The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource.

When you call the wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods.

* wait( ) tells the calling thread to give up the monitor and go to sleep until some other
  thread enters the same monitor and calls notify( ).
* notify( ) wakes up the first thread that called wait( ) on the same object.
* notifyAll( ) wakes up all the threads that called wait( ) on the same object. The 
  highest priority thread will run first.