Hi Sahil

The problem you shared with us is already have solution. Go through the code below :

http://www.roseindia.net/tutorial/jquery/jquerycheckusername.html

The code below used jQuery post method which check the username availability without changing the page.

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

public class UsernameValidator{

  private Pattern pattern;
  private Matcher matcher;

  private static final String USERNAME_PATTERN = "^[a-z0-9_-]{3,15}$";

  public UsernameValidator(){
      pattern = Pattern.compile(USERNAME_PATTERN);
  }

  public boolean validate(final String username){

      matcher = pattern.matcher(username);
      return matcher.matches();

  }

}