wait(),notify() problem

[Sonali Sehgal]

can someone please explain these methods wait(),notify() and notifyall()

[Wouter Oet]

What is your question? Just read the documentation of the Object class.
There are many topics about these functions and many webpages explaining them.

[Sonali Sehgal]

can someone explain what does wait() and notify() are used in a java program.How do they coordinate with each other??

[Henry Wong]

Sonali Sehgal wrote:can someone explain what does wait() and notify() are used in a java program.How do they coordinate with each other??

The wait() and notify() methods implemention notifications between threads. In Threading speak, they implement the condition variable functionality.

So... How much threading do you know? Do you understand synchronization? And of course, condition variables? Anyway, the Sun tutorial on threading is a good place to start....

http://java.sun.com/docs/books/tutorial/essential/concurrency/

Henry

[Sonali Sehgal]

class ThreadB  extends Thread {
    int total;
    @Override
public synchronized void run() {
    
        for(int i=0;i<100;i++){
            total+=i;
            //System.out.println("Hello");
        }
        notify();
        System.out.println("Notification received");
    
}
}
class ThreadA {    
    public static void main(String[] args) {
       ThreadB b=new ThreadB();
       b.start();

       synchronized(b){
           try{
                   System.out.println("Waiting for b to complete....");
                   b.wait();
                   System.out.println("waiting done");

           } catch(InterruptedException e) {
           }
           System.out.println("Total is: " +b.total);
       }
    }

}

In the above program how can someone explain how does wait() and notify() coordinate with each other...This program executes successfuly and the output is
:-
Waiting for b to complete....
Notification received
waiting done
Total is: 4950

This is a kathy sierra question....My question is why does notifcation is received prior to waiting done...???....How does both work in relation with each other...

[Jesper de Jong]

Note: The correct way to use the "Code" button is to click it ONCE (do not double click it!) so that a [ code ] start tag is inserted in your text; then paste the code, then click the "Code" button again ONCE so that a [ /code ] end tag is added.

Do not double-click the "Code" button, because that will insert a start and end tag after each other, and so your source code will not be in between the tags.

[Sonali Sehgal]

Mr Young, I will take care to click only once.......................

[Massimo Battestini]

When notify() is reached, the thread waiting on that object will be notified (ThreadA in this case).

So ThreadA will be moved into the pool of live threads, but it won't be running until ThreadB has finished;

this is because ThreadB hasn't released the lock yet and ThreadA needs b's lock before moving to System.out.println("waiting done") which is contained in a block synchronized on b.

[Sonali Sehgal]

Thanks a lot Massimo...I understood this topic.................Thanks for clarification...