从 hashmap1 中查找 add/remove 的哪些键和值等于 hashmap2

Question

假设我有以下情况：

我想从 hashmap1 中找到 add/remove 的哪些键和值，以便 hashmap1 和 hashmap2 具有相同的值。

hashmap1: {obj2=[Brazil], obj1=[Argentina, Chile, Brazil], obj3Mobile=[Russia]}

hashmap2: {obj3Op=[Germany], obj2=[Brazil, China], obj1=[Argentina, Brazil]}

我的预期输出是：

add:  {obj2=[China], obj3Op=[Germany]}

remove: {obj3Mobile=[Russia], obj1=[Chile]}

为了重现数据集：

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.List;
import java.util.ArrayList;

public class Main
{
    public static void main(String[] args) {
        Map<String, List<String>> dictOP = new HashMap<String, List<String>>();
        Map<String, List<String>> dictMobile = new HashMap<String, List<String>>();
        
        List<String> obj1Mobile = new ArrayList<String>();
        List<String> obj2Mobile = new ArrayList<String>();
        List<String> obj3Mobile = new ArrayList<String>();
        
        List<String> obj1Op = new ArrayList<String>();
        List<String> obj2Op = new ArrayList<String>();
        List<String> obj3Op = new ArrayList<String>();
        
        
        obj1Mobile.add("Argentina");
        obj1Mobile.add("Chile");
        obj1Mobile.add("Brazil");
        obj2Mobile.add("Brazil");
        obj3Mobile.add("Russia");
        
        
        obj1Op.add("Argentina");
        obj1Op.add("Brazil");
        obj2Op.add("Brazil");
        obj2Op.add("China");
        obj3Op.add("Germany");
        
        dictOP.put("obj1", obj1Op);
        dictOP.put("obj2", obj2Op);
        dictOP.put("obj3Op", obj3Op);
        
        dictMobile.put("obj1", obj1Mobile);
        dictMobile.put("obj2", obj2Mobile);
        dictMobile.put("obj3Mobile", obj3Mobile);
        
        System.out.println(dictMobile);
        System.out.println(dictOP);
        

    }
}

使用下面的这种方法，我只能找到要添加和删除的键。

    //Union of keys from both maps
    HashSet<String> removeKey = new HashSet<>(dictMobile.keySet());
    removeKey.addAll(dictOP.keySet());
    removeKey.removeAll(dictMobile.keySet());
     
    HashSet<String> addKey = new HashSet<>(dictOP.keySet());
    addKey.addAll(dictMobile.keySet());
    addKey.removeAll(dictOP.keySet());
    
    System.out.println(removeKey);
    System.out.println(addKey);

但我找不到将键和值放在一起的简单方法

Answer 1

But I could not found a simple way to get both keys and values together

是的，您可以使用 entrySet() 方法从映射中同时获取键和值。

然后就可以这样使用了

for (var entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

Answer 2

一种方法是首先将 Map<String, List<String>> 展平为许多对。然后对其进行操作。最后将结果组合回 Map<String, List<String>>.

因此，首先，您需要编写执行展平和合并的辅助方法：

private static Set<Entry<String, String>> flatten(Map<String, List<String>> map) {
    return map.entrySet().stream().flatMap(e ->
          e.getValue().stream().map(v -> Map.entry(e.getKey(), v))
        )
        .collect(Collectors.toSet());
}

private static Map<String, List<String>> group(Set<Map.Entry<String, String>> entries) {
    return entries.stream().collect(Collectors.groupingBy(
        Map.Entry::getKey, Collectors.mapping(Map.Entry::getValue, Collectors.toList())
    ));
}

那就很直接了：

var mobileEntries = flatten(dictMobile);
var opEntries = flatten(dictOP);
var add = new HashSet<>(opEntries);
add.removeAll(mobileEntries);
var remove = new HashSet<>(mobileEntries);
remove.removeAll(opEntries);
System.out.println(group(add));
System.out.println(group(remove));

这会打印：

{obj3Op=[Germany], obj2=[China]}
{obj1=[Chile], obj3Mobile=[Russia]}

从 hashmap1 中查找 add/remove 的哪些键和值等于 hashmap2

Finding which keys and values to add/remove from hashmap1 to be equal to hashmap2

java

hashmap