基础: Pattern和Matcher

字符串处理离不开正则表达式，从jdk1.4开始，结合Pattern和Matcher即可实现正则处理，

下面列举一些利用java处理字符串的示例:

1. 判断字符串中是否包含index_xxx这样的数据(xxx只能是数字和字母)

部分匹配

Pattern pattern = Pattern.compile("index_\\w+");
Matcher matcher = pattern.matcher("100+index_a2bc1*200");
System.out.println(matcher.find());

全文匹配

Pattern pattern = Pattern.compile(".+index_\\w+.+");
Matcher matcher = pattern.matcher("100+index_a2bc1*200");
System.out.println(matcher.matches());     #true
System.out.println(Pattern.matches("index_\\w_", "100+index_a2bc1*200"));   #false

2.查询形式为:index_xxx的全部字符串(xxx只能是数字和字母)

Pattern pattern = Pattern.compile("index_\\w+");
Matcher matcher = pattern.matcher("100+index_a2bc1*200+index_aka21*(index_kab21-3023)");
while(matcher.find()) {
    System.out.println(matcher.group());
}

结果：

index_a2bc1
index_aka21
index_kab21

3.查询index_xxx后的xxx字符串

Pattern pattern = Pattern.compile("index_(\\w+)");
Matcher matcher = pattern.matcher("100+index_a2bc1*200+index_aka21*(index_kab21-3023)");
while(matcher.find()) {
    System.out.println(matcher.group());
}

结果：

a2bc1
aka21
kab21

5.分析以下日志，截取日期，用户，操作内容

2018-03-11 10:11:02.199 user:张三 operation:login 
2018-03-12 10:11:02.199 user:李四 operation:login 
2018-03-13 10:11:02.199 user:张三 operation:edit_info 
2018-03-14 10:11:02.199 user:张三 operation:exit

实现:

String data = "2018-03-11 10:11:02.199 user:张三 operation:login \n" +
        "2018-03-12 10:11:02.199 user:李四 operation:login \n" +
        "2018-03-13 10:11:02.199 user:张三 operation:edit_info \n" +
        "2018-03-14 10:11:02.199 user:张三 operation:exit";

Pattern pattern = Pattern.compile("(\\d{4}-\\d{2}-\\d{2}).* user:(.*) operation:(.*)");
Matcher matcher = pattern.matcher(data);
while(matcher.find()) {
    System.out.print(matcher.group(1)); #对应第一个分组
    System.out.print(matcher.group(2)); #对应第二个分组
    System.out.print(matcher.group(3)); #对应第三个分组
    System.out.println();
}

结果:

2018-03-11张三login 
2018-03-12李四login 
2018-03-13张三edit_info 
2018-03-14张三exit