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Regular expression summary

JavaFAQ Home » Text processing Go to all tips in Text processing

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[This text is taken directly from the Java API documentation]

Construct Matches
x The character x
\ The backslash character
n The character with octal value 0n (0 <= n <= 7)
nn The character with octal value 0nn (0 <= n <= 7)
mnn 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
The tab character ('\u0009')
The newline (line feed) character ('\u000A')
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: [ x0Bf ]
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: [ ]
p{Cntrl} A control character: [x00-x1Fx7F]
p{XDigit} A hexadecimal digit: [0-9a-fA-F]
p{Space} A whitespace character: [ x0Bf ]
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
 A word boundary
B A non-word boundary
A The beginning of the input
G The end of the previous match
 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
Grouping operators
(X) X. This capturing group is remembered so it can be referenced later. Numbered starting at 1.
(?:X) X. Used purely for grouping, and isn't remembered.
Back references
n Whatever the nth capturing group matched
Nothing, but quotes the following character
Q Nothing, but quotes all characters until E
E Nothing, but ends quoting started by Q
Special constructs (all groupings are non-capturing)
(?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

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