Regex backreferences in Java

Question

I had to match a number followed by itself 14 times. Then I\'ve came to the following regular expression in the regexstor.net/tester:

(\\d)\\1{14}
         


        

Answer 1

I think the main Problem is not the backreference - which works perfectly fine with \1 in java.

Your Problem is more likely the "overall" escaping of a regex pattern in Java.

If you want to have the pattern

(\d)\1{14}

passed to the regex engine, you first need to escape it cause it's a java-string when you write it:

(\\d)\\1{14}

Voila, works like a charm: goo.gl/BNCx7B (add http://, SO does not allow Url-Shorteners, but tutorialspoint.com has no other option as it seems)

Offline-Example:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class HelloWorld{

     public static void main(String []args){
        String test = "555555555555555"; // 5 followed by 5 for 14 times.

        String pattern = "(\\d)\\1{14}";

        Pattern r = Pattern.compile(pattern);
        Matcher m = r.matcher(test);
        if (m.find( )) {
           System.out.println("Matched!");   
        }else{
           System.out.println("not matched :-(");    
        }
     }
}