Stream流遇到的问题（持续更新）

按照任务开始时间（结束时间）排序，如果开始时间（结束时间）为null，就按照结束时间（开始时间）排序

@Test
    void contextDemo(){
        long start = System.currentTimeMillis();
        QueryWrapper queryWrapper = new QueryWrapper<>();
        List times = timeMapper.selectList(queryWrapper);
        System.out.println(times);
        
        List collect = times.stream().
                sorted(Comparator.comparing(Time::getStartTime, Comparator.nullsFirst(Date::compareTo))
                .thenComparing(Time::getEndTime, Comparator.nullsFirst(Date::compareTo))
        ).collect(Collectors.toList());


        long end = System.currentTimeMillis();
        System.out.println(end-start);
        for (Time time : collect) {
            System.out.println(time);
        }
    }

 
    @Test
    void context(){
        ArrayList list = new ArrayList<>();
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 2; j++) {
                User user = new User();
                user.setId(j);
                user.setName("你好");
                list.add(user);
            }
        }
        //去重前
        System.out.println(list);
        List collectId = list.stream().filter(distinct(User::getId)).collect(Collectors.toList());
        //id去重后
        System.out.println(collectId);
        List collectName = list.stream().filter(distinct(User::getName)).collect(Collectors.toList());
        //name去重后
        System.out.println(collectName);
    }
    //移除相同值
    public static  Predicate distinct(Function keyExtractor) {
        Map concurrentHashMap = new ConcurrentHashMap<>();
        return t -> concurrentHashMap.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
    }