* invoke methods, they invoke methods on the {@code ForwardingCollection}.
 *
 * <p>The {@code standard} methods are not guaranteed to be thread-safe, even when all of the
 * methods that they depend on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingCollection<E extends @Nullable Object> extends ForwardingObject

 * invoke methods, they invoke methods on the {@code ForwardingCollection}.
 *
 * <p>The {@code standard} methods are not guaranteed to be thread-safe, even when all of the
 * methods that they depend on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingCollection<E extends @Nullable Object> extends ForwardingObject

import org.jspecify.annotations.NullUnmarked;

/**
 * Tests for {@link ForwardingCollection}.
 *
 * @author Robert Konigsberg
 * @author Hayward Chan
 * @author Louis Wasserman
 */
@NullUnmarked
public class ForwardingCollectionTest extends TestCase {
  static final class StandardImplForwardingCollection<T> extends ForwardingCollection<T> {
    private final Collection<T> backingCollection;

 * methods that they depend on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingSet<E extends @Nullable Object> extends ForwardingCollection<E>
    implements Set<E> {
  // TODO(lowasser): identify places where thread safety is actually lost

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

  @Override

 * methods that they depend on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingSet<E extends @Nullable Object> extends ForwardingCollection<E>
    implements Set<E> {
  // TODO(lowasser): identify places where thread safety is actually lost

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

  @Override

 * methods that they depend on are thread-safe.
 *
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingQueue<E extends @Nullable Object> extends ForwardingCollection<E>
    implements Queue<E> {

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

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

 * methods that they depend on are thread-safe.
 *
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingQueue<E extends @Nullable Object> extends ForwardingCollection<E>
    implements Queue<E> {

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

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

        public boolean retainAll(Collection<?> c) {
          return delegate.keySet().retainAll(c);
        }
      };
    }

    @Override
    public Collection<V> values() {
      return new ForwardingCollection<V>() {
        @Override
        protected Collection<V> delegate() {
          return delegate.values();
        }

        @Override
        public Iterator<V> iterator() {

 *
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingList<E extends @Nullable Object> extends ForwardingCollection<E>
    implements List<E> {
  // TODO(lowasser): identify places where thread safety is actually lost

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

  @Override

 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingMultiset<E extends @Nullable Object> extends ForwardingCollection<E>
    implements Multiset<E> {

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

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

  @Override