*
   * @param future The future attach the callback to.
   * @param callback The callback to invoke when {@code future} is completed.
   * @param executor The executor to run {@code callback} when the future completes.
   * @since 10.0
   */
  public static <V extends @Nullable Object> void addCallback(
      final ListenableFuture<V> future,
      final FutureCallback<? super V> callback,
      Executor executor) {

        // Some Android 5.0.x Samsung devices have bugs in JDK reflection APIs that cause
        // getDeclaredField to throw a NoSuchFieldException when the field is definitely there.
        // For these users fallback to a suboptimal implementation, based on synchronized. This will
        // be a definite performance hit to those users.
        thrownAtomicReferenceFieldUpdaterFailure = atomicReferenceFieldUpdaterFailure;

    assertThat(units).isEmpty();
  }

  public void testToImmutableEnumSetReused() {
    // The method call lets us capture the accumulator as an A and invoke the callbacks manually
    genericTestToImmutableEnumSetReused(Sets.<SomeEnum>toImmutableEnumSet());
  }

  private static <A extends @Nullable Object> void genericTestToImmutableEnumSetReused(