return Ordering.from(forward).reverse();
    }

    @Override
    @ParametricNullness
    public K firstKey() {
      return forward().lastKey();
    }

    @Override
    @ParametricNullness
    public K lastKey() {
      return forward().firstKey();
    }

    @Override
    @CheckForNull

   * of {@code iterator2}.
   *
   * <p>Note that this will modify the supplied iterators, since they will have been advanced some
   * number of elements forward.
   */
  public static boolean elementsEqual(Iterator<?> iterator1, Iterator<?> iterator2) {
    while (iterator1.hasNext()) {
      if (!iterator2.hasNext()) {
        return false;
      }

    private final NavigableSet<E> forward;

    DescendingSet(NavigableSet<E> forward) {
      this.forward = forward;
    }

    @Override
    protected NavigableSet<E> delegate() {
      return forward;
    }

    @Override
    @CheckForNull
    public E lower(@ParametricNullness E e) {
      return forward.higher(e);
    }

    @Override