@Override
    public boolean isActive() {
      return !loading;
    }

    @Override
    public V waitForValue() {
      return get();
    }

    @Override
    public void notifyNewValue(V newValue) {}

    public void clear() {
      value = null;
    }
  }

  private static class SerializableCacheLoader extends CacheLoader<Object, Object>
      implements Serializable {