private void build_rooms(){
        int[] roomNum = {101,102,103,104,105,106,107,108,109,110,
        201,202,203,204,205,206,207,208,209,210,
        301,302,303,304,305,306,307,308,309,310};

        for(int i=0; i<NUM_ROOMS;i++){
            Room room = new Room(roomNum[i]);
            allRooms.push(room);
        }
    }