code: public void add(Key[] keys){
      if(keys == null) {
        throw new IllegalArgumentException("Key[] may not be null");
      }
      for(int i = 0; i < keys.length; i++) {
        add(keys[i]);
      }
    }
docs: Adds an array of keys to <i>this</i> filter.
  @param keys The array of keys.