* stream may perform better.
   *
   * @see Stream#concat(Stream, Stream)
   */
  @SuppressWarnings("unchecked") // could probably be avoided with a forwarding Spliterator
  @SafeVarargs
  public static <T extends @Nullable Object> Stream<T> concat(Stream<? extends T>... streams) {
    // TODO(lowasser): consider an implementation that can support SUBSIZED

    if (!iterator.hasNext()) {
      return Optional.absent();
    }

    /*
     * TODO(kevinb): consider whether this "optimization" is worthwhile. Users with SortedSets tend
     * to know they are SortedSets and probably would not call this method.
     */
    if (iterable instanceof SortedSet) {
      SortedSet<E> sortedSet = (SortedSet<E>) iterable;
      return Optional.of(sortedSet.last());
    }

    while (true) {

       * that behavior is undefined when the backing map is modified through another API. (It even
       * permits us to throw IllegalStateException. Maybe we should have done that, but we probably
       * shouldn't change now for fear of breaking people.)
       */
      return (lastKnownIndex == -1) ? unsafeNull() : value(lastKnownIndex);
    }

    @Override
    @ParametricNullness

    }

    @Override
    int expectedValueCollectionSize(int defaultExpectedValues, Iterable<?> values) {
      // Only trust the size of `values` if it is a Set and therefore probably already deduplicated.
      if (values instanceof Set<?>) {
        Set<?> collection = (Set<?>) values;
        return max(defaultExpectedValues, collection.size());
      } else {
        return defaultExpectedValues;

     * accept that many elements.
     *
     * <p>This gets overridden in ImmutableSetMultimap.Builder to only trust the size of {@code
     * values} if it is a Set and therefore probably already deduplicated.
     */
    int expectedValueCollectionSize(int defaultExpectedValues, Iterable<?> values) {
      if (values instanceof Collection<?>) {
        Collection<?> collection = (Collection<?>) values;

    }

    @Override
    int expectedValueCollectionSize(int defaultExpectedValues, Iterable<?> values) {
      // Only trust the size of `values` if it is a Set and therefore probably already deduplicated.
      if (values instanceof Set<?>) {
        Set<?> collection = (Set<?>) values;
        return max(defaultExpectedValues, collection.size());
      } else {
        return defaultExpectedValues;

         * Thread.interrupt() (as discussed in InterruptibleTask). At the end of the day, it's
         * unlikely that cancel() will be slow, so we can probably get away with calling it while
         * holding a lock. Still, it would be nice to avoid somehow.
         */
        lock.lock();
        try {
          currentFuture.cancel(mayInterruptIfRunning);

   * </ul>
   *
   * <p>due to case-folding of some non-ASCII characters (which does not occur in {@link
   * String#equalsIgnoreCase}). However in almost all cases that ASCII strings are used, the author
   * probably wanted the behavior provided by this method rather than the subtle and sometimes
   * surprising behavior of {@code toUpperCase()} and {@code toLowerCase()}.
   *
   * @since 16.0
   */

      try {
        return target.contains(t);
      } catch (NullPointerException | ClassCastException e) {
        return false;
      }
    }

    @Override
    /*
     * We should probably not have implemented equals() at all, but given that we did, we can't
     * provide a better implementation than the input Collection, at least without dramatic changes

          && hashCodeInsensitiveToArgReference(
              factory, args, i, generateDummyArg(param, newFreshValueGenerator()))) {
        // If the implementation uses identityHashCode(), referential equality is
        // probably intended. So no point in using an equal-but-different factory argument.
        // We check twice to avoid confusion caused by accidental hash collision.
        equalArgs.set(i, shouldBeEqualArg);
      }
    }