assertSame(refreshKey, map.get(refreshKey));

    new Thread() {
      @Override
      public void run() {
        cache.getUnchecked(getKey);
        getFinishedSignal.countDown();
      }
    }.start();
    new Thread() {
      @Override
      public void run() {
        cache.refresh(refreshKey);
        getFinishedSignal.countDown();
      }
    }.start();

    assertSame(refreshKey, map.get(refreshKey));

    new Thread() {
      @Override
      public void run() {
        cache.getUnchecked(getKey);
        getFinishedSignal.countDown();
      }
    }.start();
    new Thread() {
      @Override
      public void run() {
        cache.refresh(refreshKey);
        getFinishedSignal.countDown();
      }
    }.start();

     */
    public ListenableFuture<?> run(final Runnable combiner, Executor executor) {
      return call(
          new Callable<@Nullable Void>() {
            @Override
            @CheckForNull
            public Void call() throws Exception {
              combiner.run();
              return null;
            }
          },
          executor);
    }

    SetFuture(AbstractFuture<V> owner, ListenableFuture<? extends V> future) {
      this.owner = owner;
      this.future = future;
    }

    @Override
    public void run() {
      if (owner.value != this) {
        // nothing to do, we must have been cancelled, don't bother inspecting the future.
        return;
      }
      Object valueToSet = getFutureValue(future);

    try {
      Sets.cartesianProduct(set, set, set, set, set);
      fail("Expected IAE");
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testCartesianProduct_hashCode() {
    // Run through the same cartesian products we tested above

    Set<List<Integer>> degenerate = Sets.cartesianProduct();
    checkHashCode(degenerate);

    checkHashCode(Sets.cartesianProduct(set(1, 2)));

   *
   * <p>This must be a (2^n)-1 as it is used as a mask.
   */
  static final int DRAIN_THRESHOLD = 0x3F;

  /**
   * Maximum number of entries to be drained in a single cleanup run. This applies independently to
   * the cleanup queue and both reference queues.
   */
  // TODO(fry): empirically optimize this
  static final int DRAIN_MAX = 16;

  // Fields

  /**

    }

    @Override
    public @NonNull T next() {
      T result = valueOrNull;
      valueOrNull = null;
      // We put the common case first, even though it's unlikely to matter if the code is run much:
      // https://shipilev.net/jvm/anatomy-quarks/28-frequency-based-code-layout/
      if (result != null) {
        return result;
      }
      throw new NoSuchElementException();
    }
  }