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

  @CanIgnoreReturnValue
  @Override
  public int drainTo(Collection<? super E> c, int maxElements) {
    return delegate().drainTo(c, maxElements);
  }

  @CanIgnoreReturnValue
  @Override
  public int drainTo(Collection<? super E> c) {
    return delegate().drainTo(c);
  }

  @CanIgnoreReturnValue // TODO(kak): consider removing this

  }

  private final Map<Class<? extends @NonNull B>, B> delegate;

  private MutableClassToInstanceMap(Map<Class<? extends @NonNull B>, B> delegate) {
    this.delegate = checkNotNull(delegate);
  }

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

  /**

  }

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

  @Override
  public final State state() {
    return delegate.state();
  }

  /**
   * @since 13.0
   */
  @Override
  public final void addListener(Listener listener, Executor executor) {
    delegate.addListener(listener, executor);
  }

  /**
   * @since 14.0
   */

  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);
  }

  @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() {

    private final Callable<T> delegate;

    WrappedCallable(Callable<T> delegate) {
      this.delegate = delegate;
    }

    @Override
    public T call() throws Exception {
      return delegate.call();
    }
  }

  private static final class WrappedRunnable implements Runnable {
    private final Runnable delegate;

    WrappedRunnable(Runnable delegate) {
      this.delegate = delegate;
    }

  final transient Collection<E> delegate;

  ForwardingImmutableCollection(Collection<E> delegate) {
    this.delegate = delegate;
  }

  @Override
  public UnmodifiableIterator<E> iterator() {
    return Iterators.unmodifiableIterator(delegate.iterator());
  }

  @Override
  public boolean contains(@Nullable Object object) {
    return object != null && delegate.contains(object);
  }

  @Override

      boolean toInclusive) {
    return delegate().subMap(fromKey, fromInclusive, toKey, toInclusive);
  }

  @Override
  public NavigableMap<K, V> headMap(@ParametricNullness K toKey, boolean inclusive) {
    return delegate().headMap(toKey, inclusive);
  }

  @Override
  public NavigableMap<K, V> tailMap(@ParametricNullness K fromKey, boolean inclusive) {
    return delegate().tailMap(fromKey, inclusive);
  }

      boolean toInclusive) {
    return delegate().subMap(fromKey, fromInclusive, toKey, toInclusive);
  }

  @Override
  public NavigableMap<K, V> headMap(@ParametricNullness K toKey, boolean inclusive) {
    return delegate().headMap(toKey, inclusive);
  }

  @Override
  public NavigableMap<K, V> tailMap(@ParametricNullness K fromKey, boolean inclusive) {
    return delegate().tailMap(fromKey, inclusive);
  }

  }

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

  @Override
  public final State state() {
    return delegate.state();
  }

  /**
   * @since 13.0
   */
  @Override
  public final void addListener(Listener listener, Executor executor) {
    delegate.addListener(listener, executor);
  }

  /**
   * @since 14.0
   */