}

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

  @CanIgnoreReturnValue
  @Override
  @ParametricNullness
  public E previous() {
    return delegate().previous();
  }

  @Override
  public int previousIndex() {
    return delegate().previousIndex();
  }

  @Override
  public void set(@ParametricNullness E element) {

   * executor. The listener will have the corresponding transition method called whenever the
   * service changes state. The listener will not have previous state changes replayed, so it is
   * suggested that listeners are added before the service starts.
   *
   * <p>{@code addListener} guarantees execution ordering across calls to a given listener but not

  public void fetch(HttpUrl url) throws IOException {
    // Skip hosts that we've visited many times.
    AtomicInteger hostnameCount = new AtomicInteger();
    AtomicInteger previous = hostnames.putIfAbsent(url.host(), hostnameCount);
    if (previous != null) hostnameCount = previous;
    if (hostnameCount.getAndIncrement() >= hostLimit) return;

    Request request = new Request.Builder()
        .url(url)
        .build();

  }

  /**
   * Atomically sets the element at position {@code i} to the given value and returns the old value.
   *
   * @param i the index
   * @param newValue the new value
   * @return the previous value
   */
  public final double getAndSet(int i, double newValue) {
    long next = doubleToRawLongBits(newValue);
    return longBitsToDouble(longs.getAndSet(i, next));
  }

  /**

    /**
     * The elements to be returned by future calls to {@code previous()}, with the first at the top
     * of the stack.
     */
    final Stack<E> previousElements = new Stack<>();

    /**
     * {@link #nextElements} if {@code next()} was called more recently then {@code previous},
     * {@link #previousElements} if the reverse is true, or -- overriding both of these -- {@code

   * putInstance(TypeToken.of(Foo.class), foo)}.
   *
   * @return the value previously associated with this class (possibly {@code null}), or {@code
   *     null} if there was no previous entry.
   */
  @CanIgnoreReturnValue
  <T extends B> @Nullable T putInstance(Class<@NonNull T> type, @ParametricNullness T value);

  /**

   * putInstance(TypeToken.of(Foo.class), foo)}.
   *
   * @return the value previously associated with this class (possibly {@code null}), or {@code
   *     null} if there was no previous entry.
   */
  @CanIgnoreReturnValue
  <T extends B> @Nullable T putInstance(Class<@NonNull T> type, @ParametricNullness T value);

  /**

    updater.lazySet(this, next);
  }

  /**
   * Atomically sets to the given value and returns the old value.
   *
   * @param newValue the new value
   * @return the previous value
   */
  public final double getAndSet(double newValue) {
    long next = doubleToRawLongBits(newValue);
    return longBitsToDouble(updater.getAndSet(this, next));
  }

  /**

/**
 * 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).
 *

   * 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}