}
    return false;
  }

  /**
   * Returns {@code element} cast to {@code E}, if it actually is a nonnull E. Otherwise, throws
   * either a NullPointerException or a ClassCastException as appropriate.
   */
  private void checkIsE(Object element) {
    checkNotNull(element);
    if (!isActuallyE(element)) {

    @Override
    public OutputStream openStream() {
      return ByteStreams.nullOutputStream();
    }
  }

  // Compare by toString() to satisfy 2 properties:
  // 1. compareTo(null) should throw NullPointerException
  // 2. the order is deterministic and easy to understand, for debugging purpose.
  @SuppressWarnings("ComparableType")
  private static final class ByToString implements Comparable<Object>, Serializable {

  }

  /**
   * A {@link Set} that throws {@link NullPointerException} and {@link ClassCastException} from
   * {@link #contains}.
   */
  private static final class SetContainsThrows extends AbstractSet<Void> {
    @Override
    public boolean contains(@Nullable Object o) {
      throw o == null ? new NullPointerException() : new ClassCastException();
    }

    @Override
    public int size() {

   * Objects.equals(o, element)} would return {@code true}. Otherwise returns {@code false}, even in
   * cases where {@link Collection#contains} might throw {@link NullPointerException} or {@link
   * ClassCastException}.
   */
  public static boolean contains(Iterable<?> iterable, @Nullable Object element) {
    if (iterable instanceof Collection) {

   *
   * @param collection a collection of {@code Boolean} objects
   * @return an array containing the same values as {@code collection}, in the same order, converted
   *     to primitives
   * @throws NullPointerException if {@code collection} or any of its elements is null
   */
  public static boolean[] toArray(Collection<Boolean> collection) {
    if (collection instanceof BooleanArrayAsList) {

   *
   * @param collection a collection of {@code Boolean} objects
   * @return an array containing the same values as {@code collection}, in the same order, converted
   *     to primitives
   * @throws NullPointerException if {@code collection} or any of its elements is null
   */
  public static boolean[] toArray(Collection<Boolean> collection) {
    if (collection instanceof BooleanArrayAsList) {

   *
   * @param collection a collection of {@code Number} instances
   * @return an array containing the same values as {@code collection}, in the same order, converted
   *     to primitives
   * @throws NullPointerException if {@code collection} or any of its elements is null
   * @since 1.0 (parameter was {@code Collection<Double>} before 12.0)
   */
  public static double[] toArray(Collection<? extends Number> collection) {

## Version 3.14.4

_2019-09-29_

 *  Fix: Cancel calls that fail due to unexpected exceptions. We had a bug where an enqueued call
    would never call back if it crashed with an unchecked throwable, such as a
    `NullPointerException` or `OutOfMemoryError`. We now call `Callback.onFailure()` with an
    `IOException` that reports the call as canceled. The triggering exception is still delivered to
    the thread's `UncaughtExceptionHandler`.

  @CanIgnoreReturnValue
  static Object checkElementNotNull(@Nullable Object element, int index) {
    if (element == null) {
      throw new NullPointerException("at index " + index);
    }
    return element;
  }

  @Override
  public void setUp() {
    fakePool = new FakeExecutor();
    e = new SequentialExecutor(fakePool);
  }

  public void testConstructingWithNullExecutor_fails() {
    assertThrows(NullPointerException.class, () -> new SequentialExecutor(null));
  }

  public void testBasics() {
    AtomicInteger totalCalls = new AtomicInteger();
    Runnable intCounter =
        new Runnable() {
          @Override