return CollectCollectors.toImmutableSetMultimap(keyFunction, valueFunction);
  }

  /**
   * Returns a {@code Collector} accumulating entries into an {@code ImmutableSetMultimap}. Each
   * input element is mapped to a key and a stream of values, each of which are put into the
   * resulting {@code Multimap}, in the encounter order of the stream and the encounter order of the
   * streams of values.
   *
   * <p>Example:
   *

 * conformance of concrete {@link Map} subclasses to that contract.
 *
 * @param <K> the type of keys used by the maps under test
 * @param <V> the type of mapped values used the maps under test
 * @author George van den Driessche
 */
// TODO: Descriptive assertion messages, with hints as to probable fixes.

   * ImmutableSortedSet}, ordered by the specified comparator.
   *
   * <p>If the elements contain duplicates (according to the comparator), only the first duplicate
   * in encounter order will appear in the result.
   *
   * @since 33.2.0 (available since 21.0 in guava-jre)
   */
  @SuppressWarnings({"AndroidJdkLibsChecker", "Java7ApiChecker"})

/**
 * GWT emulated version of {@link com.google.common.collect.ImmutableSet}. For the unsorted sets,
 * they are thin wrapper around {@link java.util.Collections#emptySet()}, {@link
 * Collections#singleton(Object)} and {@link java.util.LinkedHashSet} for empty, singleton and
 * regular sets respectively. For the sorted sets, it's a thin wrapper around {@link
 * java.util.TreeSet}.
 *
 * @see ImmutableSortedSet
 * @author Hayward Chan
 */

   * and values are the result of applying the provided mapping functions to the input elements.
   * Entries appear in the result {@code ImmutableMap} in encounter order.
   *
   * <p>If the mapped keys contain duplicates (according to {@link Object#equals(Object)}, an {@code
   * IllegalArgumentException} is thrown when the collection operation is performed. (This differs

  /** An implementation of {@link List#subList(int, int)}. */
  static <E extends @Nullable Object> List<E> subListImpl(
      final List<E> list, int fromIndex, int toIndex) {
    List<E> wrapper;
    if (list instanceof RandomAccess) {
      wrapper =
          new RandomAccessListWrapper<E>(list) {
            @Override
            public ListIterator<E> listIterator(int index) {
              return backingList.listIterator(index);

    WrapperException(Throwable t) {
      super(t);
    }
  }

  private static void rethrow(ExecutionException e) throws ExecutionException {
    Throwable wrapper = e.getCause();
    if (wrapper instanceof WrapperException) {
      Throwable cause = wrapper.getCause();
      if (cause instanceof RuntimeException) {
        throw (RuntimeException) cause;
      } else if (cause instanceof Error) {
        throw (Error) cause;

 *   <li>enqueuing weak references to unreachable referents in their reference queue
 * </ul>
 *
 * <p>This class uses (possibly repeated) invocations of {@link java.lang.System#gc()} to cause
 * finalization to happen. However, a call to {@code System.gc()} is specified to be no more than a
 * hint, so this technique may fail at the whim of the JDK implementation, for example if a user

  /**
   * Returns a {@code Collector} that accumulates the input elements into a new {@code
   * ImmutableSet}. Elements appear in the resulting set in the encounter order of the stream; if
   * the stream contains duplicates (according to {@link Object#equals(Object)}), only the first
   * duplicate in encounter order will appear in the result.
   *
   * @since 21.0
   */
  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {

    SettableFuture<Foo> input = SettableFuture.create();
    ListenableFuture<Foo> wrapper = nonCancellationPropagating(input);
    Foo foo = new Foo();

    assertFalse(wrapper.isDone());
    input.set(foo);
    assertTrue(wrapper.isDone());
    assertSame(foo, getDone(wrapper));
  }

  public void testNonCancellationPropagating_failure() throws Exception {