@Override
      public E get(int index) {
        return IndexedImmutableSet.this.get(index);
      }

      @Override
      boolean isPartialView() {
        return IndexedImmutableSet.this.isPartialView();
      }

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

      @Override
      ImmutableCollection<E> delegateCollection() {

 * for serialization to work.
 *
 * @author Louis Wasserman
 */
@GwtCompatible(serializable = true)
@ElementTypesAreNonnullByDefault
final class JdkBackedImmutableSet<E> extends IndexedImmutableSet<E> {
  private final Set<?> delegate;
  private final ImmutableList<E> delegateList;

  JdkBackedImmutableSet(Set<?> delegate, ImmutableList<E> delegateList) {
    this.delegate = delegate;

 *
 * @author Jesse Wilson
 * @author Kevin Bourrillion
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
final class ImmutableMapKeySet<K, V> extends IndexedImmutableSet<K> {
  private final ImmutableMap<K, V> map;

  ImmutableMapKeySet(ImmutableMap<K, V> map) {
    this.map = map;
  }

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

  @Override

  public ImmutableSet<E> elementSet() {
    ImmutableSet<E> result = elementSet;
    return (result == null) ? elementSet = new ElementSet() : result;
  }

  @WeakOuter
  private final class ElementSet extends IndexedImmutableSet<E> {

    @Override
    E get(int index) {
      return contents.getKey(index);
    }

    @Override
    public boolean contains(@CheckForNull Object object) {

  @Override
  final ImmutableSet<Cell<R, C, V>> createCellSet() {
    return isEmpty() ? ImmutableSet.<Cell<R, C, V>>of() : new CellSet();
  }

  @WeakOuter
  private final class CellSet extends IndexedImmutableSet<Cell<R, C, V>> {
    @Override
    public int size() {
      return RegularImmutableTable.this.size();
    }

    @Override
    Cell<R, C, V> get(int index) {
      return getCell(index);
    }

  }

  @Override
  ImmutableSet<K> createKeySet() {
    return new KeySet<>(this);
  }

  @GwtCompatible(emulated = true)
  private static final class KeySet<K> extends IndexedImmutableSet<K> {
    private final RegularImmutableMap<K, ?> map;

    KeySet(RegularImmutableMap<K, ?> map) {
      this.map = map;
    }

    @Override
    K get(int index) {