public static String incrementAtIndex(final String s,final int index){
  final char[] chars=s.toCharArray();
  chars[index]=(char)(chars[index] + 1);
  return new String(chars);
}

public static String incrementAtIndex ( final String s , final int index ) { final char [ ] chars = s . toCharArray ( ) ; chars [ index ] = ( char ) ( chars [ index ] + 1 ) ; return new String ( chars ) ; }
increments a single character in the specified string .
