/**
 * Serializes execution of tasks, somewhat like an "asynchronous {@code synchronized} block." Each
 * {@linkplain #submit enqueued} callable will not be submitted to its associated executor until the
 * previous callable has returned -- and, if the previous callable was an {@link AsyncCallable}, not
 * until the {@code Future} it returned is {@linkplain Future#isDone done} (successful, failed, or
 * cancelled).
 *

    @Override
    public Integer next(Integer value) {
      return DELEGATE.next(value);
    }

    @Override
    public Integer previous(Integer value) {
      return DELEGATE.previous(value);
    }

    // Do *not* override offset() to delegate: We want to test the default implementation.

    @Override
    public long distance(Integer start, Integer end) {

   * That is, the first call to {@link #nextIndex()} will return {@code position}, and the first
   * call to {@link #next()} will return the element at that index, if available. Calls to {@link
   * #previous()} can retrieve the preceding {@code position} elements.
   *
   * @throws IndexOutOfBoundsException if {@code position} is negative or is greater than {@code
   *     size}

  }

  @Override
  public final boolean hasPrevious() {
    return backingIterator().hasPrevious();
  }

  @Override
  @ParametricNullness
  public final T previous() {
    return transform(backingIterator().previous());
  }

  @Override
  public final int nextIndex() {
    return backingIterator().nextIndex();
  }

  @Override
  public final int previousIndex() {

    @Override
    public Integer next(Integer value) {
      return DELEGATE.next(value);
    }

    @Override
    public Integer previous(Integer value) {
      return DELEGATE.previous(value);
    }

    // Do *not* override offset() to delegate: We want to test the default implementation.

    @Override
    public long distance(Integer start, Integer end) {

        @Override
        public Integer next(Integer value) {
          return integers().next(value);
        }

        @Override
        public Integer previous(Integer value) {
          return integers().previous(value);
        }

        @Override
        public long distance(Integer start, Integer end) {
          return integers().distance(start, end);
        }
      };

    assertEquals("4", iterator.previous());
    assertEquals("3", iterator.previous());
    assertEquals("2", iterator.previous());
    assertTrue(iterator.hasPrevious());
    assertEquals("1", iterator.previous());
    assertFalse(iterator.hasPrevious());
    assertEquals(-1, iterator.previousIndex());
    try {
      iterator.previous();
      fail("did not detect beginning of list");

    final AtomicBoolean setUpRan = new AtomicBoolean();
    Runnable setUp =
        new Runnable() {
          @Override
          public void run() {
            assertFalse("previous tearDown should have run before setUp", setUpRan.getAndSet(true));
          }
        };
    Runnable tearDown =
        new Runnable() {
          @Override
          public void run() {

    setSucceeds(lastEntry, entryIndex);
    setSucceeds(entryIndex, ENDPOINT);
  }

  @Override
  void accessEntry(int index) {
    if (accessOrder) {
      // delete from previous position...
      setSucceeds(getPredecessor(index), getSuccessor(index));
      // ...and insert at the end.
      setSucceeds(lastEntry, index);
      setSucceeds(index, ENDPOINT);
      incrementModCount();

    Map<K, V> delegate = Maps.newLinkedHashMap();
    for (Entry<? extends K, ? extends V> entry : entries) {
      K key = checkNotNull(entry.getKey());
      V previous = delegate.put(key, checkNotNull(entry.getValue()));
      if (throwIfDuplicateKeys && previous != null) {
        throw new IllegalArgumentException("duplicate key: " + key);
      }
    }
    this.delegate = Collections.unmodifiableMap(delegate);
  }