//    it would just add an edge such that if done() observed non-null, then it would also
  //    definitely observe all earlier writes, but we still have no guarantee that done() would see
  //    the initial write (just stronger guarantees if it does).
  //
  // See: http://cs.oswego.edu/pipermail/concurrency-interest/2015-January/013800.html

    // There are several well-known algorithms for rotating part of an array (or, equivalently,
    // exchanging two blocks of memory). This classic text by Gries and Mills mentions several:
    // https://ecommons.cornell.edu/bitstream/handle/1813/6292/81-452.pdf.
    // (1) "Reversal", the one we have here.

other arm curled round her head.  Still she went on growing, and,
as a last resource, she put one arm out of the window, and one
foot up the chimney, and said to herself `Now I can do no more,
whatever happens.  What WILL become of me?'

  Luckily for Alice, the little magic bottle had now had its full
effect, and she grew no larger:  still it was very uncomfortable,

  }

  /**
   * Creates a TimeLimiter instance using the given executor service to execute method calls.
   *
   * <p><b>Warning:</b> using a bounded executor may be counterproductive! If the thread pool fills
   * up, any time callers spend waiting for a thread may count toward their time limit, and in this
   * case the call may even time out before the target method is ever invoked.
   *

  /**
   * Returns a view of {@code iterable} that skips its first {@code numberToSkip} elements. If
   * {@code iterable} contains fewer than {@code numberToSkip} elements, the returned iterable skips
   * all of its elements.
   *
   * <p>Modifications to the underlying {@link Iterable} before a call to {@code iterator()} are
   * reflected in the returned iterator. That is, the iterator skips the first {@code numberToSkip}

  public static RateLimiter create(double permitsPerSecond) {
    /*
     * The default RateLimiter configuration can save the unused permits of up to one second. This
     * is to avoid unnecessary stalls in situations like this: A RateLimiter of 1qps, and 4 threads,
     * all calling acquire() at these moments:
     *
     * T0 at 0 seconds
     * T1 at 1.05 seconds
     * T2 at 2 seconds
     * T3 at 3 seconds

other arm curled round her head.  Still she went on growing, and,
as a last resource, she put one arm out of the window, and one
foot up the chimney, and said to herself `Now I can do no more,
whatever happens.  What WILL become of me?'

  Luckily for Alice, the little magic bottle had now had its full
effect, and she grew no larger:  still it was very uncomfortable,

   *     Queue<Integer>} but not a {@code Queue<Object>}).
   * @since 8.0
   */
  public static final class Builder<B> {
    /*
     * TODO(kevinb): when the dust settles, see if we still need this or can
     * just default to DEFAULT_CAPACITY.
     */
    private static final int UNSET_EXPECTED_SIZE = -1;

    private final Comparator<B> comparator;

             * exception in seenExceptions. When we complete secondFuture with the same exception,
             * we want for AggregateFuture to still detect that it's been previously seen.
             */
            secondFuture.setException(sameInstance);
          }
        },
        directExecutor());
    firstFuture.setException(sameInstance);