list中map将根据某几个key值相等的累加

直接上代码，可直接运行：

public static void main(String[] args) {
        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
        Map<String, Object> map1 = new HashMap<String, Object>();
        map1.put("id", 1);
        map1.put("date", 20190425);
        map1.put("value", 2);
        list.add(map1);

        Map<String, Object> map2 = new HashMap<String, Object>();
        map2.put("id", 1);
        map2.put("date", 20190425);
        map2.put("value", 5);
        list.add(map2);

        Map<String, Object> map3 = new HashMap<String, Object>();
        map3.put("id", 2);
        map3.put("date", 20190425);
        map3.put("value", 5);
        list.add(map3);

        Map<String, Object> map4 = new HashMap<String, Object>();
        map4.put("id", 2);
        map4.put("date", 20190425);
        map4.put("value", 4);
        list.add(map4);

        Map<String, Object> map5 = new HashMap<String, Object>();
        map5.put("id", 1);
        map5.put("date", 20190424);
        map5.put("value", 4);
        list.add(map5);

        //id相等value相加（合并id相同数据）
        System.out.println("原始数据："+list);
        //方法二
        Map<String, Map<String, Object>> result = new HashMap<String, Map<String,Object>>();
        List<Map<String, Object>>  allList = new ArrayList<>();
        for(Map<String, Object> map : list){
            String id = map.get("id").toString();
            String date = map.get("date").toString();
            String newId  = id+date;
            Long value = Long.parseLong(map.get("value").toString());
            if(result.containsKey(newId)){
                Long temp = Long.parseLong(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("合并后的数据2："+allList);
    }

根据date和id相等的key相加求和，效果如下：