, and do not advance the cursor. |
private int |
peekPastLine()
xmode peek past comment to end of line. |
private int |
peekPastWhitespace(int ch)
If in xmode peek past whitespace and comments. |
private static void |
printObjectTree(Pattern.Node node)
Used to print out a subtree of the Pattern to help with debugging. |
private String |
produceEquivalentAlternation(String source)
Given a specific sequence composed of a regular character and combining marks that follow it, produce the alternation that will match all canonical equivalences of that sequence. |
private String[] |
producePermutations(String input)
Returns an array of strings that have all the possible permutations of the characters in the input string. |
private Pattern.Node |
range(Pattern.BitClass bits)
Parse a single character or a character range in a character class and return its representative node. |
private int |
read()
Read the next character, and advance the cursor by one. |
private int |
readEscaped()
Read the next character, and advance the cursor by one, ignoring the COMMENTS setting |
private void |
readObject(ObjectInputStream s)
Recompile the Pattern instance from a stream. |
private Pattern.Node |
ref(int refNum)
Parses a backref greedily, taking as many numbers as it can. |
private Pattern.Node |
retrieveCategoryNode(String name)
|
private Pattern.Node |
retrieveFamilyNode(String name)
|
private Pattern.Node |
sequence(Pattern.Node end)
Parsing of sequences between alternations. |
private int |
single()
|
private int |
skip()
Read the character after the next one, and advance the cursor by two. |
String[] |
split(CharSequence input)
Splits the given input sequence around matches of this pattern. |
String[] |
split(CharSequence input,
int limit)
Splits the given input sequence around matches of this pattern. |
private void |
subFlag()
Parses the second part of inlined match flags and turns off flags appropriately. |
private int |
u()
Utility method for parsing unicode escape sequences. |
private void |
unread()
Unread one next character, and retreat cursor by one. |
private int |
x()
Utility method for parsing hexadecimal escape sequences. |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
public static final int UNIX_LINES
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).
public static final int CASE_INSENSITIVE
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 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.
public static final int COMMENTS
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).
public static final int MULTILINE
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).
public static final int DOTALL
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.)
public static final int UNICODE_CASE
When this flag is specified then case-insensitive matching, when
enabled by the 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.
public static final int CANON_EQ
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 "å" 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.
private static final long serialVersionUID
private String pattern
private int flags
private transient String normalizedPattern
transient Pattern.Node root
transient Pattern.Node matchRoot
transient char[] buffer
transient Pattern.GroupHead[] groupNodes
private transient char[] temp
transient int groupCount
transient int localCount
private transient int cursor
private transient int patternLength
static final int MAX_REPS
static final int GREEDY
static final int LAZY
static final int POSSESSIVE
static final int INDEPENDENT
static Pattern.Node accept
static Pattern.Node lastAccept
static HashMap families
static HashMap categories
private static final String[] familyNames
private static final String[] categoryNames
private static final Pattern.Node[] familyNodes
private static final Pattern.Node[] categoryNodes
| Constructor Detail |
private Pattern(String p,
int f)
| Method Detail |
public static Pattern compile(String regex)
regex - The expression to be compiled
PatternSyntaxException - If the expression's syntax is invalid
public static Pattern compile(String regex,
int flags)
regex - The expression to be compiledflags - Match flags, a bit mask that may include
CASE_INSENSITIVE, MULTILINE, DOTALL,
UNICODE_CASE, and CANON_EQ
IllegalArgumentException - If bit values other than those corresponding to the defined
match flags are set in flags
PatternSyntaxException - If the expression's syntax is invalidpublic String pattern()
public Matcher matcher(CharSequence input)
input - The character sequence to be matched
public int flags()
public static boolean matches(String regex,
CharSequence input)
An invocation of this convenience method of the form
behaves in exactly the same way as the expressionPattern.matches(regex, input);
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.
regex - The expression to be compiledinput - The character sequence to be matched
PatternSyntaxException - If the expression's syntax is invalid
public String[] split(CharSequence input,
int limit)
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.
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" }
input - The character sequence to be splitlimit - The result threshold, as described above
public String[] split(CharSequence input)
This method works as if by invoking the two-argument split 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" }
input - The character sequence to be split
private void readObject(ObjectInputStream s)
throws IOException,
ClassNotFoundException
IOException
ClassNotFoundExceptionprivate void normalize()
private int normalizeCharClass(StringBuffer newPattern,
int i)
private String produceEquivalentAlternation(String source)
private String[] producePermutations(String input)
private int getClass(char c)
private String composeOneStep(String input)
private void compile()
private static void printObjectTree(Pattern.Node node)
private boolean has(int f)
private void accept(int ch,
String s)
private void mark(char c)
private int peek()
private int read()
private int readEscaped()
private int next()
private int nextEscaped()
private int peekPastWhitespace(int ch)
private int parsePastWhitespace(int ch)
private int parsePastLine()
private int peekPastLine()
private boolean isLineSeparator(int ch)
private int skip()
private void unread()
private Pattern.Node error(String s)
private Pattern.Node expr(Pattern.Node end)
private Pattern.Node sequence(Pattern.Node end)
private Pattern.Node atom()
private void append(int ch,
int len)
private Pattern.Node ref(int refNum)
private int escape(boolean inclass,
boolean create)
private Pattern.Node clazz(boolean consume)
private Pattern.Node range(Pattern.BitClass bits)
private int single()
private Pattern.Node family(boolean not,
boolean singleLetter)
private Pattern.Node retrieveFamilyNode(String name)
private Pattern.Node retrieveCategoryNode(String name)
private Pattern.Node familyError(String name,
String type)
private Pattern.Node group0()
private Pattern.Node createGroup(boolean anonymous)
private void addFlag()
private void subFlag()
private Pattern.Node closure(Pattern.Node prev)
private int c()
private int o()
private int x()
private int u()
private Pattern.Node newSingle(int ch)
private Pattern.Node newSlice(char[] buf,
int count)
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