*
 * @author Louis Wasserman
 * @since 12.0
 */
@GwtIncompatible
public abstract class ForwardingNavigableSet<E extends @Nullable Object>
    extends ForwardingSortedSet<E> implements NavigableSet<E> {

  /** Constructor for use by subclasses. */
  protected ForwardingNavigableSet() {}

  @Override
  protected abstract NavigableSet<E> delegate();

  @Override

 *
 * @author Louis Wasserman
 * @since 12.0
 */
@GwtIncompatible
public abstract class ForwardingNavigableSet<E extends @Nullable Object>
    extends ForwardingSortedSet<E> implements NavigableSet<E> {

  /** Constructor for use by subclasses. */
  protected ForwardingNavigableSet() {}

  @Override
  protected abstract NavigableSet<E> delegate();

  @Override

    } else {
      return removeAllImpl(set, collection.iterator());
    }
  }

  @GwtIncompatible // NavigableSet
  static class DescendingSet<E extends @Nullable Object> extends ForwardingNavigableSet<E> {
    private final NavigableSet<E> forward;

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

    @Override
    protected NavigableSet<E> delegate() {