Question

我是Java新手，我想要做的是将HashMap（ hm ）的所有键和值交换为HashMap（ hm2 ），反之亦然。我没有为这个问题找到任何解决方案，有可能吗？

import java.util.*;

class HashMapSwap{
public static void main(String args[]){
    HashMap<Integer, String> hm = new HashMap<Integer, String>();
    HashMap<Integer, String> hm2 = new HashMap<Integer, String>();

    hm.put(3, "Mobile");
    hm.put(11, "Tab");

    hm2.put(4, "PC");
    hm2.put(1, "Laptop");

    Map tmp = new HashMap(hm);
    tmp.keySet().removeAll(hm2.keySet());
    hm2.putAll(tmp);

    for(Map.Entry en:hm2.entrySet()){
        System.out.println(en.getKey() + " " + en.getValue());
    }
}
}

O / P：

1台笔记本电脑

3手机

4 PC

11标签

Answer 1

// store first map in (new) temporary map
HashMap<Integer, String> tempMap = new HashMap<Integer, String>(hm);

// clear first map and store pairs of hm2
hm.clear();
hm.putAll(hm2);

// clear second map and store pairs of tempMap
hm2.clear();
hm2.putAll(tempMap);

// EDIT (hint from Palcente)
// optional: null the tempMap afterwards
tempMap = null;

Answer 2

tmp可用于交换引用，如下所示。

        HashMap<Integer, String> hm = new HashMap<Integer, String>();
        HashMap<Integer, String> hm2 = new HashMap<Integer, String>();

        hm.put(3, "Mobile");
        hm.put(11, "Tab");

        hm2.put(4, "PC");
        hm2.put(1, "Laptop");

        HashMap tmp = new HashMap();
        tmp = hm;
        hm = hm2;
        hm2 = tmp;

        for(Map.Entry en:hm.entrySet()){
            System.out.println(en.getKey() + " " + en.getValue());
        }
        for(Map.Entry en:hm2.entrySet()){
            System.out.println(en.getKey() + " " + en.getValue());
        }

我可以将HashMap键和值交换到其他键吗？

2 个答案: