Java List＜Map＞集合根据相同key分组进行某项数据求和

Posted 2022-12-03 java李杨勇

 

package com.yt.exam.ctrl;

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

/**
 * Created by LiYangYong 
 */
public class test 
    public static void main(String[] args) 
        List<Map<String, Object>> list = new ArrayList<>();
        Map<String, Object> map1 = new HashMap<>();
        map1.put("userId", "120");
        map1.put("value", 111);
        list.add(map1);

        Map<String, Object> map2 = new HashMap<>();
        map2.put("userId", "120");
        map2.put("value", 112);
        list.add(map2);

        Map<String, Object> map3 = new HashMap<>();
        map3.put("userId", "110");
        map3.put("value", 2022);
        list.add(map3);

        Map<String, Object> map4 = new HashMap<>();
        map4.put("userId", "110");
        map4.put("value", 56);
        list.add(map4);


        Map<String, Object> map5 = new HashMap<>();
        map5.put("userId", "159");
        map5.put("value", 2022);
        list.add(map5);

        System.out.println("统计后的数据--->>>"+list);
        //根据userId key 合计value
        Map<String, Map<String, Object>> result = new HashMap<>();
        List<Map<String, Object>>  allList = new ArrayList<>();
        for(Map<String, Object> map : list)
            String newId = map.get("userId").toString();
            Integer value = Integer.parseInt(map.get("value").toString());
            if(result.containsKey(newId))
                Integer temp = Integer.parseInt(result.get(newId).get("value").toString());
                value += temp;
                result.get(newId).put("value", value);
                continue;
            
            result.put(newId, map);
            allList.add(map);
        
        System.out.println("");
        System.out.println("统计后的数据--->>>"+allList);
    

测试结果如下：