* cancelled without a call to {@code cancel}, such as by calling {@code
   * setFuture(cancelledFuture)}.
   *
   * <p>Beware of completing a future while holding a lock. Its listeners may do slow work or
   * acquire other locks, risking deadlocks.
   */
  @CanIgnoreReturnValue
  @Override
  public boolean cancel(boolean mayInterruptIfRunning) {
    Object localValue = value;
    boolean rValue = false;

   * java.util.stream.Stream#filter}. This method is not being deprecated, but we gently encourage
   * you to migrate to streams.
   */
  // TODO(kevinb): how to omit that last sentence when building GWT javadoc?
  public static <E extends @Nullable Object> Set<E> filter(
      Set<E> unfiltered, Predicate<? super E> predicate) {
    if (unfiltered instanceof SortedSet) {

      }
    }.test();
  }

  @GwtIncompatible // slow (~5s)
  public void testConcatNoIteratorsYieldsEmpty() {
    new EmptyIteratorTester() {
      @Override
      protected Iterator<Integer> newTargetIterator() {
        return Iterators.concat();
      }
    }.test();
  }

  @GwtIncompatible // slow (~5s)
  public void testConcatOneEmptyIteratorYieldsEmpty() {

     * Exception.)
     */
    throw new UncheckedExecutionException(cause);
  }

  /*
   * Arguably we don't need a timed getUnchecked because any operation slow enough to require a
   * timeout is heavyweight enough to throw a checked exception and therefore be inappropriate to
   * use with getUnchecked. Further, it's not clear that converting the checked TimeoutException to