Sleep vs Wait

In Java, sleep and wait are both used to pause the execution of a thread, but they serve different purposes and have different behaviors:

Thread.sleep(milliseconds)

• Purpose: Pauses the current thread for a specified number of milliseconds.
• Usage: Thread.sleep(1000); (Pauses for 1 second)
• Synchronization: It does not release the lock on any synchronized object.
• Waking Up: The thread resumes automatically after the specified time has passed or if it’s interrupted.
• Static Method: Belongs to the Thread class, so it directly affects the current thread.

Object.wait(milliseconds)

• Purpose: Makes the current thread wait until another thread calls notify() or notifyAll() on the same object.
• Usage: Must be called inside a synchronized block/method. For example:

synchronized(lock) {
    lock.wait();
}        

• Synchronization: It releases the lock on the object it is waiting on, allowing other threads to access the synchronized block or method.
• Waking Up: The thread resumes when notify() or notifyAll() is called on the same object, or if the optional timeout has passed.
• Non-static Method: Belongs to the Object class, so it’s invoked on a specific object.

sleep is typically used to introduce delays, while wait is essential for thread coordination in scenarios where threads need to communicate and wait for specific conditions.