java 正则表达式

    package cn.mingyuan.regexp.singlecharacter;  
      
    import java.util.regex.Matcher;  
    import java.util.regex.Pattern;  
      
    public class GroupIndexAndStartEndIndexTest {  
      
    /** 
    * @param args 
    */  
    public static void main(String[] args) {  
       // TODO Auto-generated method stub  
       String str = "Hello,World! in Java.";  
       Pattern pattern = Pattern.compile("W(or)(ld!)");  
       Matcher matcher = pattern.matcher(str);  
       while(matcher.find()){  
        System.out.println("Group 0:"+matcher.group(0));//得到第0组——整个匹配  
        System.out.println("Group 1:"+matcher.group(1));//得到第一组匹配——与(or)匹配的  
        System.out.println("Group 2:"+matcher.group(2));//得到第二组匹配——与(ld!)匹配的，组也就是子表达式  
        System.out.println("Start 0:"+matcher.start(0)+" End 0:"+matcher.end(0));//总匹配的索引  
        System.out.println("Start 1:"+matcher.start(1)+" End 1:"+matcher.end(1));//第一组匹配的索引  
        System.out.println("Start 2:"+matcher.start(2)+" End 2:"+matcher.end(2));//第二组匹配的索引  
        System.out.println(str.substring(matcher.start(0),matcher.end(1)));//从总匹配开始索引到第1组匹配的结束索引之间子串——Wor  
       }  
    }  
      
    }  

Group 0:World!  
Group 1:or  
Group 2:ld!  
Start 0:6 End 0:12  
Start 1:7 End 1:9  
Start 2:9 End 2:12  
Wor