code: public void setAsyncListeners(Collection<CustomizationSupplier<CacheEntryOperationListener<K,V>>> c) {
      getAsyncListeners().addAll(c);
    }
docs: Adds the collection of customizations to the existing list. This method is intended to
  improve integration with bean configuration mechanisms that use the set method and
  construct a set or list, like Springs' bean XML configuration.