Summary of regex constructs.
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 |
\x{h…h} |
The character with hexadecimal value 0xh…h (Character.MIN_CODE_POINT ⇐ 0xh…h ⇐ Character.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') |
\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
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}\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] |
Classes for Unicode
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 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 |
\k<name> |
Whatever the named-capturing group “name” 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
Special constructs (named-capturing and non-capturing)
(?<name>X) |
X, as a named-capturing group |
(?:X) |
X, as a non-capturing group |
(?idmsuxU-idmsuxU) |
Nothing, but turns match flags i d m s u x U on – off |
(?idmsux-idmsux:X) |
X, as a non-capturing group with the given flags i d m s u x 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 |