Java Thread.sleep() Method

The Thread.sleep() method in Java is used to pause the execution of the currently running thread for a specified amount of time. After the sleep duration ends, the thread becomes runnable again and continues execution based on thread scheduling.

Throws InterruptedException if another thread interrupts during sleep.
Actual sleep duration may vary based on system load; higher load increases sleep time.

Java

public class SleepDemo {
    public static void main(String[] args) throws InterruptedException {
        for (int i = 0; i < 3; i++) {
            System.out.print(i + " ");
            Thread.sleep(1000);
        }
    }
}

Output:

0 1 2

Explanation:

The main thread prints numbers from 0 to 2.
After printing each number, Thread.sleep(1000) pauses the execution for 1 second.
This creates a visible delay between each printed value.

Syntax

There are 2 variations of the sleep() method in Java Thread. These are:

public static void sleep(long millis)
public static void sleep(long millis, int nanos)

Parameters:

millis: Duration of time in milliseconds for which thread will sleep
nanos: This is the additional time in nanoseconds for which we want the thread to sleep. It ranges from 0 to 999999..

Common Examples of Thread.sleep()

Example 1: Using Thread.sleep() Method for Main Thread

Java

import java.io.*;
import java.lang.Thread;

class Geeks 
{
    public static void main(String[] args)
    {
        // we use throws keyword followed by exception
      	// name for throwing the exception
        try {
            for (int i = 0; i < 5; i++) {
              
                // sleep the main thread for 1 sec
                // for every loop runs
                Thread.sleep(1000);
              
                System.out.print(i+" ");
            }
        }
        catch (Exception e) {
            // catching the exception
            System.out.println(e);
        }
    }
}

Output:

0 1 2 3 4

Explanation:

The main thread executes the loop and prints numbers from 0 to 2.
After each print, Thread.sleep(1000) pauses the current thread for 1000 milliseconds (1 second).
The thread resumes execution after the sleep duration expires.

Example 2: Using Thread.sleep() method for Custom thread

Java

import java.lang.Thread;

// Class extending the Thread Class
class MyThread extends Thread 
{
    // Overriding the run method
    @Override
    public void run()
    {
        // use throws keyword followed by exception
      	// name for throwing the exception
        try {
            for (int i = 0; i < 5; i++) {
              
                // method will sleep the thread
                Thread.sleep(1000);
              
                System.out.print(i+" ");
            }
        }
        catch (Exception e) {
            // catching the exception
            System.out.println(e);
        }
    }

    public static void main(String[] args)
    {
        // created thread
        MyThread obj = new MyThread();
        obj.start();
    }
}

Output:

0 1 2 3 4

Explanation:

MyThread extends the Thread class and overrides the run() method.
The run() method prints numbers from 0 to 4.
Thread.sleep(1000) pauses the execution of the custom thread for 1 second in each iteration.
The sleep() call is placed inside a try-catch block to handle InterruptedException.
The thread resumes execution after each sleep cycle.

Example 3: IllegalArguementException when sleep time is Negative

Java

import java.lang.Thread;

class Geeks 
{
    public static void main(String[] args)
    {
        // Use throws keyword followed by exception
      	// name for throwing the exception
        try {
            for (int i = 0; i < 5; i++) {
              
                // this will throw the
                // IllegalArgumentException
                Thread.sleep(-100);
              
                // Printing the value of the variable
                System.out.println(i);
            }
        }
        catch (Exception e) {
            // Catching the exception
            System.out.println(e);
        }
    }
}

Output

java.lang.IllegalArgumentException: timeout value is negative

Explanation:

Passing a negative value to Thread.sleep() is invalid.
Java throws an IllegalArgumentException immediately.
This ensures that sleep duration is always non-negative.

Java Thread.sleep() Method

Syntax

Common Examples of Thread.sleep()

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