Trying to call a function every 24 hours

Question

I'm trying to get a function to be called every day. Right now my code is as follows:

do {
    Thread.sleep(1000*60*60*24);
    readInFile();
} while (true);

The issue is that it is being called every day plus the time it takes to execute the function readInFile. Is there a way to do a callback or something to go off every 24 hours?

Schedule an application to execute periodically using the host task scheduling system. (Such as `cron` or Windows Task Scheduler for example.) Sleeping a thread for 24 hours is generally a bad idea. — David, Oct 13 '15 at 14:46
You could calculate the time it next needs to run. Then sleep for something like a minute and compare the current time with the calculated time. — Jan Henke, Oct 13 '15 at 14:46
If it has to be pure Java, I would look into Executors.newScheduledThreadPool. Create your pool with a size of one and give it a Runnable that runs your readInFile() method. — jgitter, Oct 13 '15 at 14:47
You could also use another thread to execute the function, keeping this one active. — Dean Meehan, Oct 13 '15 at 14:47
Or creep up on it by sleeping for 12 hours, 6, 3 and so on down to a second,say, recalculating the ms of sleep time remaining using the real-time clock. — Martin James, Oct 13 '15 at 14:48

score 7 · Answer 1 · answered Oct 13 '15 at 14:48

You can use ScheduledExecutorService.scheduleAtFixedRate method to invoke a Runnable at a fixed rate.

Sample code to invoke a runnable every day (with no initial delay):

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(myRunnable, 0, 1, TimeUnit.DAYS);

Rahul Tripathi · Accepted Answer · 2015-10-13T14:51:37.090

5

You can try this:

Timer timer = new Timer ();
TimerTask t = new TimerTask () {
    @Override
    public void run () {
        // some code
    }
};

timer.schedule (t, 0l, 1000*60*60*24);

or else you can use the ScheduledExecutorService

An ExecutorService that can schedule commands to run after a given delay, or to execute periodically.

edited Oct 13 '15 at 14:51

answered Oct 13 '15 at 14:47

Rahul Tripathi

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That is not going to be any better than sleep calls. – Martin James Oct 13 '15 at 14:49
`s/schedule/scheduleAtFixedRate/` – zapl Oct 13 '15 at 14:51
@MartinJames:- Hmm..ScheduledExecutorService will do the trick. Tunaki has hit it. – Rahul Tripathi Oct 13 '15 at 14:53
1

`Timer`/`TimerTask` can do the right thing too but you need to use one of the "AtFixedRate" versions: https://docs.oracle.com/javase/8/docs/api/java/util/Timer.html#scheduleAtFixedRate-java.util.TimerTask-long-long- what you do is "for repeated fixed-delay execution" which has the same problem as a fixed sleep. – zapl Oct 13 '15 at 14:55

Ann Addicks · Answer 3 · 2015-10-13T15:02:13.583

You can use a scheduler such as Quartz or Spring to set the code to be run once per day.

Spring http://docs.spring.io/spring/docs/current/spring-framework-reference/html/scheduling.html

http://spring.io/guides/gs/scheduling-tasks/

//1:01 am every day
@Scheduled(cron = "0 1 1 * * ?")
public void readDaily() {
  readInFile();
}

Quartz https://quartz-scheduler.org

JobDetail job = new JobDetail();
    job.setName("dummyJobName");
    job.setJobClass(HelloJob.class);

    //configure the scheduler time
    Trigger trigger = new CronTrigger("trigger1", "group1");
    trigger.setCronExpression("0 0 15 * * ?"); //3pm every day

    //schedule it
    Scheduler scheduler = new StdSchedulerFactory().getScheduler();
    scheduler.start();
    scheduler.scheduleJob(job, trigger);

Trying to call a function every 24 hours

3 Answers3

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