Basic Grammar

捕获组及反相引用 Grouping and Backreferences

• (regex): 捕获组. 如(abc){3}\1中,有一个捕获组(abc),后面复用该捕获组3次,之后反向引用捕获组1
• (?:regex): 非捕获组. 如(?:abc){3}中,有一个捕获组(abc),后面复用该捕获组3次,但无法反向引用捕获组
• (?<name>regex) 命名捕获组，Java7支持

修改器 Modifiers

• (?i)regex (?-i): 打开和关闭大小写敏感
• (?s)regex (?-s): 打开和关闭”dot matches newline”
• (?m)regex: ^ 匹配每行的开头 $ 匹配每行的结尾
• (?-m)regex: ^ 匹配全部内容的开头 $ 匹配全部内容的结尾
• (?i-sm)regex: 组合几个开关
• (?i-sm:reg1)reg2: 组合开关，只作用于reg1

Atomic Grouping and Possessive Quantifiers

• (?>regex)
• ?+, *+...

查看器 Lookaround

• (?=regex): Zero-width positive lookahead.
  • Zero-width: not consume any data, 1(?=2)3永远匹配失败
  • positive: ‘等于’
  • lookahead: ‘向前匹配’, ‘streets’–>t(?=s)–>第二个’t’
• (?!regex): Zero-width negative lookahead.
  • negative: ‘不等于’
• (?<=regex): Zero-width positive lookbehind.
  • lookbehind: ‘向后匹配’, ‘streets’–>(?<=s)t–>第一个’t’
• (?<!regex): Zero-width positive lookbehind.
  • negative: ‘不等于’

Continuing from The Previous Match

• \\Gregex

Conditionals

Comments

• (?#comment): comments

Common Usage

1. 匹配中文 [\u4e00-\u9fa5]

2. 匹配首尾空白字符 ^\s*|\s*$

3. 匹配邮件地址 \w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*

4. 匹配不含有连续横杠的字符串 (-(?!-)|[a-z0-9])*