Message is a way of thread communication. By this process a Java thread can communicate with another. Java uses wait( ), notify( ), and notifyAll( ) methods in a synchronized environment for interthreaded and interprocess communication.
wait method: It is used to notify a thread to go to sleep.
final void wait( ) throws InterruptedException
notify method: It is used to wake up a thread.
final void notify( )
notifyAll method: It is used to wake all threads for execution. The thread which would be picked up for execution must be the highest priority thread.
final void notifyAll( )