final L listener;
    final Executor executor;

    @GuardedBy("this")
    final Queue<ListenerCallQueue.Event<L>> waitQueue = Queues.newArrayDeque();

    @GuardedBy("this")
    final Queue<Object> labelQueue = Queues.newArrayDeque();

    @GuardedBy("this")
    boolean isThreadScheduled;

    PerListenerQueue(L listener, Executor executor) {
      this.listener = checkNotNull(listener);

   *
   * @since 12.0
   */
  public static <E> ArrayDeque<E> newArrayDeque() {
    return new ArrayDeque<>();
  }

  /**
   * Creates an {@code ArrayDeque} containing the elements of the specified iterable, in the order
   * they are returned by the iterable's iterator.
   *
   * @since 12.0
   */
  public static <E> ArrayDeque<E> newArrayDeque(Iterable<? extends E> elements) {
    if (elements instanceof Collection) {

    private final ThreadLocal<Queue<Event>> queue =
        new ThreadLocal<Queue<Event>>() {
          @Override
          protected Queue<Event> initialValue() {
            return Queues.newArrayDeque();
          }
        };

    /** Per-thread dispatch state, used to avoid reentrant event dispatching. */
    private final ThreadLocal<Boolean> dispatching =
        new ThreadLocal<Boolean>() {

     *
     * @param <E>
     *            {@link ArrayDeque}の要素型
     * @return {@link ArrayDeque}の新しいインスタンス
     * @see ArrayDeque#ArrayDeque()
     */
    public static <E> ArrayDeque<E> newArrayDeque() {
        return new ArrayDeque<>();
    }

    /**
     * {@link ArrayDeque}の新しいインスタンスを作成して返します。
     *
     * @param <E>
     *            {@link ArrayDeque}の要素型
     * @param c