CODEWITHSUNDEEP
javascheduled-tasksrunnableexecutor
Ray
Ray

Reputation: 4879

Schedule Java task for a specified time

I would like to be able to schedule a task at a specific time in Java. I understand that the ExecutorService has the ability to schedule at periodic intervals, and after a specified delay, but I am looking more for a time of day as opposed to after a duration.

Is there a way to have, say, a Runnable execute at 2:00, or do I need to calculate the time between now and 2:00, and then schedule the runnable to execute after that delay?

Upvotes: 6

Views: 14480

Answers (6)

Victor
Victor

Reputation: 3698

Got myself on this situation this morning... This was my code to run at midnight

    scheduler = Executors.newScheduledThreadPool(1);
    Long midnight=LocalDateTime.now().until(LocalDate.now().plusDays(1).atStartOfDay(), ChronoUnit.MINUTES);
    scheduler.scheduleAtFixedRate(this, midnight, 1440,  TimeUnit.MINUTES);

Upvotes: 2

theme
theme

Reputation: 361

this is how I've solved it using java7SE:

    timer = new Timer("Timer", true);
    Calendar cr = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
    cr.setTimeInMillis(System.currentTimeMillis());
    long day = TimeUnit.DAYS.toMillis(1);
    //Pay attention - Calendar.HOUR_OF_DAY for 24h day model 
    //(Calendar.HOUR is 12h model, with p.m. a.m. )
    cr.set(Calendar.HOUR_OF_DAY, it.getHours());
    cr.set(Calendar.MINUTE, it.getMinutes());
    long delay = cr.getTimeInMillis() - System.currentTimeMillis();
    //insurance for case then time of task is before time of schedule
    long adjustedDelay = (delay > 0 ? delay : day + delay);
    timer.scheduleAtFixedRate(new StartReportTimerTask(it), adjustedDelay, day);
    //you can use this schedule instead is sure your time is after current time
    //timer.scheduleAtFixedRate(new StartReportTimerTask(it), cr.getTime(), day);

it happens to be trickier than I thought to do it correctly

Upvotes: 6

Peter Szanto
Peter Szanto

Reputation: 7722

you can use spring annotations too

@Scheduled(cron="*/5 * * * * MON-FRI")
public void doSomething() {
// something that should execute on weekdays only
}

http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/scheduling.html

Upvotes: 7

AlexR
AlexR

Reputation: 115398

user java.util.Timer. It has method new schedule(task, time) where time is a Date when you want to execute the task once.

Upvotes: 0

Polynomial
Polynomial

Reputation: 28346

Check out Quartz. We use it for our production apps, and it's very good. It works pretty much like crontab. You can specify a time during a set schedule and it'll execute a callback at that time.

Upvotes: 0

Duncan McGregor
Duncan McGregor

Reputation: 18177

You'll be wanting Quartz.

Upvotes: 4

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