/**
     * Notify pending loads that a new value was set. This is only relevant to loading value
     * references.
     */
    void notifyNewValue(@CheckForNull V newValue);

    /**
     * Returns true if a new value is currently loading, regardless of whether there is an existing

    @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 {

    @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 {