pattern

• A compiled representation of a regular expression.
• A regular expression, specified as a string, must first be compiled into an instance of this class. The resulting pattern can then be used to create a Matcher object that can match arbitrary character sequences against the regular expression. All of the state involved in performing a match resides in the matcher, so many matchers can share the same pattern. 
• 一个正则表达式的编译代表。
• 一个正则表达式，指定为一个字符串，必须第一被编译为这个类的实例。这个产生的模式然后能够被使用去创建一个匹配器对象，然后可以匹配任意字符序列用正则表达式。
• 所有的状态包含在匹配里，存在一个匹配器。所以很多匹配器能够分享同样的模式。
• Matcher(匹配器)
• An engine that performs match operations on a character sequence by interpreting a Pattern.

• A matcher is created from a pattern by invoking the pattern's matcher method. Once created, a matcher can be used to perform three different kinds of match operations: 

• 一个机器，在字符序列通过解析模式进行匹配操作。　　 performs match operations 进行匹配操作。
• 一个匹配器创建来自一个模式通过唤起模式的匹配器方法。第一次创建，这个匹配器能够被用在进行三个不同类型的匹配操作。
• group（1）方法
• Returns the input subsequence captured by the given group during the previous match operation.
• 通过一个给定的组返回一个捕获的输入子序列，在之前的匹配操作。