正则表达式之Pattern

java使用正则表达式的方式一般有两种：
1.直接利用String调用：

• string.matches(regex);//匹配
• string.replaceFirst(regex, replacement);//替换
• string.replaceAll(regex, replacement);
• string.replace(target,replacement);
  replace和replaceAll的区别
  2.使用Pattern+Matcher
  基本使用方法：

 Pattern p = Pattern.compile("a*b");
 Matcher m = p.matcher("aaaaab");
 boolean b = m.matches();

Pattern 基本是用来编译正则表达式的，主要的查找、匹配、替换等操作是有Matcher的实例对象来完成的，Matcher 的只有方法可以参考下这篇文章：
http://blog.csdn.net/cclovett/article/details/12448843

其中，String底层的匹配和替换使用Pattern+Matcher实现的，indexOf是直接进行匹配查找。
以下是正则表达式的构件模式串常用的一些结构：

预定义字符：
\\ 反斜杠
\t 间隔 ('\u0009')
\n 换行 ('\u000A')
\r 回车 ('\u000D')
\d 数字 等价于[0-9]
\D 非数字 等价于[^0-9]
\s 空白符号 [\t\n\x0B\f\r]
\S 非空白符号 [^\t\n\x0B\f\r]
\w 单独字符 [a-zA-Z_0-9]
\W 非单独字符 [^a-zA-Z_0-9]
\f 换页符
\e Escape
\b 一个单词的边界
\B 一个非单词的边界
\G 前一个匹配的结束
\h A horizontal whitespace character: [ \t\xA0\u1680\u180e\u2000-\u200a\u202f\u205f\u3000] 
\H A non-horizontal whitespace character: [^\h] 
\v A vertical whitespace character: [\n\x0B\f\r\x85\u2028\u2029]  
\V A non-vertical whitespace character: [^\v] 
^为限制开头
^java     条件限制为以Java为开头字符
$为限制结尾 java$     条件限制为以java为结尾字符
.  条件限制除\n以外任意一个单独字符
java..     条件限制为java后除换行外任意两个字符


加入特定限制条件「[]」
[a-z]     条件限制在小写a to z范围中一个字符
[A-Z]     条件限制在大写A to Z范围中一个字符
[a-zA-Z] 条件限制在小写a to z或大写A to Z范围中一个字符
[0-9]     条件限制在小写0 to 9范围中一个字符
[0-9a-z] 条件限制在小写0 to 9或a to z范围中一个字符
[0-9[a-z]] 条件限制在小写0 to 9或a to z范围中一个字符(交集)

[]中加入^后加再次限制条件「[^]」
[^a-z]     条件限制在非小写a to z范围中一个字符
[^A-Z]     条件限制在非大写A to Z范围中一个字符
[^a-zA-Z] 条件限制在非小写a to z或大写A to Z范围中一个字符
[^0-9]     条件限制在非小写0 to 9范围中一个字符
[^0-9a-z] 条件限制在非小写0 to 9或a to z范围中一个字符
[^0-9[a-z]] 条件限制在非小写0 to 9或a to z范围中一个字符(交集)

[a-d[m-p]] a to d 或者 m to p，相当于[a-dm-p]  (并集)
[a-z&&[def]] d, e, or f (intersection) （交集）
[a-z&&[^bc]] a through z, except for b and c: [ad-z] (差集) 
[a-z&&[^m-p]] a through z, and not m through p: [a-lq-z](差集) 

POSIX 标准中定义的预定义字符
{注意,使用的时候：Pattern pattern = Pattern.compile("\\p{Digit}*");}
\p{Lower} A lower-case alphabetic character: [a-z] 
\p{Upper} An upper-case alphabetic character:[A-Z] 
\p{ASCII} All ASCII:[\x00-\x7F] 
\p{Alpha} An alphabetic character:[\p{Lower}\p{Upper}] 
\p{Digit} A decimal digit: [0-9] 
\p{Alnum} An alphanumeric character:[\p{Alpha}\p{Digit}] 
\p{Punct} Punctuation: 标点符号
\p{Graph} A visible character: [\p{Alnum}\p{Punct}] 
\p{Print} A printable character: [\p{Graph}\x20] 
\p{Blank} A space or a tab: [ \t] 
\p{Cntrl} A control character: [\x00-\x1F\x7F] 
\p{XDigit} A hexadecimal digit: [0-9a-fA-F] 
\p{Space} A whitespace character: [ \t\n\x0B\f\r] 

Java提供的一些预定义字符 
\p{javaLowerCase} Equivalent to java.lang.Character.isLowerCase() 
\p{javaUpperCase} Equivalent to java.lang.Character.isUpperCase() 
\p{javaWhitespace} Equivalent to java.lang.Character.isWhitespace() 
\p{javaMirrored} Equivalent to java.lang.Character.isMirrored() 

Classes for Unicode scripts, blocks, categories and binary properties 
\p{IsLatin} A Latin script character (script) 
\p{InGreek} A character in the Greek block (block) 
\p{Lu} An uppercase letter (category) 
\p{IsAlphabetic} An alphabetic character (binary property) 
\p{Sc} A currency symbol 
\P{InGreek} Any character except one in the Greek block (negation) 
[\p{L}&&[^\p{Lu}]] Any letter except an uppercase letter (subtraction) 

Boundary matchers 
\b A word boundary 
\B A non-word boundary 
\A The beginning of the input 
\G The end of the previous match 
\Z The end of the input but for the final terminator, if any 
\z The end of the input 

Linebreak matcher 
\R Any Unicode linebreak sequence, is equivalent to \u000D\u000A|[\u000A\u000B\u000C\u000D\u0085\u2028\u2029]  

(描述出现次数的字符)
X? X(代表某一模式单个字符、预定义字符、[]、()等), 出现0次或1次
X* X出现0次或多次
X+ X出现一次或多次
X{n} X出现n次 
X{n,} X出现至少n次
X{n,m} X出现至少n-m次 

Reluctant quantifiers 
X?? X, once or not at all 
X*? X, zero or more times 
X+? X, one or more times 
X{n}? X, exactly n times 
X{n,}? X, at least n times 
X{n,m}? X, at least n but not more than m times 

Possessive quantifiers 
X?+ X, once or not at all 
X*+ X, zero or more times 
X++ X, one or more times 
X{n}+ X, exactly n times 
X{n,}+ X, at least n times 
X{n,m}+ X, at least n but not more than m times 

以下没看懂

Back references 
\n Whatever the nth capturing group matched 
\k<name> Whatever the named-capturing group "name" matched 

Quotation 
\ Nothing, but quotes the following character 
\Q Nothing, but quotes all characters until \E 
\E Nothing, but ends quoting started by \Q 

Special constructs (named-capturing and non-capturing) 
(?<name>X) X, as a named-capturing group 
(?:X) X, as a non-capturing group 
(?idmsuxU-idmsuxU)  Nothing, but turns match flags i d m s u x U on - off 
(?idmsux-idmsux:X)   X, as a non-capturing group with the given flags i d m s u x on - off 
(?=X) X, via zero-width positive lookahead 
(?!X) X, via zero-width negative lookahead 
(?<=X) X, via zero-width positive lookbehind 
(?<!X) X, via zero-width negative lookbehind 
(?>X) X, as an independent, non-capturing group