Question

我需要能够从另一个HashMap中的HashMap获取值。我对HashMaps并不是那么熟悉所以我自己也无法解决这个问题。代码：

import java.util.HashMap;

public class testfile2 {
    public static void main(String args[]){

        HashMap<String, HashMap<String, String>> rooms = new HashMap<String, HashMap<String, String>>();

        HashMap<String,String> roomA = new HashMap<String,String>();
        roomA.put("desc1","You are in a dark room made out of wood. Some light shines through a window to the South.From this light you can make out a door to the East");
        roomA.put("desc2", "You are in a dark room made out of wood. Some light shines through a broken window to the South.From this light you can make out a door to the East. There is a tunnel leading outwards from the window.");
        rooms.put("roomA", roomA);

        HashMap<String, String> roomB = new HashMap<String, String>();
        roomB.put("desc1", "You are in a dark wooden room. There is nothing here but a doorway leading to the West.");
        roomB.put("desc2", "You are in a dark wooden room. There is a doorway that leads to the West. There is also an axe you can take on the ground.");
        rooms.put("roomB", roomB);

        HashMap<String, String> roomC = new HashMap<String, String>();
        roomC.put("desc1", "You are in a completely white rectangular room. There is a rectangular hole in the wall to the North.");
        rooms.put("roomC", roomC);

        System.out.print(rooms.get("roomA"));

    }
}

我需要能够打电话给＃34; desc1＆＃34;来自字符串＆＃34; roomA＆＃34;那是在HashMap房间里。

进一步澄清：System.out.print（rooms.get（＆＃34; roomA＆＃34; .get（＆＃34; desc1＆＃34;））; 上面的印刷声明就像我需要的东西。我知道我不能使用String＆＃34; roomA＆＃34;使用.get，但如果有任何办法可以做到这一点，我真的很感激一些帮助。

Answer 1

rooms.get("roomA").get("desc1")是简短的回答。由于你是HashMaps的新手，让我们澄清一下。

rooms是HashMap，它将字符串映射到HashMap<String, String>。因此，您在房间呼叫的每个.get(...)都有HashMap<String, String>的返回类型。在.get(...)的任何内容上调用HashMap<String, String>都会返回String类型的值，这就是您的目标。

因此

rooms.get("roomA")

返回HashMap<String,String>和

rooms.get("roomA").get("desc1")

返回String。

另一种思考方式是将其分为两个陈述：

HashMap<String, String> myRoom = rooms.get("roomA");
String desc = myRoom.get("desc1");

然后可以很容易地将其压缩到rooms.get("roomA").get("desc1")。

Answer 2

rooms.get("roomA").get("desc1")应该有用。

当然最好检查是否存在，以避免潜在的NullPointerException：

if (rooms.get("roomA") != null) {
    System.out.println(rooms.get("roomA").get("desc1"));
}

HashMap里面涉及字符串的Hashmap打印？

2 个答案: