code: public void sendToUserDirect(String topicURI, Object event, String user) {
  		sendToUsersDirect(topicURI, event, Collections.singleton(user));
  	}
docs: Send an EventMessage directly to the client specified with the user parameter. If
  there is no entry in the {@link SimpUserRegistry} for this user nothing happens.
  <p>
  In contrast to {@link #sendToUser(String, Object, String)} this method does not
  check if the receiver is subscribed to the destination. The
  {@link SimpleBrokerMessageHandler} is not involved in sending this message.
  
  @param topicURI the name of the topic
  @param event the payload of the {@link EventMessage}
  @param user receiver of the EVENT message