无法将对象放入连接到其他对象的hashmap中

Question

我正在制作这个基于控制台的游戏。

但我不明白这一点，也不明白为什么这样做是错误的。

所以基本上我有10个房间，所以一个房间有以下东西：

-房间号码

-hashmap，其中包含一个Room作为值和一个String作为键

现在的问题是，一个房间可以从4个方向北、东、南、西退出，所以这是哈希图中的字符串/键。
它也可以有2个出口或1或3个。
所以在那个哈希图中，我将方向保存为键和值另一个房间对象，这样我就可以跟踪哪个出口去哪个房间。

所以我有一个添加出口的方法。看起来是这样的：

public class Room {
    private int RoomNo;
    private HashMap<String, Room> Exits;

    html" target="_blank">public Room(int roomNo){
        Exits = new HashMap<String, Room>();
        this.RoomNo = roomNo;

    }

    public void Addexits(Room room, String exitDirection){
            Exits.put(exitDirection,room);
    }

在游戏类中，我创建了10个房间，并使用call the addexits方法添加如下所示的出口：

Rooms = new ArrayList<Room>();
     //initialize all rooms
     room1 = new Room(1);
     room1.Addexits(room4,"West");
     room1.Addexits(room3,"East");
     room2 = new Room(2);
     room2.Addexits(room2,"North");
     room2.Addexits(room2,"South");
     room3 = new Room(3);
     room3.Addexits(room3,"West");
     room3.Addexits(room3,"East");
     room4 = new Room(4);
     room4.Addexits(room4,"West");
     room4.Addexits(room4,"East");

然而，正如您在room1中所看到的，我尝试在room4中添加2个出口，在room4中添加1个出口，在room3中添加1个出口，但是当我运行此操作时，它会在hashmap中显示：west-

但是，当我添加两个出口，都是对象room1时，它应该是这样的：

西-

所以我真的不知道我做错了什么每个房间在创建时都有自己的hashmap，房间已经创建好了，所以这不应该是个问题。

Answer 1

这是因为当您调用Addexits（）时，不能保证您添加的房间已经存在。因此，改变你的陈述应该可以解决这个问题。

Rooms = new ArrayList<Room>();
//initialize all rooms
room1 = new Room(1);
room2 = new Room(2);
room3 = new Room(3);
room4 = new Room(4);

// add all exits
room1.Addexits(room4,"West");
room1.Addexits(room3,"East");

room2.Addexits(room2,"North");
room2.Addexits(room2,"South");

room3.Addexits(room3,"West");
room3.Addexits(room3,"East");

room4.Addexits(room4,"West");
room4.Addexits(room4,"East");

还要注意，您正在将room3添加为room3的出口，对于Room2和4也是如此。我不知道这是不是目的。

Answer 2

在以下代码中

Rooms = new ArrayList<Room>();
 //initialize all rooms
 room1 = new Room(1);
 room1.Addexits(room4,"West");
 room1.Addexits(room3,"East");

你正在添加还没有初始化的房间3和房间4。你刚刚声明了它。这就是你变得空的原因。初始化后试着添加它。

Rooms = new ArrayList<Room>();
 //initialize all rooms
 room1 = new Room(1);
 room2 = new Room(2);
 room2.Addexits(room2,"North");
 room2.Addexits(room2,"South");
 room3 = new Room(3);
 room3.Addexits(room3,"West");
 room3.Addexits(room3,"East");
 room4 = new Room(4);
 room4.Addexits(room4,"West");
 room4.Addexits(room4,"East");
 //here you add room4 and room3 exits
 room1.Addexits(room4,"West");
 room1.Addexits(room3,"East");

Answer 3

首先初始化所有房间，然后添加出口；

 room1 = new Room(1);
 room2 = new Room(2);
 room3 = new Room(3);
 room4 = new Room(4);
 room1.Addexits(room4,"West");
 room1.Addexits(room3,"East");
 room2.Addexits(room2,"North");
 room2.Addexits(room2,"South");
 room3.Addexits(room3,"West");
 room3.Addexits(room3,"East");
 room4.Addexits(room4,"West");
 room4.Addexits(room4,"East");