Java Thread.sleep() Method

Thread class contains the sleep() method. There are two overloaded methods of sleep() present in the Thread Class: one with one argument and another with two arguments. The sleep() method is used to pause the execution of the current thread for a specific duration, after which the thread resumes execution.

Syntax

There are two variations of the sleep() method in Java Thread:

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

Parameters

• millis: Duration of time in milliseconds for which the thread will sleep.
• nanos: Additional time in nanoseconds (range: 0 to 999999).

Exceptions

• InterruptedException
• IllegalArgumentException

Important Points

• Thread.sleep() pauses the current thread’s execution.
• Throws InterruptedException if another thread interrupts during sleep.
• Actual sleep duration may vary based on system load.
• Can be used for both main thread and custom threads.

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

import java.io.*;
import java.lang.Thread;
 
class Coding75 {
    public static void main(String[] args) {
        try {
            for (int i = 0; i < 5; i++) {
                Thread.sleep(1000); // Sleep for 1 second
                System.out.print(i + " ");
            }
        } catch (Exception e) {
            System.out.println(e);
        }
    }
}

Output

0 1 2 3 4

Example 2: Using Thread.sleep() for a Custom Thread

import java.lang.Thread;
 
class MyThread extends Thread {
    @Override
    public void run() {
        try {
            for (int i = 0; i < 5; i++) {
                Thread.sleep(1000);
                System.out.print(i + " ");
            }
        } catch (Exception e) {
            System.out.println(e);
        }
    }
 
    public static void main(String[] args) {
        MyThread obj = new MyThread();
        obj.start();
    }
}

Output

0 1 2 3 4

Example 3: IllegalArgumentException When Sleep Time is Negative

import java.lang.Thread;
 
class Coding75 {
    public static void main(String[] args) {
        try {
            for (int i = 0; i < 5; i++) {
                Thread.sleep(-100); // This will throw IllegalArgumentException
                System.out.println(i);
            }
        } catch (Exception e) {
            System.out.println(e);
        }
    }
}

Output

java.lang.IllegalArgumentException: timeout value is negative

Additional Notes

• The sleep() method with one parameter is a native method, meaning its implementation is done in another programming language.
• The method with two parameters is implemented in Java.
• Both sleep() methods are static and should be accessed using the Thread class.
• Since both methods throw checked exceptions, exception handling is mandatory (using throws or try-catch).