Use ScheduledExecutorService to run code at specific Date time only once

Question

I have a code that has to be executed at a certain date time in the future, let's say that I have a future date and I want to execute a peace of code in that date +1 minute in the future, but only once. I know I to do this with a java Timer and TimerTask .For example doing something like this:

import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

public class Main {

    public static void main(String[] args) {

        Calendar myDate = Calendar.getInstance();
        myDate.add(Calendar.MINUTE, 1);
        Date afterOneMinute = myDate.getTime();
        System.out.println("Scheduled at:" + afterOneMinute);
        Timer timer = new Timer();

        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                System.out.println("Executed at:" + (new Date()));

            }
        }, afterOneMinute);
    }

}

I'm looking for an elegant way to to the same using ScheduledExecutorService, in order to have a specific pool, because this pool will be used for multiple calls. Does somebody can help me?

No problems at all, I want just to do the same thing in a different way (using ScheduledExecutorService), because I would like to use the pool in order to restrict the number of calls with a pool — navy1978, Jun 17 '18 at 15:49
So, read the javadoc of ScheduledExecutorService, and try something based on what you learn from reading the documentation. — JB Nizet, Jun 17 '18 at 15:50
I have already done it , thank you, but I cannot find a way to execute it only once! It is written in my question! — navy1978, Jun 17 '18 at 15:51
Possible duplicate of [How to run certain task every day at a particular time using ScheduledExecutorService?](https://stackoverflow.com/questions/20387881/how-to-run-certain-task-every-day-at-a-particular-time-using-scheduledexecutorse) — Jacob G., Jun 17 '18 at 15:53
Well, https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ScheduledExecutorService.html#schedule-java.lang.Runnable-long-java.util.concurrent.TimeUnit- says: Creates and executes a **one-shot** action that becomes enabled after the given delay. And even if you're still unsure after reading that, you can always try. — JB Nizet, Jun 17 '18 at 15:57
Ok As explained in a comment below I didn't see it, and I was expecting to find a Date in the parameters of the methods, and in any case I was looking in the ScheduleAtFixedRate and there I could not find a one-shot execution... In any case I come here and I lost time to write a question, I don't thing your answers helped a lot... At least not the first 2, in any case Thank you... — navy1978, Jun 17 '18 at 16:04
@navy1978 when I told you to read the javadoc, I meant it. Not just vaguely look at it, and make incorrect assumptions. **read** it. There are 4 methods, and the two first ones do what you want to do. It's not that hard. Don't blame me for not correctly reading the javadoc, and for not doing it when I tell you to do it. — JB Nizet, Jun 17 '18 at 16:10
I’m appreciating your explanation, but I really hate the answers like “read the doc”, it would be a lot better something like: “did you see this method in the java doc” ... the conversation started in a wrong way to my opinion, but I thank you again for your replies... — navy1978, Jun 17 '18 at 16:14

azro · Answer 1 · 2018-06-17T16:01:53.723

You can get an ScheduledExecutorService from Executors, get a SingleThread version or a MultipleThread Executors.newSingleThreadScheduledExecutor
Then provide the runnable, the duration and its TimeUnit : ScheduledExecutorService.schedule(Runnable command, long delay, TimeUnit unit)

If you want to set a duration :

ScheduledExecutorService exe = Executors.newSingleThreadScheduledExecutor();
// or Executors.newScheduledThreadPool(2); if you have multiple tasks
exe.schedule(() -> System.out.println("Executed at:" + (new Date())), 1, TimeUnit.MINUTES);

If you want to use a LocalDateTime :

ScheduledExecutorService exe = Executors.newSingleThreadScheduledExecutor();
// or Executors.newScheduledThreadPool(2); if you have multiple tasks
LocalDateTime date = LocalDateTime.of(2018, 6, 17, 18, 30, 0);
exe.schedule(
       () -> System.out.println("Executed at:" + (new Date())),
       LocalDateTime.now().until(date, ChronoUnit.MINUTES),
       TimeUnit.MINUTES);

score 2 · Accepted Answer · answered Jun 17 '18 at 15:52

2

You can use ScheduledExecutorService.schedule(Runnable command, long delay, TimeUnit unit)

long delay = afterOneMinute.getTime() - System.currentTimeMillis();
ScheduledExecutorService executorService = ...;
executorService.schedule(runnable, delay, TimeUnit.MILLISECONDS);

answered Jun 17 '18 at 15:52

xingbin

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I saw somebody gave you a down vote and I gave you an up one, because I think it's the correct way to do it, I could not find the schedule method in the JavaDoc that takes a Date as a parameters and I didn't see this without a period. I will accept your question, because it's what I need... Thank. you – navy1978 Jun 17 '18 at 16:01
2

I have the impression that some of the guys here love to give down votes... – navy1978 Jun 17 '18 at 16:02

Use ScheduledExecutorService to run code at specific Date time only once

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