Java implements a very efficient way to interprocess communication among threads which reduces the CPU?s idle time i.e. A process where, a thread is paused while running in its critical region and another thread is allowed to enter (or lock) in the same critical section to be executed. This technique is known as Interthread communication which is implemented by some methods. These methods are defined in "java.lang" package and can only be called within synchronized code shown as:
|wait( )||It indicates the calling thread to give up the monitor and go to sleep until some other thread enters the same monitor and calls method notify() or notifyAll().|
|notify( )||It wakes up the first thread that called wait() on the same object.|
|notifyAll( )|| Wakes up (Unloack) all the
threads that called wait( ) on the same object. The highest
priority thread will run first.
All these methods must be called within a try-catch block.
Lets see an example implementing these methods :
Output of the Program:
In this program, two threads "Producer" and "Consumer"
methods of the class "Shared". At time of program execution,
the "put( )" method is invoked through the "Producer"
class which increments the variable "num" by 1. After
producing 1 by the producer, the method "get( )" is invoked by
through the "Consumer" class which retrieves the produced
number and returns it to the output. Thus the Consumer can't retrieve the number
without producing of it.
Another program demonstrates the uses of wait() & notify() methods:
Output of the program is:
Demo1 value is20
value is :40
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