@NullUnmarked
class LockHeldAssertingSet<E> extends ForwardingSet<E> implements Serializable {
  final Set<E> delegate;
  final Object mutex;

  LockHeldAssertingSet(Set<E> delegate, Object mutex) {
    checkNotNull(mutex);
    this.delegate = delegate;
    this.mutex = mutex;
  }

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

  @Override
  public String toString() {
    assertTrue(Thread.holdsLock(mutex));

    return delegate().get(index);
  }

  @Override
  public int indexOf(@Nullable Object element) {
    return delegate().indexOf(element);
  }

  @Override
  public int lastIndexOf(@Nullable Object element) {
    return delegate().lastIndexOf(element);
  }

  @Override
  public ListIterator<E> listIterator() {
    return delegate().listIterator();
  }

  @Override

    }
    Set<E> delegate = delegateOrNull();
    return (delegate != null)
        ? delegate.spliterator()
        : Spliterators.spliterator(
            requireElements(), 0, size, Spliterator.DISTINCT | Spliterator.ORDERED);
  }

  @Override
  public void forEach(Consumer<? super E> action) {
    checkNotNull(action);
    Set<E> delegate = delegateOrNull();
    if (delegate != null) {

  @Override
  protected abstract Map<K, V> delegate();

  @Override
  public int size() {
    return delegate().size();
  }

  @Override
  public boolean isEmpty() {
    return delegate().isEmpty();
  }

  @CanIgnoreReturnValue
  @Override
  public @Nullable V remove(@Nullable Object key) {
    return delegate().remove(key);
  }

  @Override
  public void clear() {

    return new Builder<B>().putAll(map).build();
  }

  private final ImmutableMap<Class<? extends B>, B> delegate;

  private ImmutableClassToInstanceMap(ImmutableMap<Class<? extends B>, B> delegate) {
    this.delegate = delegate;
  }

  @Override
  protected Map<Class<? extends B>, B> delegate() {
    return delegate;
  }

  @Override
  @SuppressWarnings("unchecked") // value could not get in if not a T

    @ParametricNullness final K key;
    Collection<V> delegate;
    final @Nullable WrappedCollection ancestor;
    final @Nullable Collection<V> ancestorDelegate;

    WrappedCollection(
        @ParametricNullness K key, Collection<V> delegate, @Nullable WrappedCollection ancestor) {
      this.key = key;
      this.delegate = delegate;
      this.ancestor = ancestor;

   * constructed {@link Future} as the delegate.
   *
   * @since 9.0
   */
  public abstract static class SimpleForwardingFuture<V extends @Nullable Object>
      extends ForwardingFuture<V> {
    private final Future<V> delegate;

    protected SimpleForwardingFuture(Future<V> delegate) {
      this.delegate = Preconditions.checkNotNull(delegate);
    }

    @Override

  static <E> ImmutableSet<E> asImmutable(Set<E> delegate) {
    switch (delegate.size()) {
      case 0:
        return ImmutableSet.of();
      case 1:
        return ImmutableSet.of(Iterables.getOnlyElement(delegate));
      default:
        return new ImmutableEnumSet<E>(delegate);
    }
  }

  public ImmutableEnumSet(Set<E> delegate) {
    super(delegate);
  }

    this.delegate = delegate;
    this.delegateList = delegateList;
  }

  RegularImmutableAsList(ImmutableCollection<E> delegate, Object[] array) {
    this(delegate, asImmutableList(array));
  }

  @Override
  ImmutableCollection<E> delegateCollection() {
    return delegate;
  }

  ImmutableList<? extends E> delegateList() {

        when(delegate.hasNext()).thenReturn(false);
        NetServerFileEntryAdapterIterator itr = new NetServerFileEntryAdapterIterator(parent, delegate, null);

        // Act
        itr.remove();

        // Assert
        verify(delegate, times(1)).remove();
    }

    @Test
    @DisplayName("Edge: empty delegate yields no elements")
    void emptyDelegate_hasNoNext() {