private CommandStore(){
//regist the commands
tree_commands.put("addcartocross", new HackCarToCross());
tree_commands.put("exit", new Exit());
tree_commands.put("getcarfromcross", new GetCarFromCross());
tree_commands.put("getcarsfromroute", new GetCarsFromRoute());
tree_commands.put("getmaplist", new GetMapList());
tree_commands.put("getordinarycardetails", new GetOrdinaryCarDetails());
tree_commands.put("getpolicecardetails", new GetPoliceCarDetails());
tree_commands.put("getrobberycardetails", new GetRobberyCarDetails());
tree_commands.put("getrobberynextcrossouts", new GetRobberyNextCrossOuts());