What is the purpose of the wait(), notify(), and notifyAll() methods

Question :What is the purpose of the wait(), notify(), and notifyAll() methods?
Answer :The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods.