正则表达式matcher.group用法

group是针对（）来说的，group（0）指的整个串，group(1) 指的是第一个括号里的东西，group(2)指第二个括号里的东西。

@Test
    public void test01() {
        String regex = "(你*.?啊)|(AAA.*?BBB)|(CCC.*?DDD)";
        Pattern pattern = Pattern.compile(regex);
        String input = "你好啊|AAA123456内容2BcBB|CCC内容3DDD|CCC内容3DDD";

        Matcher matcher = pattern.matcher(input);
        log.info("匹配子模式数量： {}",matcher.groupCount());
        // find() 像迭代器那样向前遍历输入字符串
        while (matcher.find()) {
//            log.info("匹配项：{}",matcher.pattern().toString());
            /*group（0）就是指的整个串，group（1） 指的是第一个括号里的东西，group（2）指的第二个括*/
            log.info("??????????????????????????????????????????????");
            log.info("grou0 整串-> {}，start -> {} ,end -> {}",matcher.group(0),matcher.start(0),matcher.end(0));
            log.info("grou1 -> {}，start -> {} ,end -> {}",matcher.group(1),matcher.start(1),matcher.end(1));
            log.info("grou2 -> {}，start -> {} ,end -> {}",matcher.group(2),matcher.start(2),matcher.end(2));
            log.info("grou3 -> {}，start -> {} ,end -> {}",matcher.group(3),matcher.start(3),matcher.end(3));
       }
    }

输出结果：

[21:39:24:629] [INFO] - (test001.java:19) - 匹配子模式数量： 3
[21:39:24:633] [INFO] - (test001.java:24) - ??????????????????????????????????????????????
[21:39:24:633] [INFO] - (test001.java:25) - grou0 整串-> 你好啊，start -> 0 ,end -> 3
[21:39:24:633] [INFO] - (test001.java:26) - grou1 -> 你好啊，start -> 0 ,end -> 3
[21:39:24:633] [INFO] - (test001.java:27) - grou2 -> null，start -> -1 ,end -> -1
[21:39:24:634] [INFO] - (test001.java:28) - grou3 -> null，start -> -1 ,end -> -1
[21:39:24:634] [INFO] - (test001.java:24) - ??????????????????????????????????????????????
[21:39:24:634] [INFO] - (test001.java:25) - grou0 整串-> CCC内容3DDD，start -> 21 ,end -> 30
[21:39:24:634] [INFO] - (test001.java:26) - grou1 -> null，start -> -1 ,end -> -1
[21:39:24:634] [INFO] - (test001.java:27) - grou2 -> null，start -> -1 ,end -> -1
[21:39:24:634] [INFO] - (test001.java:28) - grou3 -> CCC内容3DDD，start -> 21 ,end -> 30
[21:39:24:635] [INFO] - (test001.java:24) - ??????????????????????????????????????????????
[21:39:24:635] [INFO] - (test001.java:25) - grou0 整串-> CCC内容3DDD，start -> 31 ,end -> 40
[21:39:24:635] [INFO] - (test001.java:26) - grou1 -> null，start -> -1 ,end -> -1
[21:39:24:635] [INFO] - (test001.java:27) - grou2 -> null，start -> -1 ,end -> -1
[21:39:24:635] [INFO] - (test001.java:28) - grou3 -> CCC内容3DDD，start -> 31 ,end -> 40

Process finished with exit code 0

可以看出，grou0 是匹配整个串，与grou() 结果相同。上面待匹配字符串中，能被 (你*.?啊)|(AAA.*?BBB)|(CCC.*?DDD) 匹配的字符串有你好啊、CCC内容3DDD、CCC内容3DDD，所以循环了3次，对应匹配的正则是

(你*.?啊)、(CCC.*?DDD)，位置刚好是对应的 grou0、grou3。

参考文章：

https://blog.csdn.net/u011289652/article/details/74474806

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