Difference between Wait and Sleep in Java

Introduction to Wait() method

Java's wait() function is used to put a thread's execution on hold until it hears from another thread. This technique, which is used to synchronize threads, is independent of time. A thread enters the waiting state and releases the lock on the object it is presently holding when it invokes the wait() function. Other threads are now able to access the locked object and execute their own commands.

Let's discuss some important points regarding the Wait() method:

• Used to hold up a thread's progress until it receives a message from another thread.
• After releasing the lock, the thread moves into the waiting state.
• It can be woken up by another thread using the notify() or notifyAll() methods.
• If the thread is interrupted while waiting, it throws an InterruptedException.

Syntax

try{
	// Acquiring lock
	synchronized(object){
		// Calling wait() on the object
		object.wait();
	}
}
catch(InterruptedException e){
	// Exception handling
}

Example

Let's discuss an example to understand better.

Code

class WaitExample{
	public static void main(String[] args) throws InterruptedException{
		final Object lock = new Object();
		System.out.println("Acquiring lock...");
		synchronized(lock){
			System.out.println("Lock acquired...");
			lock.wait();
			System.out.println("Lock released...");
		}
	}
}

Output

Explanation

The wait() method is used in this example to release the lock on an object while anticipating a notification from another thread. To print "Lock released...", the program first acquires the lock, uses lock.wait() to release it, and then waits for another thread to provide notice. If the thread is interrupted while waiting, the InterruptedException is thrown.

Sleep() Vs Wait()

Java offers two functions that can be used to suspend a thread's execution: wait() and sleep(). In the following sections, we will know more about the differences between these two methods.

Must Read Static Blocks In Java.

Frequently Asked Questions

Can we call the wait() method without acquiring a lock on the object?

No, calling the wait() method requires the thread to acquire the lock on the object.

Can we interrupt a thread while it is sleeping using the sleep() method?

Yes, we can interrupt a thread while it is sleeping utilizing the interrupt() method.

Can the sleep() method be used to wait for a notification from another thread?

No, the sleep() method is time-dependent and does not require any notification to proceed with the execution.

How can we wake up a thread waiting using the wait() method?

We can wake up a thread waiting using the notify() or notifyAll() method.

Can we use the wait() and sleep() methods together?

Yes, using the wait() and sleep() methods together is possible, but it depends on the use case.

Conclusion

In conclusion, the sleep() and wait() methods are two crucial Java techniques for thread synchronization. Despite their apparent similarity, the two approaches differ significantly from one another. While the sleep() function is time-dependent and doesn't need any notice, the wait() method is time-independent and requires notification from another thread. To create Java code that is effective and synchronized, it is essential to comprehend these distinctions. 

So it's time for you now to refer to other articles based on a similar topic:

• Sleep() method
• Thread Synchronization
• Multithreading in Java
• Difference Between IOT and M2M
   

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