Java Regular Expression

Regular expression grouping			Precautions
Capturing groups and non-capturing groups ( group numbering with left parenthesis in order )	(exp)	Match exp, and capture text into an automatically named group	Group name starts at 1 and increments (0 is the entire regular expression)
	(? <name>exp)	Match exp, and capture the text to a group named name, or you can write (? ') Name ' exp ')	The reverse reference method is: \name, \1
	(?: EXP)	Matches exp, does not capture matching text, and does not assign group numbers to this group
Greedy sub-expression	(? >exp)	Non-capturing group, but greedy match is performed on exp
0 width Positive lookahead assertion	(? =exp)	The assertion itself appears after the position can match the expression exp	The group must be a string of the maximum length determination That cannot appear \s*, \d+, etc.
0 width is recalling post assertion	(? <=exp)	The assertion itself appears before the position can match an expression exp
0 width Negative Predictive antecedent assertion	(?! Exp	Asserts that this position cannot be followed by an expression exp
0 width Negative Review post assertion	(? <!exp)	Assert that the front of this position cannot match an expression exp
Comments	(? #comment)

Regular expression pattern			Note
Unix_lines	(? d)	When matching ^ and $ in multiline mode, only \ n is set to recognize line terminator	Line Terminator 1
Case_insensitive	(? i)	Ignore case when matching characters	By default, only us ASCII characters are considered
COMMENTS	(? x)	Annotation mode 1. Non-escaped whitespace in the regular expression pattern is ignored 2. The number sign (#) is interpreted as the beginning of the comment, not the literal character. All text in the regular expression pattern, from the # character to the end of the line, is interpreted as a comment.	The whitespace of the word characters is interpreted verbatim, regardless of the use of the comments option. For example, the regular expression pattern [.,;:] matches any single empty characters, period, comma, semicolon, or colon.
MULTILINE	(? m)	^ and $ only match the beginning and end of the line, not the beginning and end of the entire input
LITERAL	No	Character mode (metacharacters and escape characters in the input are invalidated)
Dotall (single line)	(? s)	When using this flag, '. ' Symbol matches all characters, including line Terminator
Unicode_case	(? u)	When combined with case_insensitive, use Unicode letter case to match
Canon_eq	No	Consider the equivalence of Unicode character specifications

Java Regular Expression