java - 我如何将枚举与其相反的值关联起来，如在基本方向(北 - 南，东 - 西等)上？

Question

我仍在为我正在尝试制作的迷宫游戏编写 Cell 类(class)。在获得不同线程的帮助后，有人建议我为我的墙壁/邻居使用 EnumMap，到目前为止效果很好。

这是我目前所拥有的:

enum Dir {
    NORTH, SOUTH, EAST, WEST
}

class Cell {
    public Map<Dir, Cell> neighbors = Collections
            .synchronizedMap(new EnumMap<Dir, Cell>(Dir.class));
    public Map<Dir, Boolean> walls = Collections
            .synchronizedMap(new EnumMap<Dir, Boolean>(Dir.class));

    public boolean Visited;

    public Cell() {
        Visited = false;
        for (Dir direction : Dir.values()) {
            walls.put(direction, true);
        }
    }

    // Randomly select an unvisited neighbor and tear down the walls
    // between this cell and that neighbor.
    public Cell removeRandomWall() {
        List<Dir> unvisitedDirections = new ArrayList<Dir>();
        for (Dir direction : neighbors.keySet()) {
            if (!neighbors.get(direction).Visited)
                unvisitedDirections.add(direction);
        }

        Random randGen = new Random();
        Dir randDir = unvisitedDirections.get(randGen
                .nextInt(unvisitedDirections.size()));
        Cell randomNeighbor = neighbors.get(randDir);

        // Tear down wall in this cell
        walls.put(randDir, false);
        // Tear down opposite wall in neighbor cell
        randomNeighbor.walls.put(randDir, false); // <--- instead of randDir, it needs to be it's opposite.

        return randomNeighbor;
    }
}

如果你看那里的最后一条评论，我首先要拆除我当前牢房中的北墙。然后我带着我的北邻居，现在我必须拆除我的南墙，所以两个牢房之间的墙已经被拆除。

有什么简单的方法可以扩展我的枚举，以便我可以给它一个方向，然后它返回给我相反的方向？

Answer 1

还有另一种方式，无需 switch/case，也不必存储状态:

public enum Dir {
   NORTH { @Override public Dir opposite() { return SOUTH; }},
   EAST  { @Override public Dir opposite() { return WEST;  }},
   SOUTH { @Override public Dir opposite() { return NORTH; }},
   WEST  { @Override public Dir opposite() { return EAST;  }},
   ;

   abstract public Dir opposite();
}