code: public static synchronized DeckReference getDeckReference(int player, int hotCue) {
          Map<Integer, DeckReference> playerMap = instances.get(player);
          if (playerMap == null) {
              playerMap = new HashMap<Integer, DeckReference>();
              instances.put(player, playerMap);
          }
          DeckReference result = playerMap.get(hotCue);
          if (result == null) {
              result = new DeckReference(player, hotCue);
              playerMap.put(hotCue, result);
          }
          return result;
      }
docs: Get a unique reference to a place where a track is currently loaded in a player.
  
  @param player the player in which the track is loaded
  @param hotCue hot cue number in which the track is loaded, or 0 if it is actively loaded on the playback deck
  
  @return the instance that will always represent a reference to the specified player and hot cue