. Â Â the period is a wildcard for any character (letter, number, symbol, etc.).
[] Â Â square brackets are used in character classes.
() Â Â parenthesis are used in capturing groups.
{} Â Â curly brackets are used in quantifiers.
\ Â Â the backslash is used to precede a metacharacter or a predefined character class. It is also used to indicate a Java escape sequence character.
^ Â Â the caret is used for negation or the beginning of a line.
- Â Â the dash is used for ranges.
& Â Â the ampersand is used for intersections.
= Â Â the equals is used for special construct lookahead.
$ Â Â the dollar sign is a boundary matcher for the end of a line.
! Â Â the exclamation mark is used for special construct lookbehind.
| Â Â the pipe is used for or expressions.
? Â Â the question mark is used in quantifiers and special constructs.
* Â Â the asterisk is used in quantifiers.
+ Â Â the plus is used in quantifiers.
, Â Â the comma is used in quantifiers.