}

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

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

        @Override
        @ParametricNullness
        public T next() {
          if (!hasNext()) {
            throw new NoSuchElementException();
          }

    int indexToRemove = -1;

    @Override
    public boolean hasNext() {
      return currentIndex >= 0;
    }

    @ParametricNullness
    abstract T getOutput(int entry);

    @Override
    @ParametricNullness
    public T next() {
      checkForConcurrentModification();
      if (!hasNext()) {
        throw new NoSuchElementException();
      }

    return new UnmodifiableIterator<E>() {
      int remaining;
      @Nullable E element;

      @Override
      public boolean hasNext() {
        return (remaining > 0) || entryIterator.hasNext();
      }

      @Override
      public E next() {
        if (remaining <= 0) {
          Entry<E> entry = entryIterator.next();
          element = entry.getElement();

      return new Iterator<Entry<K, V>>() {
        private @Nullable Entry<K, V> toRemove = null;
        private @Nullable Entry<K, V> nextOrNull = forward().lastEntry();

        @Override
        public boolean hasNext() {
          return nextOrNull != null;
        }

        @Override
        public Entry<K, V> next() {
          if (nextOrNull == null) {
            throw new NoSuchElementException();
          }

      return new Iterator<Entry<K, V>>() {
        private @Nullable Entry<K, V> toRemove = null;
        private @Nullable Entry<K, V> nextOrNull = forward().lastEntry();

        @Override
        public boolean hasNext() {
          return nextOrNull != null;
        }

        @Override
        public Entry<K, V> next() {
          if (nextOrNull == null) {
            throw new NoSuchElementException();
          }

  UnmodifiableIterator<K> keyIterator() {
    UnmodifiableIterator<Entry<K, V>> entryIterator = entrySet().iterator();
    return new UnmodifiableIterator<K>() {
      @Override
      public boolean hasNext() {
        return entryIterator.hasNext();
      }

      @Override
      public K next() {
        return entryIterator.next().getKey();
      }
    };
  }

  @GwtIncompatible // Spliterator

    return new UnmodifiableIterator<E>() {
      int remaining;
      @Nullable E element;

      @Override
      public boolean hasNext() {
        return (remaining > 0) || entryIterator.hasNext();
      }

      @Override
      public E next() {
        if (remaining <= 0) {
          Entry<E> entry = entryIterator.next();
          element = entry.getElement();

    Itr(Object[] array) {
      lastRet = -1;
      this.array = array;
    }

    @CanIgnoreReturnValue // pushed down from class to method
    @Override
    public boolean hasNext() {
      return cursor < array.length;
    }

    @CanIgnoreReturnValue // pushed down from class to method
    @Override
    public E next() {

    assertTrue(consumingIterator.hasNext());
    assertThat(list).containsExactly("a", "b").inOrder();
    assertThat(consumingIterator.next()).isEqualTo("a");
    assertThat(list).contains("b");

    assertTrue(consumingIterator.hasNext());
    assertThat(consumingIterator.next()).isEqualTo("b");
    assertThat(list).isEmpty();

    assertFalse(consumingIterator.hasNext());
  }

  @GwtIncompatible // ?

    return () ->
        new Iterator<B>() {
          private final Iterator<? extends A> fromIterator = fromIterable.iterator();

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

          @Override
          public B next() {
            return convert(fromIterator.next());
          }

          @Override