*
 * @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

import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;

/**
 * Tests for {@code ForwardingNavigableSet}.
 *
 * @author Louis Wasserman
 */
@NullUnmarked
public class ForwardingNavigableSetTest extends TestCase {
  static class StandardImplForwardingNavigableSet<T> extends ForwardingNavigableSet<T> {
    private final NavigableSet<T> backingSet;

 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
/*
 * We provide and encourage use of ForwardingNavigableSet over this class, but we still provide this
 * one to preserve compatibility.
 */
@SuppressWarnings("JdkObsolete")
public abstract class ForwardingSortedMap<K extends @Nullable Object, V extends @Nullable Object>

 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
/*
 * We provide and encourage use of ForwardingNavigableSet over this class, but we still provide this
 * one to preserve compatibility.
 */
@SuppressWarnings("JdkObsolete")
public abstract class ForwardingSortedSet<E extends @Nullable Object> extends ForwardingSet<E>

    } 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() {

      }
    };
  }

  @GwtIncompatible // NavigableSet
  private static <E extends @Nullable Object> NavigableSet<E> removeOnlyNavigableSet(
      NavigableSet<E> set) {
    return new ForwardingNavigableSet<E>() {
      @Override
      protected NavigableSet<E> delegate() {
        return set;
      }

      @Override
      public boolean add(@ParametricNullness E element) {

      }
    };
  }

  @GwtIncompatible // NavigableSet
  private static <E extends @Nullable Object> NavigableSet<E> removeOnlyNavigableSet(
      NavigableSet<E> set) {
    return new ForwardingNavigableSet<E>() {
      @Override
      protected NavigableSet<E> delegate() {
        return set;
      }

      @Override
      public boolean add(@ParametricNullness E element) {