Regular Expression Syntax Reference
This section provides a brief summary of regexp syntax that can be helpful for creating search and issue navigation patterns.
RegEx syntax reference
| Character | Description |
|---|---|
\ | Marks the next character as either a special character or a literal. For example:
|
^ | Matches the beginning of input. |
$ | Matches the end of input. |
* | Matches the preceding character zero or more times. For example, "zo*" matches either z or zoo. |
+ | Matches the preceding character one or more times. For example, "zo+" matches zoo but not z. |
? | Matches the preceding character zero or one time. For example, a?ve? matches the ve in never. |
. | Matches any single character except a newline character. |
(subexpression) | Matches subexpression and remembers the match. If a part of a regular expression is enclosed in parentheses, that part of the regular expression is grouped together. Thus a regex operator can be applied to the entire group.
|
x |y | Matches either x or y. For example, z|wood matches z or wood. (z|w)oo matches zoo or wood. |
{n} | n is a nonnegative integer. Matches exactly n times. For example, o{2} does not match the o in Bob, but matches the first two o's in foooood. |
{n,} | n is a nonnegative integer. Matches at least n times. For example,
|
{ n , m } | m and n are nonnegative integers. Matches at least n and at most m times. For example, o{1,3} matches the first three o's in "fooooood." o{0,1} is equivalent to o?. |
[xyz] | A character set. Matches any one of the enclosed characters. For example, [abc] matches the a in plain. |
[^ xyz ] | A negative character set. Matches any character not enclosed. For example, [^abc] matches the p in plain. |
[ a-z ] | A range of characters. Matches any character in the specified range. For example, "[a-z]" matches any lowercase alphabetic character in the range a through z. |
[^ m-z ] | A negative range characters. Matches any character not in the specified range. For example, [^m-z] matches any character not in the range m through z. |
\b | Matches a word boundary, that is, the position between a word and a space. For example, er\b matches the er in never but not the er in verb. |
\B | Matches a non-word boundary. ea*r\B matches the ear in never early. |
\d | Matches a digit character. Equivalent to [0-9]. |
\D | Matches a non-digit character. Equivalent to [^0-9]. |
\f | Matches a form-feed character. |
\n | Matches a newline character. |
\r | Matches a carriage return character. |
\s | Matches any white space including space, tab, form-feed, etc. Equivalent to [ \f\n\r\t\v]. |
\S | Matches any nonwhite space character. Equivalent to [^ \f\n\r\t\v]. |
\t | Matches a tab character. |
\v | Matches a vertical tab character. |
\w | Matches any word character including underscore. Equivalent to [A-Za-z0-9_]. |
\W | Matches any non-word character. Equivalent to [^A-Za-z0-9_]. |
\num | Matches num, where num is a positive integer, denoting a reference back to remembered matches. For example, |
\n | Matches n, where n is an octal escape value. Octal escape values should be 1, 2, or 3 digits long. For example,
Octal escape values should not exceed 256. If they do, only the first two digits comprise the expression. Allows ASCII codes to be used in regular expressions. |
\xn | Matches n, where n is a hexadecimal escape value. Hexadecimal escape values must be exactly two digits long. For example, Allows ASCII codes to be used in regular expressions. |
\\$ | Escapes $. |
\l | Changes the case of the next character to the lower case. |
\u | Changes the case of the next character to the upper case. |
\L | Changes the case of all the subsequent characters up to \E to the lower case. |
\U | Changes the case of all the subsequent characters up to \E to the upper case. |
Tips and Tricks
IntelliJ IDEA provides intention actions to check validity of the regular expressions, and edit regular expressions in a scratchpad. Place the caret at a regular expression, and press Alt+Enter. The suggestion list of intention actions, available in this context, appears:
- Choose , and press Enter. The dialog box that pops up, shows the current regular expression in the upper pane. In the lower pane, type the string to which this expression should match. If the regular expression matches the entered string, the background becomes green. If the regular expression doesn't match, then the background is red.
- Choose , and press Enter. The regular expression opens for editing in a separate tab in the editor. However, this is but a scratchpad, and no file is physically created:
As you type in the scratchpad, all changes are synchronized with the original regular expression. Press Escape to close the editor tab.