docs: private static void checkPreconditions(final String regex, final String replacement) {
  		if( regex == null ) {
  			throw new NullPointerException("regex should not be null");
  		} else if( regex.length() == 0 ) {
  			throw new IllegalArgumentException("regex should not be empty");
  		}
  		
  		if( replacement == null ) {
  			throw new NullPointerException("replacement should not be null");
  		}
  	}