Collection<?> collection = (Collection<?>) elements;
        ensureRoomFor(collection.size());
        if (collection instanceof ImmutableCollection) {
          ImmutableCollection<?> immutableCollection = (ImmutableCollection<?>) collection;
          size = immutableCollection.copyIntoArray(contents, size);
          return this;
        }
      }
      super.addAll(elements);
      return this;
    }
  }

    }

    /**
     * Returns a newly-created {@code ImmutableCollection} of the appropriate type, containing the
     * elements provided to this builder.
     *
     * <p>Note that each builder class covariantly returns the appropriate type of {@code
     * ImmutableCollection} from this method.
     */
    public abstract ImmutableCollection<E> build();
  }

  @Override
  public ImmutableCollection<Entry<K, V>> entries() {
    return (ImmutableCollection<Entry<K, V>>) super.entries();
  }

  @Override
  ImmutableCollection<Entry<K, V>> createEntries() {
    return new EntryCollection<>(this);
  }

  private static final class EntryCollection<K, V> extends ImmutableCollection<Entry<K, V>> {
    @Weak final ImmutableMultimap<K, V> multimap;

   */
  @LazyInit
  private @Nullable ImmutableCollection<? extends ListenableFuture<? extends InputT>> futures;

  private final boolean allMustSucceed;
  private final boolean collectsValues;

  AggregateFuture(
      ImmutableCollection<? extends ListenableFuture<? extends InputT>> futures,
      boolean allMustSucceed,
      boolean collectsValues) {

    if (elements instanceof ImmutableCollection) {
      /*
       * TODO: When given an ImmutableList that's a sublist, copy the referenced
       * portion of the array into a new array to save space?
       */
      @SuppressWarnings("unchecked") // all supported methods are covariant
      ImmutableCollection<E> list = (ImmutableCollection<E>) elements;
      return list.asList();
    }

   */
  public static <E> ImmutableList<E> copyOf(Collection<? extends E> elements) {
    if (elements instanceof ImmutableCollection) {
      @SuppressWarnings("unchecked") // all supported methods are covariant
      ImmutableList<E> list = ((ImmutableCollection<E>) elements).asList();
      return list.isPartialView() ? ImmutableList.<E>asImmutableList(list.toArray()) : list;
    }

  final UnmodifiableIterator<Cell<R, C, V>> cellIterator() {
    throw new AssertionError("should never be called");
  }

  @Override
  public ImmutableCollection<V> values() {
    return (ImmutableCollection<V>) super.values();
  }

  @Override
  abstract ImmutableCollection<V> createValues();

  @Override
  final Iterator<V> valuesIterator() {
    throw new AssertionError("should never be called");
  }

      }
    };
  }

  @LazyInit @RetainedWith private transient @Nullable ImmutableCollection<V> values;

  /**
   * Returns an immutable collection of the values in this map, in the same order that they appear
   * in {@link #entrySet}.
   */
  @Override
  public ImmutableCollection<V> values() {
    ImmutableCollection<V> result = values;
    return (result == null) ? values = createValues() : result;
  }

  }

  @LazyInit @RetainedWith private transient @Nullable ImmutableCollection<V> values;

  /**
   * Returns an immutable collection of the values in this map, in the same order that they appear
   * in {@link #entrySet}.
   */
  @Override
  public ImmutableCollection<V> values() {
    ImmutableCollection<V> result = values;
    return (result == null) ? values = createValues() : result;
  }

 * {@link ImmutableCollection}.
 *
 * @since 2.0
 */
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableSet<E> extends ImmutableCollection<E> implements Set<E> {
  static final int SPLITERATOR_CHARACTERISTICS =
      ImmutableCollection.SPLITERATOR_CHARACTERISTICS | Spliterator.DISTINCT;

  /**