Back references example

Ilias TsagklisNovember 11th, 2012Last Updated: August 14th, 2013

0 74 1 minute read

In this example we shall show you how to use Matcher.replaceAll(String replacement) API method to replace every subsequence of an input sequence that matches a specified pattern with a given replacement string. To replace any subsequence of a given sequence with a given String one should perform the following steps:

Compile a String regular expression to a Pattern, using compile(String regex) API method of Pattern.
Use matcher(CharSequence input) API method of Pattern to create a Matcher that will match the given String input against this pattern.
Use replaceAll(String replacement) API method, with a given String parameter to replace all subsequences of the sequence that matches the pattern with the given String,

as described in the code snippet below.

package com.javacodegeeks.snippets.basics;

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

public class BackRferences {
  public static void main(String args[]) {
    String reg_exxp = "(\\w)(\\d)(\\w+)";

    Pattern p = Pattern.compile(reg_exxp);

    String cand = "X99 ";

    Matcher m = p.matcher(cand);

    String temp = m.replaceAll("$33");

    System.out.println("REPLACEMENT: " + temp);
    System.out.println("ORIGINAL: " + cand);
  }
}

Output: