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This tutorial explains how to create program delays in Java and gives some sample code to understand it.

There are several ways to create a time delay, such as TimeUnit.sleep(),, ScheduleAtFixedRate()etc. Thread.sleep()Let's look at an example.

Thread.sleep()Creating delays using methods in Java

ThreadIs a Java class used to create and execute tasks concurrently, and provides a sleep()method to pause the current execution for a period of time.

public class SimpleTesting {
  public static void main(String[] args) {
    try {
      for (int i = 0; i < 2; i++) {
        Thread.sleep(1000);
        System.out.println("Sleep " + i);
      }
    } catch (Exception e) {
      System.out.println(e);
    }
  }
}

Output:

Sleep 0
Sleep 1

TimeUnit.sleep()Delaying with method in Java

In this example, we use the method TimeUnitof the class sleep()to delay the execution for a specified time. TimeUnitThe class belongs to a concurrent API package in Java.

import java.util.concurrent.TimeUnit;

public class SimpleTesting {
  public static void main(String[] args) {
    try {
      for (int i = 0; i < 2; i++) {
        TimeUnit.SECONDS.sleep(2);
        System.out.println("Sleep " + i);
      }
    } catch (Exception e) {
      System.out.println(e);
    }
  }
}

Output:

Sleep 0
Sleep 1

ScheduledExecutorServiceDelaying in Java using

Java provides a class ScheduledExecutorServiceto schedule execution in a concurrent environment. We can use its run()methods to execute separate execution paths. See the following example.

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class Main {
  public static void main(String args[]) {
    try {
      final ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
      executorService.scheduleAtFixedRate(new Runnable() {
        @Override
        public void run() {
          executeTask();
        }
      }, 0, 1, TimeUnit.SECONDS);
    } catch (Exception e) {
      System.out.println(e);
    }
  }
  private static void executeTask() {
    System.out.println("Task Executing... ");
  }
}

Output:

Task Executing... 
Task Executing... 
Task Executing... 

ScheduledExecutorServiceDelaying in Java using

If you are using Java 9 or higher, you can use the concept of method reference scheduleAtFixedRate()to call methods from within a method. See the following example.

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class SimpleTesting {
  public static void main(String[] args) {
    try {
      final ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
      executorService.scheduleAtFixedRate(SimpleTesting::executeTask, 1, 2, TimeUnit.SECONDS);
    } catch (Exception e) {
      System.out.println(e);
    }
  }
  private static void executeTask() {
    System.out.println("Task Executing... ");
  }
}

Output:

Task Executing... 
Task Executing... 
Task Executing...