How to add delay in Java using sleep method?

General Discussions
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1

What is the best way to introduce a delay in Java using the sleep method?

I’m building a step sequencer in Java and need to introduce a delay between iterations in a while loop. For example, I want to pause execution at certain points before proceeding to the next step. How can I achieve this using sleep Java, and what is the best way to implement it correctly?

2

Ah, the good old Thread.sleep()! If you just need a simple pause, this does the job.

while (true) {
    ceva[i].setSelected(true);
    
    try {
        Thread.sleep(1000); // Pause for 1 second
    } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
    }

    ceva[i].setSelected(false);

    try {
        Thread.sleep(1000);
    } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
    }

    i = (i + 1) % ceva.length;
}

:white_check_mark: Why use this?

  • Super simple & effective for basic delays.
  • Works well for sequential logic where blocking the thread is okay.

:rotating_light: Be careful!

  • Thread.sleep() blocks the current thread, making it a poor choice for UI applications.

:arrow_down: But what if you don’t want to block the main thread? Enter ScheduledExecutorService…

3

If you want more control & don’t want to block your main thread, ScheduledExecutorService is your friend.

import java.util.concurrent.*;

public class StepSequencer {
    private static final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
    
    public static void main(String[] args) {
        Runnable stepTask = new Runnable() {
            private int i = 0;

            @Override
            public void run() {
                ceva[i].setSelected(true);

                scheduler.schedule(() -> ceva[i].setSelected(false), 1, TimeUnit.SECONDS);

                i = (i + 1) % ceva.length;
                scheduler.schedule(this, 2, TimeUnit.SECONDS);
            }
        };

        scheduler.schedule(stepTask, 0, TimeUnit.SECONDS);
    }
}

:white_check_mark: Why use this?

  • Non-blocking – lets the main thread remain free.
  • More control over scheduling.

:rotating_light: Best for:

  • Multi-threaded apps.
  • Running tasks in the background without freezing UI.
4

For repeating tasks, Timer + TimerTask works well.

import java.util.Timer;
import java.util.TimerTask;

public class StepSequencer {
    public static void main(String[] args) {
        Timer timer = new Timer();
        timer.scheduleAtFixedRate(new TimerTask() {
            private int i = 0;

            @Override
            public void run() {
                ceva[i].setSelected(true);

                new Timer().schedule(new TimerTask() {
                    @Override
                    public void run() {
                        ceva[i].setSelected(false);
                    }
                }, 1000); // Delay deselecting by 1 second

                i = (i + 1) % ceva.length;
            }
        }, 0, 2000);
    }
}

:white_check_mark: Why use this?

  • Easy to set up periodic execution.
  • Great for animations, repeated sequences, or scheduled jobs.

:rotating_light: Downsides?

  • Less flexible than ScheduledExecutorService.
  • Not ideal for complex, dynamic tasks.