thread post answer

[Deepak Jain]

There was a post and after i submitted the answer it got deleted. Since i have put in the effort am still posting it

package demo.file;
 
public class TwoThreads {
 
static Thread laurel, hardy;
 
public static void main(String[] args) {
 
laurel = new Thread() {
public void run() {
System.out.println("A");
try {
hardy.sleep(1000);
} catch (Exception e) {
System.out.println("B");
}
 
System.out.println("C");
 
}
};
 
hardy = new Thread() {
public void run() {
System.out.println("D");
synchronized (laurel) {
try {
laurel.wait(10000);
} catch (Exception e) {
System.out.println("E");
}
}
System.out.println("F");
}
};
 
laurel.start();
hardy.start();
}
}

1) hardy.sleep(1000); -> is same as Thread.sleep(1000): This will simply cause the currently executing thread to sleep for 1 second. This shows static methods must always be invoked using class name to avoid confusion.

2)
Once both the threads are started, who gets to go first is upto scheduler hence "A" and "D" can get displayed in any order.
So the result could include
A
D

or

D
A

3)"B" will never get displayed in this code since no one is interrupting laurel thread.
a) In case hardy thread had a reference to laurel thread
b) laurel goes to sleep.
c) Before laurel wakes up , hardy interrupts laurel by invoking
laurel.interrupt() then "B" would have displayed.

4) laurel.wait(10000); This causes the laurel thread to
a) Wait on "laurel" object: Unless some one notifies on laurel object by invoking laurel.notify() [ This again might not cause the above thread to wake up , if there are more than one threads waiting on laurel"] or notifyAll().
OR
b) Wait for 10seconds and wakes up.

Since in this code noone is notifying , the only possiblity for laurel thread to comeout is after waiting for 10 seconds.

Further since again no one is interrupting laurel thread during its waiting period "E" would never be displayed.

5) Now these leaves us with C and F.
Once laurel & hardy threads come out of sleeping and waiting respectively they have one statement each System.out.println("C"); and System.out.println("F"); respectively to execute, before calling it a day.

The order in which these statements are executed is again depends on Thread schedular.
hence the result can include either

C
F

or

F
C


Hence the final result could be
D A C F
OR
A D C F
OR
A D C F
OR
D A F C

Hope this clears your doubt.

[Aum Tao]

Deepak, nice to see that you have provided the solution. But, it would be great if others can have a look at the original problem too.

[Henry Wong]

There was a post and after i submitted the answer it got deleted. Since i have put in the effort am still posting it

I don't know why, but certain people delete their questions (and topic), as soon as they get an answer. This obviously, isn't very nice to other users who may have similar questions -- but... oh well.

Henry

[Abhi vijay]

Sorry, Henry and Deepak. I deleted the question, because after running the program several times, I understood its working and thought it was worth deleting as it was a small problem( a trivial one).But I was unaware that Deepak had already posted an answer, when i was deleting.Sorry guys.
Thanks Deepak, for the effort.