前言

有时我们需要定期执行某个程序，比如隔一段时间备份一下日志文件，查询或者更新某个数据等等，这时就需要写一个定时执行的功能。

一、定期执行

如何让每周日18:00:00定时执行任务？

    @Test
    public void testLocalDateTime() {
    
    
        //获取当前时间
        LocalDateTime now = LocalDateTime.now();
        //获取本周四 18:00:00:000
        LocalDateTime thursday  = now.with(DayOfWeek.THURSDAY).withHour(18).withMinute(0).withSecond(0).withNano(0);
        if(now.compareTo(thursday) >=0){
    
    
            thursday = thursday.plusWeeks(1);
        }
        //计算时间差，即延时执行时间
        long initialDelay = Duration.between(now, thursday).toMillis();
        //计算每次执行的间隔时间，即一周的毫秒值
        long oneWeek = 7 * 24 * 60 * 60 * 1000;
        ScheduledExecutorService executorService = Executors.newScheduledThreadPool(2);
        System.out.println("开始时间："+new Date());
        executorService.scheduleAtFixedRate(() -> {
    
    
            System.out.println("执行时间：" + new Date());
        },initialDelay,oneWeek, TimeUnit.MILLISECONDS);

    }