core java volume 1:c The character c \unnnn, \xnn, \0n, \0nn, \0nnn The code unit with the given hex or octal value \t, \n, \r, \f, \a, \e The control characters tab, newline, return, form feed, alert, and escape \cc The control character corresponding to the character c Character Classes [C1C2. . .] Any of the characters represented by C1, C2, . . . The Ci are characters, character ranges (c1-c2), or character classes [^. . .] Complement of character class [ . . . && . . .] Intersection of two character classes Predefined Character Classes . Any character except line terminators (or any character if the DOTALL flag is set) \d A digit [0-9] \D A nondigit [^0-9] \s A whitespace character [ \t\n\r\f\x0B] \S A non-whitespace character \w A word character [a-zA-Z0-9_] \W A nonword character \p{name} A named character class—see Table 12-9 \P{name} The complement of a named character class Boundary Matchers ^ $ Beginning, end of input (or beginning, end of line in multiline mode) \b A word boundary \B A nonword boundary Syntax Explanation \A Beginning of input \z End of input \Z End of input except final line terminator \G End of previous match Quantifiers X? Optional X X* X, 0 or more times X+ X, 1 or more times X{n} X{n,} X{n,m} X n times, at least n times, between n and m times Quantifier Suffixes ? Turn default (greedy) match into reluctant match + Turn default (greedy) match into possessive match Set Operations XY Any string from X, followed by any string from Y X|Y Any string from X or Y Grouping (X) Capture the string matching X as a group \n The match of the nth group Escapes \c The character c (must not be an alphabetic character) \Q . . . \E Quote . . . verbatim (? . . . ) Special construct—see API notes of Pattern class
，终究还是会从指缝中一滴一滴流淌干净。
