* avoid memory leaks when an element is no longer necessary.
   *
   * <p>This method accepts an array with element type {@code @Nullable T}, but callers must pass an
   * array whose contents are initially non-null. The {@code @Nullable} annotation indicates that
   * this method will write nulls into the array during iteration.
   *

    TrustedListenableFutureTask<O> task = TrustedListenableFutureTask.create(callable);
    Future<?> scheduled = executorService.schedule(task, delay, timeUnit);
    /*
     * Even when the user interrupts the task, we pass `false` to `cancel` so that we don't
     * interrupt a second time after the interruption performed by TrustedListenableFutureTask.
     */
    task.addListener(() -> scheduled.cancel(false), directExecutor());

   *
   * <p><b>Note:</b> The returned view performs slightly better when {@code set1} is the smaller of
   * the two sets. If you have reason to believe one of your sets will generally be smaller than the
   * other, pass it first. Unfortunately, since this method sets the generic type of the returned
   * set based on the type of the first set passed, this could in rare cases force you to make a
   * cast, for example:
   *
   * {@snippet :

   * take a principled stand on this, but the amount of such code is simply overwhelming. To avoid
   * creating a lot of compile errors that users would not find to be informative, we're giving in
   * and allowing callers to pass arguments that a nullness checker believes could be null.
   *
   * We still encourage people to use requireNonNull over checkNotNull for non-precondition checks.
   */

  /**

    overrides the stored "Content-Encoding" header.
 *  Fix: Gracefully shut down the HTTP/2 connection before it exhausts the
    namespace of stream IDs (~536 million streams).
 *  Fix: Never pass a null `Route` to `Authenticator`. There was a bug where
    routes were omitted for eagerly-closed connections.

## Version 3.9.1

_2017-11-18_

  /**
   * The elements in this map would pass the UNDER test, but are known not to be public suffixes and
   * are thus excluded from consideration. Since it refers to elements in UNDER of the same type,