* 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
@ElementTypesAreNonnullByDefault
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
@ElementTypesAreNonnullByDefault
public abstract class ForwardingCollection<E extends @Nullable Object> extends ForwardingObject

import junit.framework.TestCase;
import junit.framework.TestSuite;

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

import junit.framework.TestCase;
import junit.framework.TestSuite;

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

 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
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

 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
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

 *
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
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();

 *
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
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();

 * We provide implementations of collections that forward all method calls to a delegate collection
 * by default. Subclasses can override one or more methods to implement the decorator pattern. For
 * an example, see {@link ForwardingCollection}.
 *
 * <h2>Other</h2>
 *
 * <ul>
 *   <li>{@link EvictingQueue}
 *   <li>{@link Interner}, {@link Interners}
 *   <li>{@link MapMaker}
 *   <li>{@link MinMaxPriorityQueue}

        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() {