Platform.runLater

Question

I have and app that connects to a socket connection and that connections sends me a lot of info.. lets say 300 orders per second (maybe more).. I have a class (it is like a listener, that reacts to some event and that event has the order) that receives that order.. creates an object and then adds it to an ObservableList (which is the source of a tableView).. that way my GUI shows that order. But here comes the problem, if that order already exists on the observableList.. i can't add it ..and i must update it (wich i do).. but some times.. with some orders this condition doesn't work and the order its added again.

Im gonna show you how it's work with some code.

 public class ReceivedOrderListener 
 {
     ev = Event; //Supose that this is the event with the order
     if(!Repository.ordersIdMap.containsKey(ev.orderID))
     {    

         Platform.runLater(new Runnable() 
         {
            @Override public void run() 
            {                                                                    
                Repository.ordersCollection.add(ev.orderVo);                        
            }
         } 
      });
      Repository.ordersIdMap.put(ev.orderID, ev.orderVo);
  }

Ok now.. this is a resume of my code. The ev is my event with all the info of the order, the orderID is the key that i use to see if the order already exists or not (and yeah is unique). The "Repository" is a singleton class, the "ordersCollection" is a ObservableList, the "ordersIdMap" is a HashMap

Answer 1

If ReceivedOrderListener is executed by multiple threads, then it looks like "check-then-act" race condition.

-> ORDER1 comes to the listener
T1 checks ordersIdMap.containsKey(ORDER1) it returs false
T1 proceeds to do Platform.runLater to add the order
-> ORDER1 comes to the listener again
-> T2 checks ordersIdMap.containsKey(ORDER1) it returs false again
now T1 proceeds to do ordersIdMap.put(ORDER1)
-> T2 proceeds to do Platform.runLater to add the order again