public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
            if (action == null) throw new NullPointerException();
            Node<K,V> p;
            if ((p = advance()) == null)
                return false;
            action.accept(new MapEntry<K,V>(p.key, p.val, map));
            return true;
        }
public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action)