Java Regex捕获组

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class Tester {

   public static void main(String[] args) {

      //2 followed by 2 five times

      String test = "222222";

      String pattern = "(\\d\\d\\d\\d\\d)";

      Pattern r = Pattern.compile(pattern);

      Matcher m = r.matcher(test);

      if (m.find( )) {

         System.out.println("Matched!");

      }else {

         System.out.println("not matched!");

      }

      //\1 as back reference to capturing group (\d)

      pattern = "(\\d)\\1{5}";

      r = Pattern.compile(pattern);

      m = r.matcher(test);

      if (m.find( )) {

         System.out.println("Matched!");

      }else {

         System.out.println("not matched!");

      }

   }

}