*/
  @CanIgnoreReturnValue
  @Deprecated
  @GwtIncompatible // NavigableSet
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  @CheckForNull
  public final E pollFirst() {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the set unmodified.
   *
   * @since 12.0
   * @throws UnsupportedOperationException always

   */
  @CanIgnoreReturnValue
  @Deprecated
  @GwtIncompatible // NavigableSet
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  @CheckForNull
  public final E pollFirst() {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the set unmodified.
   *
   * @since 12.0
   * @throws UnsupportedOperationException always

    }

    @Override
    @CheckForNull
    public K higher(@ParametricNullness K e) {
      return map().higherKey(e);
    }

    @Override
    @CheckForNull
    public K pollFirst() {
      return keyOrNull(map().pollFirstEntry());
    }

    @Override
    @CheckForNull
    public K pollLast() {
      return keyOrNull(map().pollLastEntry());
    }

    @Override

    }

    @Override
    @CheckForNull
    public K higher(@ParametricNullness K e) {
      return map().higherKey(e);
    }

    @Override
    @CheckForNull
    public K pollFirst() {
      return keyOrNull(map().pollFirstEntry());
    }

    @Override
    @CheckForNull
    public K pollLast() {
      return keyOrNull(map().pollLastEntry());
    }

    @Override