* #enqueue enqueued} and {@link #dispatch dispatched}.
   */
  public void addListener(L listener, Executor executor) {
    checkNotNull(listener, "listener");
    checkNotNull(executor, "executor");
    listeners.add(new PerListenerQueue<>(listener, executor));
  }

  /**
   * Enqueues an event to be run on currently known listeners.
   *

    public void twoArg(String s, Integer i) {
      checkNotNull(s);
      i.intValue();
    }

    public void twoMixedArgs(String s, @Nullable Integer i) {
      checkNotNull(s);
    }

    public void twoMixedArgs(@Nullable Integer i, String s) {
      checkNotNull(s);
    }

    public void twoMixedArgsThrows(String s, @Nullable Integer i) {
      checkNotNull(s);
      doThrow(i);
    }

    for (int i = 0; i < len; i++) {
      // checkNotNull for GWT (do not optimize)
      array[i] = (Character) checkNotNull(boxedArray[i]);
    }
    return array;
  }

  /**
   * Sorts the elements of {@code array} in descending order.
   *
   * @since 23.1
   */
  public static void sortDescending(char[] array) {
    checkNotNull(array);
    sortDescending(array, 0, array.length);
  }

  }

  @Override
  public boolean hasEdgeConnecting(N nodeU, N nodeV) {
    checkNotNull(nodeU);
    checkNotNull(nodeV);
    return nodes().contains(nodeU) && successors(nodeU).contains(nodeV);
  }

  @Override
  public boolean hasEdgeConnecting(EndpointPair<N> endpoints) {
    checkNotNull(endpoints);
    if (!isOrderingCompatible(endpoints)) {
      return false;
    }

    public Builder<E> add(E... elements) {
      checkNotNull(elements); // for GWT
      for (E element : elements) {
        add(checkNotNull(element));
      }
      return this;
    }

    @CanIgnoreReturnValue
    public Builder<E> addAll(Iterable<? extends E> elements) {
      checkNotNull(elements); // for GWT
      for (E element : elements) {
        add(checkNotNull(element));
      }
      return this;

    return connections;
  }

  @Override
  @CanIgnoreReturnValue
  @CheckForNull
  public V putEdgeValue(N nodeU, N nodeV, V value) {
    checkNotNull(nodeU, "nodeU");
    checkNotNull(nodeV, "nodeV");
    checkNotNull(value, "value");

    if (!allowsSelfLoops()) {
      checkArgument(!nodeU.equals(nodeV), SELF_LOOPS_NOT_ALLOWED, nodeU);
    }

  private final Random random;

  public RandomAmountInputStream(InputStream in, Random random) {
    super(checkNotNull(in));
    this.random = checkNotNull(random);
  }

  @Override
  public int read(byte[] b, int off, int len) throws IOException {
    return super.read(b, off, random.nextInt(len) + 1);
  }

    }
    return map;
  }

  @CanIgnoreReturnValue
  @Override
  @CheckForNull
  public V put(R rowKey, C columnKey, V value) {
    checkNotNull(rowKey);
    checkNotNull(columnKey);
    checkNotNull(value);
    return getOrCreate(rowKey).put(columnKey, value);
  }

  @CanIgnoreReturnValue
  @Override
  @CheckForNull

    TrustedFutureInterruptibleAsyncTask(AsyncCallable<V> callable) {
      this.callable = checkNotNull(callable);
    }

    @Override
    final boolean isDone() {
      return TrustedListenableFutureTask.this.isDone();
    }

    @Override
    ListenableFuture<V> runInterruptibly() throws Exception {
      return checkNotNull(
          callable.call(),
          "AsyncCallable.call returned null instead of a Future. "

    return connections;
  }

  @Override
  @CanIgnoreReturnValue
  public boolean addEdge(N nodeU, N nodeV, E edge) {
    checkNotNull(nodeU, "nodeU");
    checkNotNull(nodeV, "nodeV");
    checkNotNull(edge, "edge");

    if (containsEdge(edge)) {
      EndpointPair<N> existingIncidentNodes = incidentNodes(edge);