`What IS the fun?' said Alice.

  `Why, SHE,' said the Gryphon.  `It's all her fancy, that:  they
never executes nobody, you know.  Come on!'

  `Everybody says "come on!" here,' thought Alice, as she went
slowly after it:  `I never was so ordered about in all my life,
never!'

  They had not gone far before they saw the Mock Turtle in the
distance, sitting sad and lonely on a little ledge of rock, and,

    future1.set(1L);
    future1 = null;
    future2.set(2L);
    future2 = null;

    /*
     * Futures should be collected even if combiner never runs. This is kind of a silly test, since
     * the combiner is almost certain to hold its own reference to the futures, and a real app would

                        .expireAfterAccess(1, SECONDS)
                        .ticker(new SerializableTicker())))
            .named("LocalCache with expireAfterAccess") // SerializableTicker never advances
            .withFeatures(
                CollectionSize.ANY,
                MapFeature.GENERAL_PURPOSE,
                CollectionFeature.SUPPORTS_ITERATOR_REMOVE)
            .createTestSuite());

                        .expireAfterAccess(1, SECONDS)
                        .ticker(new SerializableTicker())))
            .named("LocalCache with expireAfterAccess") // SerializableTicker never advances
            .withFeatures(
                CollectionSize.ANY,
                MapFeature.GENERAL_PURPOSE,
                CollectionFeature.SUPPORTS_ITERATOR_REMOVE)
            .createTestSuite());

        }

        @Override
        public void notifyNewValue(Object newValue) {}
      };

  /** Singleton placeholder that indicates a value is being loaded. */
  @SuppressWarnings("unchecked") // impl never uses a parameter or returns any non-null value
  static <K, V> ValueReference<K, V> unset() {
    return (ValueReference<K, V>) UNSET;
  }

  private enum NullEntry implements ReferenceEntry<Object, Object> {

    future1.set(1L);
    future1 = null;
    future2.set(2L);
    future2 = null;

    /*
     * Futures should be collected even if combiner never runs. This is kind of a silly test, since
     * the combiner is almost certain to hold its own reference to the futures, and a real app would

  `What IS the fun?' said Alice.

  `Why, SHE,' said the Gryphon.  `It's all her fancy, that:  they
never executes nobody, you know.  Come on!'

  `Everybody says "come on!" here,' thought Alice, as she went
slowly after it:  `I never was so ordered about in all my life,
never!'

  They had not gone far before they saw the Mock Turtle in the
distance, sitting sad and lonely on a little ledge of rock, and,

        }

        @Override
        public void notifyNewValue(Object newValue) {}
      };

  /** Singleton placeholder that indicates a value is being loaded. */
  @SuppressWarnings("unchecked") // impl never uses a parameter or returns any non-null value
  static <K, V> ValueReference<K, V> unset() {
    return (ValueReference<K, V>) UNSET;
  }

  private enum NullEntry implements ReferenceEntry<Object, Object> {

    return new IdentityHashMap<>();
  }

  /**
   * Computes the difference between two maps. This difference is an immutable snapshot of the state
   * of the maps at the time this method is called. It will never change, even if the maps change at
   * a later time.
   *
   * <p>Since this method uses {@code HashMap} instances internally, the keys of the supplied maps

   *     Executor)}.
   * @param closingExecutor the future's result will be closed on this executor
   * @deprecated Creating {@link Future}s of closeable types is dangerous in general because the
   *     underlying value may never be closed if the {@link Future} is canceled after its operation
   *     begins. Consider replacing code that creates {@link ListenableFuture}s of closeable types,