docs: private void checkAndAddForbiddenStrings(final List<String> forbiddenSubStrings) {
  		for( String forbidden : forbiddenSubStrings ) {
  			if( forbidden == null ) {
  				throw new NullPointerException("forbidden substring should not be null");
  			}
  			this.forbiddenSubStrings.add(forbidden);
  		}
  	}