Java 1초마다 반복, 실행

어떤 내용을 1초마다 반복, 실행하는 방법입니다.

1. Thread.sleep()

Thread.sleep()은 인자로 전달된 milliseconds 만큼 지연을 시킵니다.

아래와 같이 for문에서 sleep()을 사용하여 1초 간격으로 어떤 내용을 반복시킬 수 있습니다.

import java.time.LocalDateTime;

public class Example {

    public static void main(String[] args) {

        for (int i = 0; i < 10; i++) {
            // do something
            System.out.println("Repeat something a second: " + LocalDateTime.now());

            // sleep 1 sec
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

Output:

Repeat something a second: 2022-12-18T06:47:05.931674862
Repeat something a second: 2022-12-18T06:47:06.939187953
Repeat something a second: 2022-12-18T06:47:07.939633919
Repeat something a second: 2022-12-18T06:47:08.940085243
Repeat something a second: 2022-12-18T06:47:09.940596444
Repeat something a second: 2022-12-18T06:47:10.941064544
Repeat something a second: 2022-12-18T06:47:11.941521652
Repeat something a second: 2022-12-18T06:47:12.941997104
Repeat something a second: 2022-12-18T06:47:13.942430146
Repeat something a second: 2022-12-18T06:47:14.942996023

2. TimeUnit.SECONDS.sleep()

TimeUnit.SECONDS.sleep(n)는 n초만큼 지연시킵니다.

아래와 같이 for문에서 1초 간격으로 어떤 내용을 실행시킬 수 있습니다.

import java.time.LocalDateTime;
import java.util.concurrent.TimeUnit;

public class Example {

    public static void main(String[] args) {

        for (int i = 0; i < 10; i++) {
            // do something
            System.out.println("Repeat something a second: " + LocalDateTime.now());

            // sleep 1 sec
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

Output:

Repeat something a second: 2022-12-18T06:48:27.660873910
Repeat something a second: 2022-12-18T06:48:28.667687578
Repeat something a second: 2022-12-18T06:48:29.668084259
Repeat something a second: 2022-12-18T06:48:30.668541468
Repeat something a second: 2022-12-18T06:48:31.669024824
Repeat something a second: 2022-12-18T06:48:32.669485696
Repeat something a second: 2022-12-18T06:48:33.669843649
Repeat something a second: 2022-12-18T06:48:34.670223852
Repeat something a second: 2022-12-18T06:48:35.670655551
Repeat something a second: 2022-12-18T06:48:36.671162759

3. Timer

Timer를 이용하여 어떤 내용을 주기적으로 반복 시킬 수 있습니다.

Timer.scheduleAtFixedRate(TimerTask, delay, period)는 TimerTask의 작업 내용을 period 간격으로 실행시킵니다. delay는 첫번째 작업을 실행할 때 지연시키는 시간입니다.

Timer.cancel()로 주기적인 작업을 종료시킬 수 있습니다. 일정시간이 지난 뒤에 호출하시면 종료되며, cancel()을 호출하지 않으면 무한히 반복 실행됩니다.

import java.time.LocalDateTime;
import java.util.Timer;
import java.util.TimerTask;

public class Example {

    public static void main(String[] args) {
        TimerTask task = new TimerTask() {
            public void run() {
                System.out.println("Repeat something a second: " + LocalDateTime.now());
            }
        };
        Timer timer = new Timer("Timer");
        long delay = 0;
        long period = 1000;
        timer.scheduleAtFixedRate(task, delay, period);

        // sleep 10 seconds
        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("Cancel the timer");
        timer.cancel();
    }
}

Output:

Repeat something a second: 2022-12-18T06:53:50.734644869
Repeat something a second: 2022-12-18T06:53:51.714507059
Repeat something a second: 2022-12-18T06:53:52.714876200
Repeat something a second: 2022-12-18T06:53:53.714251911
Repeat something a second: 2022-12-18T06:53:54.714715381
Repeat something a second: 2022-12-18T06:53:55.715040314
Repeat something a second: 2022-12-18T06:53:56.714356582
Repeat something a second: 2022-12-18T06:53:57.714837762
Repeat something a second: 2022-12-18T06:53:58.714232157
Repeat something a second: 2022-12-18T06:53:59.714480444
Cancel the timer