* identifier} as the bus's name for logging purposes.
   *
   * @param identifier short name for the bus, for logging purposes.
   * @param executor Executor to use to dispatch events. It is the caller's responsibility to shut
   *     down the executor after the last event has been posted to this event bus.
   */
  public AsyncEventBus(String identifier, Executor executor) {

 * Iterator#remove} operations. This utility takes the brute-force approach of trying <i>all</i>
 * possible sequences of these operations, up to a given number of steps. So, if the caller
 * specifies to use <i>n</i> steps, a total of <i>3^n</i> tests are actually performed.
 *
 * <p>For instance, if <i>steps</i> is 5, one example sequence that will be tested is:
 *
 * <ol>
 *   <li>remove();

   * would declare a return type of `@Nullable T[]`. However, we've decided not to think too hard
   * about arrays for now, as they're a mess. (We previously discussed this in the review of
   * ObjectArrays, which is the main caller of this method.)
   */
  static <T extends @Nullable Object> T[] newArray(T[] reference, int length) {
    T[] empty = reference.length == 0 ? reference : Arrays.copyOf(reference, 0);
    return Arrays.copyOf(empty, length);

  /**
   * Returns the data to expect the source or sink to contain given the data that was used to create
   * the source or written to the sink. Typically, this will just return the input directly, but in
   * some cases it may alter the input. For example, if the factory returns a sliced view of a
   * source created with some given bytes, this method would return a subsequence of the given
   * (byte[]) data.
   */
  T getExpected(T data);

   * themselves their proper values under GWT, since GWT's EnumMap does need the Class instance.
   *
   * Note that sometimes these fields *do* have correct values under J2CL: They will if the caller
   * calls `create(Foo.class)`, rather than `create(map)`. That's fine; we just shouldn't rely on
   * it.
   */
  transient Class<K> keyTypeOrObjectUnderJ2cl;
  transient Class<V> valueTypeOrObjectUnderJ2cl;

  /**

    return new MutableClassToInstanceMap<>(new HashMap<Class<? extends @NonNull B>, B>());
  }

  /**
   * Returns a new {@code MutableClassToInstanceMap} instance backed by a given empty {@code
   * backingMap}. The caller surrenders control of the backing map, and thus should not allow any
   * direct references to it to remain accessible.
   */
  public static <B extends @Nullable Object> MutableClassToInstanceMap<B> create(

    }
  }

  /**
   * Views the array as an immutable list. The array must have only {@code E} elements.
   *
   * <p>The array must be internally created.
   */
  @SuppressWarnings("unchecked") // caller is reponsible for getting this right
  static <E> ImmutableList<E> asImmutableList(Object[] elements) {
    return unsafeDelegateList((List) Arrays.asList(elements));
  }

   * of tasks submitted by {@code invokeAll} or {@code invokeAny}, tasks will run serially on the
   * calling thread. Tasks are run to completion before a {@code Future} is returned to the caller
   * (unless the executor has been shutdown).
   *
   * <p>The returned executor is backed by the executor returned by {@link
   * MoreExecutors#newDirectExecutorService} and subject to the same constraints.
   *

   * advantages to having the type are the ability to use its constructor reference below and the
   * parallelism with the primitive version. In short, it makes its caller ({@code flatMap})
   * simpler.
   *
   * @param <InElementT> the element type of the input spliterator
   * @param <OutElementT> the element type of the output spliterators
   */

   * Optional.orElseGet}, except when {@code supplier} returns {@code null}. In this case this
   * method throws an exception, whereas the Java 8+ method returns the {@code null} to the caller.
   *
   * @throws NullPointerException if this optional's value is absent and the supplier returns {@code
   *     null}
   */
  public abstract T or(Supplier<? extends T> supplier);

  /**