Reference http://www.cnblogs.com/KissKnife/archive/2008/03/23/1118423.html
(1) Basic syntax characters.
\ D 0-9 digits
The completion set of \ D (the complete set of all characters, the same below), that is, all non-numeric characters
\ W characters, which are uppercase/lowercase letters, 0-9 digits, and underscores
Set of \ W
\ S blank characters, including line breaks \ n, carriage returns \ r, tabs \ t, vertical tabs \ v, line breaks \ f
Set of \ s
. Any character except linefeed \ n
[…] Match All characters listed in []
[^…] Match characters not listed in []
String I = "\ n ";
String M = "3 ";
RegEx r = new RegEx (@ "\ D ");
// Same as RegEx r = new RegEx ("\ D ");
// R. ismatch (I) Result: True
// R. ismatch (m) Result: false
String I = "% ";
String M = "3 ";
RegEx r = new RegEx ("[a-z0-9]");
// Match lowercase letters or numbers
// R. ismatch (I) Result: false
// R. ismatch (m) Result: True