stream流实现从List 集合中取出对象中相同属性的值存放到新的list集合中，返回map结构_list.stream.map返回新的对象

@RequestMapping("list2")
    @ResponseBody
    public List<Map<Long, List<PlanDO>>> getList2() {

        List<PlanDO> list = new ArrayList<>();

        list.add(new PlanDO(1l,1l,"0",new Date()));
        list.add(new PlanDO(2l,116l,"0",new Date()));
        list.add(new PlanDO(3l,118l,"0",new Date()));
        list.add(new PlanDO(6l,1l,"0",new Date()));
        list.add(new PlanDO(5l,116l,"0",new Date()));
        list.add(new PlanDO(4l,118l,"0",new Date()));
        
        Map<Long, List<PlanDO>> collect = list.stream().collect(Collectors.groupingBy(PlanDO::getUserId));
        List<Map<Long, List<PlanDO>>> maps1 = new ArrayList<>();
        maps1.add(collect);
        return maps1;
    }