How To Use Thread.sleep() in Java with Examples

The Thread.sleep() method in Java is used to pause the execution of the current thread for a specific amount of time (in milliseconds). This is useful when you want to delay program execution, control thread scheduling, or simulate real-time processing.

Syntax of Thread.sleep()

Thread.sleep(milliseconds);
Thread.sleep(milliseconds, nanoseconds);

• milliseconds – time in milliseconds to pause execution.
• nanoseconds – optional additional time in nanoseconds.

Example 1: Basic Usage of Thread.sleep()

public class SleepExample {
    public static void main(String[] args) {
        System.out.println("Program starts...");
        try {
            Thread.sleep(2000); // pause for 2 seconds
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Program resumes after 2 seconds.");
    }
}

Output:

Program starts...
(2-second pause)
Program resumes after 2 seconds.

Example 2: Using Thread.sleep() in a Loop

public class LoopSleepExample {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            System.out.println("Count: " + i);
            try {
                Thread.sleep(1000); // pause for 1 second each iteration
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

This example pauses the program for one second between each count.

Example 3: Handling InterruptedException

The Thread.sleep() method throws an InterruptedException, which must be handled using try-catch.

public class InterruptedExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> {
            try {
                System.out.println("Thread going to sleep...");
                Thread.sleep(3000);
                System.out.println("Thread woke up!");
            } catch (InterruptedException e) {
                System.out.println("Thread was interrupted!");
            }
        });

        thread.start();
        thread.interrupt(); // interrupt before completion
    }
}

Important Notes

• Thread.sleep() does not release any locks while sleeping.
• Always handle InterruptedException properly in multi-threaded applications.
• Do not use Thread.sleep() for precise timing in production; use ScheduledExecutorService instead.

Conclusion

The Thread.sleep() method is a simple way to pause execution in Java. It is most commonly used for simulating delays, controlling program flow, or testing multi-threaded behavior. With proper exception handling, it can be an effective tool for Java developers.