Match Duplicate Words : Pattern Match « Regular Expressions « Java Tutorial

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

public class Main {
  public static void main(String args[]) throws Exception {
    String duplicatePattern = "\\b(\\w+) \\1\\b";
    Pattern p = Pattern.compile(duplicatePattern);
    int matches = 0;
    String phrase = "this is a test";
    Matcher m = p.matcher(phrase);
    String val = null;
    while (m.find()) {
      val = ":" + + ":";

8.6.Pattern Match
8.6.1.Pattern.matches method
8.6.2.Find the end point of the second 'B(ond)'
8.6.3.Match Duplicate Words
8.6.4.Validate email address
8.6.5.Matching Line Boundaries in a Regular Expression
8.6.6.Regex for IP v4 Address
8.6.7.Regex for IP v6 Address