* of FutureValueReference).
     *
     * @throws ExecutionException if the loading thread throws an exception
     * @throws ExecutionError if the loading thread throws an error
     */
    V waitForValue() throws ExecutionException;

    /** Returns the weight of this entry. This is assumed to be static between calls to setValue. */
    int getWeight();

    /**

    public boolean isLoading() {
      return loading;
    }

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

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

    @Override
    public void notifyNewValue(V newValue) {}

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

    public boolean isLoading() {
      return loading;
    }

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

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

    @Override
    public void notifyNewValue(V newValue) {}

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