/** The list of callback listeners. */
private final List<HighLevelCallbackListener<R>> highLevelCallbackListeners = Collections.synchronizedList(new ArrayList<HighLevelCallbackListener<R>>());
/** Whether the result is complete. */
/** The list of callback listeners. */
private final List<HighLevelCallbackListener<R>> highLevelCallbackListeners = Collections.synchronizedList(new ArrayList<HighLevelCallbackListener<R>>());
/** Whether the result is complete. */