Thread wait() and notify()

[Ayusarap Muhi]

Hello everyone,

I would just like to ask if the following code example in the Sierra Bates SCJP Reviewer below is correct. Is it possible for b.wait() in line 9 to wait forever if the notify() action in line 24 comes first?


1. class ThreadA {
2. public static void main(String [] args) {
3. ThreadB b = new ThreadB();
4. b.start();
5.
6. synchronized(b) {
7. try {
8. System.out.println("Waiting for b to complete...");
9. b.wait();
10. } catch (InterruptedException e) {}
11. System.out.println("Total is: " + b.total);
12. }
13. }
14. }
15.
16. class ThreadB extends Thread {
17. int total;
18.
19. public void run( ) {
20. synchronized(this) {
21. for(int i=0;i<100;i++) {
22. total += i;
23. }
24. notify( );
25. }
26. }
27. }


Thanks in advance.

[Ashok Kumar Babu]

Yes.

After line no:9, the main thread will wait(In Runnable state) until line no:24 executes or until the run method completes.

The Logic would be Main thread is waiting for threadB to complete the total and in Main thread you are displaying it.

[yu yong]

To Ayusarap:
I dont think so. In my mind, your code`s result is dynamic. Bug I am not sure about it. Can anyone explain it in detail. Thanks a lot.

[Sunny Jain]

try this in between line 4 and 6 of your code :

 
try{
   Thread.sleep(10000);
}catch(InterruptedException ie){
ie.printStackTrace();
}
   

Most probably(99.99999%) this will clarify Kathy and Bert..!!