用Java复制映射对象

Question

我试图采用与<如何在Java中复制对象>。

但在以下代码中，它不适用于Map对象。我想将原始地图数据复制到currMap。当前输出为

0
1
2
3
null
null

我希望它是

0
1
2
3
0
2
3

这里缺少什么？

import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Queue;
class mapCopy{
private Map<Character, Queue<Integer>> map;
mapCopy(Map<Character, Queue<Integer>> map){
this.map=map;
}

mapCopy(mapCopy mapcopy){
this.map=mapcopy.map;
}

Map<Character, Queue<Integer>> getMap(){
return this.map;
}
}
public class Test {
static Map<Character, Queue<Integer>> BuildMap(){
String toMatch="able";
Map<Character, Queue<Integer>> map = new HashMap<>();

int i=0;
for(var c:toMatch.toCharArray()) {
Queue<Integer> q = map.get(c);
if(q==null)
q=new ArrayDeque<Integer>();

q.add(i);
map.put(c, q);          
i++;
}

return map;
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Map<Character, Queue<Integer>> map = BuildMap();

List<String> dic = Arrays.asList("able", "ale");        

for(var d:dic) {
var copy1 = new mapCopy(map);
var copy2 = new mapCopy(copy1);

var currMap = copy2.getMap();

for(var c:d.toCharArray()) {        
System.out.println(currMap.get(c).poll());
}
}
}
}

更新1:

iota的答案就是我想要的。以下是通过添加copyMap函数并将其添加到currMap(var currMap=copyMap(map(；(

不需要类mapCopy。

static Map<Character, Queue<Integer>> copyMap(Map<Character, Queue<Integer>> mapcopy){
Map<Character, Queue<Integer>> map = new HashMap<>(mapcopy.size());
mapcopy.forEach((k,v)->{
map.put(k, new ArrayDeque<>(v));
});

return map;
}

更新2:
添加完整的代码

import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Queue;
public class Test {
static Map<Character, Queue<Integer>> BuildMap(){
String toMatch="able";
Map<Character, Queue<Integer>> map = new HashMap<>();

int i=0;
for(var c:toMatch.toCharArray()) {
Queue<Integer> q = map.get(c);
if(q==null)
q=new ArrayDeque<Integer>();

q.add(i);
map.put(c, q);          
i++;
}

return map;
}

static Map<Character, Queue<Integer>> copyMap(Map<Character, Queue<Integer>> mapcopy){
Map<Character, Queue<Integer>> map = new HashMap<>(mapcopy.size());
mapcopy.forEach((k,v)->{
map.put(k, new ArrayDeque<>(v));
});

return map;
}

public static void main(String[] args) {
// TODO Auto-generated method stub
Map<Character, Queue<Integer>> map = BuildMap();

List<String> dic = Arrays.asList("able", "ale");        

for(var d:dic) {
var currMap = copyMap(map);
for(var c:d.toCharArray()) {        
System.out.println(currMap.get(c).poll());
}
}
}
}

Answer 1

您可以直接迭代Map，并将每个值复制到新的Map中。

mapCopy(mapCopy mapcopy){
this.map = new HashMap<>(mapcopy.map.size());
mapcopy.map.forEach((k,v)->{
map.put(k, new ArrayDeque<>(v));
});
}