案例

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import java.util.*;
import java.util.stream.Collectors;
 
public class Test {
 
    public static void main(String[] args) {
        //list模拟数据
        Map map1 = new HashMap();
        map1.put("shopId",1);
        map1.put("salesmanId",2);
        map1.put("money", 20);
 
        Map map2 = new HashMap();
        map2.put("shopId",2);
        map2.put("salesmanId",2);
        map2.put("money", 100);
 
        Map map5 = new HashMap();
        map5.put("shopId",2);
        map5.put("salesmanId",2);
        map5.put("money", 50);
 
        List<Map> list1 = new ArrayList<>();
        list1.add(map1);
        list1.add(map2);
        list1.add(map5);
//        System.out.println(list1);
//        [{salesmanId=2, money=20, shopId=1}, {salesmanId=2, money=100, shopId=2}, {salesmanId=2, money=50, shopId=2}]
 
        //list<Map>分组，按超市分组
        // Map<String, List<ShopEntity>> mapGroup = list1.stream().collect(Collectors.groupingBy(ShopEntity::getShopId));
        Map<String, List<Map>> mapGroup = list1.stream().collect(Collectors.groupingBy(o -> o.get("shopId") + ""));
//        System.out.println(mapGroup);
//        {1=[{salesmanId=2, money=20, shopId=1}], 2=[{salesmanId=2, money=100, shopId=2}, {salesmanId=2, money=50, shopId=2}]}
        List<Map> listReturn = new ArrayList<>();
        for (String str : mapGroup.keySet()) {
            List<Map> task1 = mapGroup.get(str);
            int money = 0;
            for (Map mm: task1) {
                money = money + Integer.valueOf(String.valueOf(mm.get("money")));
            }
            Map<String, Object> mapReturn = new HashMap();
            mapReturn.put("shopId", task1.get(0).get("shopId"));
            mapReturn.put("salesmanId", task1.get(0).get("salesmanId"));
            mapReturn.put("money", money);
            listReturn.add(mapReturn);
        }
//        System.out.println(listReturn);
//        [{salesmanId=2, money=20, shopId=1}, {salesmanId=2, money=150, shopId=2}]
 
        //根据money 倒叙排序
        Collections.sort(listReturn, (o2, o1) -> {
            Integer shop1 = Integer.valueOf(o1.get("shopId").toString());
            Integer shop2 = Integer.valueOf(o2.get("shopId").toString());
            return shop1.compareTo(shop2);
        });
//        System.out.println(listReturn);
//        [{salesmanId=2, money=150, shopId=2}, {salesmanId=2, money=20, shopId=1}]
    }
}