code: public List<Notification> getByStep(int step) {
          List<Notification> found = new ArrayList<Notification>();
          for (Notification n: NotificationManager.notifications)
              if (n.getWhen() == step){
                  logger.fine("...found a match for getByStep query. With step: "+step);
                  found.add(n);
              }
          if(found.size()>0)        
              return found;
          return null;
      }
docs: Search for notifications saved on the given step.
  
  @param step
  the simulation step number from which the notifications are asked
  @return
  a List with the notifications that match the given step or null if no one can be found.