public Object getValueAt(int row, int col) {
   if (row < data.size()) {
     GameObject obj = (GameObject) data.get(row);
     switch (col) {
       case 0:
         return new Long(obj.getId());
       case 1:
         return obj.getName();
       case 2:
         GameObject hb = obj.getHeldBy();
         return hb == null ? "" : hb.toString();
       case 3:
         return new Integer(obj.getHoldCount());
       default:
         throw new IllegalArgumentException("Invalid column index");
     }
   }
   return null;
 }