/**
 * An iterator that does not support {@link #remove}.
 *
 * <p>{@code UnmodifiableIterator} is used primarily in conjunction with implementations of {@link
 * ImmutableCollection}, such as {@link ImmutableList}. You can, however, convert an existing
 * iterator to an {@code UnmodifiableIterator} using {@link Iterators#unmodifiableIterator}.
 *
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible

  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

    return delegateList().equals(obj);
  }

  @Override
  public int hashCode() {
    return delegateList().hashCode();
  }

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

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

            children(t).forEach(this);
          }
        }.accept(root);
      }
    };
  }

  UnmodifiableIterator<T> preOrderIterator(T root) {
    return new PreOrderIterator(root);
  }

  private final class PreOrderIterator extends UnmodifiableIterator<T> {
    private final Deque<Iterator<T>> stack;

    PreOrderIterator(T root) {
      this.stack = new ArrayDeque<>();

  }

  // This declaration is needed to make Set.iterator() and
  // ImmutableCollection.iterator() appear consistent to javac's type inference.
  @Override
  public abstract UnmodifiableIterator<E> iterator();

  abstract static class CachingAsList<E> extends ImmutableSet<E> {
    @LazyInit private transient ImmutableList<E> asList;

    @Override
    public ImmutableList<E> asList() {

    return new FluentIterable<T>() {
      @Override
      public UnmodifiableIterator<T> iterator() {
        return preOrderIterator(root);
      }
    };
  }

  UnmodifiableIterator<T> preOrderIterator(T root) {
    return new PreOrderIterator(root);
  }

  private final class PreOrderIterator extends UnmodifiableIterator<T> {
    private final Deque<Iterator<T>> stack;

    IncidentEdgeSet<N> incident =
        new IncidentEdgeSet<N>(this, node) {
          @Override
          public UnmodifiableIterator<EndpointPair<N>> iterator() {
            if (graph.isDirected()) {
              return Iterators.unmodifiableIterator(
                  Iterators.concat(
                      Iterators.transform(
                          graph.predecessors(node).iterator(),

    return new AbstractSet<E>() {
      @Override
      public UnmodifiableIterator<E> iterator() {
        Iterable<E> incidentEdges =
            (selfLoopCount == 0)
                ? Iterables.concat(inEdgeMap.keySet(), outEdgeMap.keySet())
                : Sets.union(inEdgeMap.keySet(), outEdgeMap.keySet());
        return Iterators.unmodifiableIterator(incidentEdges.iterator());
      }

      @Override

  }

  final Set<K> unmodifiableKeySet() {
    return new AbstractSet<K>() {
      @Override
      public UnmodifiableIterator<K> iterator() {
        Iterator<Entry<K, V>> entryIterator = backingMap.entrySet().iterator();

        return new UnmodifiableIterator<K>() {
          @Override
          public boolean hasNext() {
            return entryIterator.hasNext();
          }

    this.map = map;
  }

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

  @Override
  public UnmodifiableIterator<V> iterator() {
    return new UnmodifiableIterator<V>() {
      final UnmodifiableIterator<Entry<K, V>> entryItr = map.entrySet().iterator();

      @Override
      public boolean hasNext() {
        return entryItr.hasNext();
      }

      @Override