regarding deadlock

[velan vel]

1. public class SyncTest{
2. public static void main(String[] args) {
3. final StringBuffer s1= new StringBuffer();
4. final StringBuffer s2= new StringBuffer();
5. new Thread () {
6. public void run() {
7. synchronized(s1) {
8. s2.append("A");
9. synchronized(s2) {
10. s2.append("B");
11. System.out.print(s1);
12. System.out.print(s2);
13. }
14. }
15. }
16. }.start();
17. new Thread() {
18. public void run() {
19. synchronized(s2) {
20. s2.append("C");
21. synchronized(s1) {
22. s1.append("D");
23. System.out.print(s2);
24. System.out.print(s1);
25. }
26. }
27. }
28. }.start();
29. }
30. }
}
Which two statements are true? (Choose Two)
A. The program prints "ABBCAD"
B. The program prints "CDDACB"
C. The program prints "ADCBADBC"
D. The output is a non-deterministic point because of a possible deadlock condition.
E. The output is dependent on the threading model of the system the program is
running on.
Answer: D, B

------------------------------------------------------------------
$ Velan Vel @ SCJP 1.4 $
You learn From Your Failures, Others Will Learn From Your Success
------------------------------------------------------------------

[Mani vannan]

hi velan,
I think that options D & E are correct.If this program runs in a round robin fashion, surely dead lock will occur(Option D). However, it all depends on the thread implementation of a system. (Option E)

[velan vel]

} i think mani we are synchronized

[Seb Mathe]

If the first thread executes before the second one, ABABCD will be printed.
If the second thread executes before the first one, CDDCAB will be printed.
But a deadlock may occur :

1. Thread1 requires lock on s1 (synchronized(s1)) -> OK
2. Thread2 requires lock on s2 (synchronized(s2)) -> OK
3. Thread1 requires lock on s2 -> WAITING
4. Thread2 requires lock on s1 -> WAITING
DEADLOCK