}

    @Override
    public @Nullable T ceiling(T e) {
      return standardCeiling(e);
    }

    @Override
    public @Nullable T higher(T e) {
      return standardHigher(e);
    }

    @Override
    public @Nullable T pollFirst() {
      return standardPollFirst();
    }

    @Override
    public @Nullable T pollLast() {
      return standardPollLast();

   * #tailSet(Object, boolean)}. If you override {@link #tailSet(Object, boolean)}, you may wish to
   * override {@link #higher} to forward to this implementation.
   */
  @CheckForNull
  protected E standardHigher(@ParametricNullness E e) {
    return Iterators.getNext(tailSet(e, false).iterator(), null);
  }

  @Override
  @CheckForNull
  public E pollFirst() {
    return delegate().pollFirst();
  }