*
   * {@snippet :
   * awaitDone(new FinalizationPredicate() {
   *   public boolean isDone() {
   *     return ref.get() == null;
   *   }
   * });
   * }
   *
   * @throws RuntimeException if timed out or interrupted while waiting
   */
  public static void awaitClear(WeakReference<?> ref) {
    awaitDone(() -> ref.get() == null);
  }

  /**

   *
   * {@snippet :
   * awaitDone(new FinalizationPredicate() {
   *   public boolean isDone() {
   *     return ref.get() == null;
   *   }
   * });
   * }
   *
   * @throws RuntimeException if timed out or interrupted while waiting
   */
  public static void awaitClear(WeakReference<?> ref) {
    awaitDone(() -> ref.get() == null);
  }

  /**

          @Override
          protected void finalize() {
            future.set(null);
          }
        };
    unused = null; // Hint to the JIT that unused is unreachable
    GcFinalization.awaitDone(future);
    assertTrue(future.isDone());
    assertFalse(future.isCancelled());
  }

  public void testAwaitDone_future_cancel() {
    SettableFuture<@Nullable Void> future = SettableFuture.create();

          @Override
          protected void finalize() {
            future.set(null);
          }
        };
    unused = null; // Hint to the JIT that unused is unreachable
    GcFinalization.awaitDone(future);
    assertTrue(future.isDone());
    assertFalse(future.isCancelled());
  }

  public void testAwaitDone_future_cancel() {
    SettableFuture<@Nullable Void> future = SettableFuture.create();