code: public void addEventData(CacheEventData cacheEventData) {
          if (events == null) {
              events = new HashSet<CacheEventData>();
          }
          this.events.add(cacheEventData);
      }
docs: Helper method for adding multiple CacheEventData into this Set
  @param cacheEventData event data representing a single event's data.
  @see CacheEventData