K and B Chapter 9

[kiruthigha rajan]

class Dudes {
4. static long flag = 0;
5. // insert code here
6. if(flag == 0) flag = id;
7. for(int x = 1; x < 3; x++) {
8. if(flag == id) System.out.print("yo ");
9. else System.out.print("dude ");
10. }
11. }
12. }
13. public class DudesChat implements Runnable {
14. static Dudes d;
15. public static void main(String[] args) {
16. new DudesChat().go();
17. }
18. void go() {
19. d = new Dudes();
20. new Thread(new DudesChat()).start();
21. new Thread(new DudesChat()).start();
22. }
23. public void run() {
24. d.chat(Thread.currentThread().getId());
25. }
26. }

And given these two fragments:
I. synchronized void chat(long id) {
II. void chat(long id) {
When fragment I or fragment II is inserted at line 5, which are true? (Choose all that apply.)
A. An exception is thrown at runtime
B. With fragment I, compilation fails
C. With fragment II, compilation fails
D. With fragment I, the output could be yo dude dude yo
E. With fragment I, the output could be dude dude yo yo
F. With fragment II, the output could be yo dude dude yo

The answer for this is F
could any one explain me the the process how F is obtained
im unable to understand the process
thanks in advance

[Piyush Joshi]

with synchronized chat method only one thread will be able to invoke this method (on static Dudes object d) at a time. Second thread will get a chance to invoke chat only when first chat call returns.
First chat call sets the static flag equal to thread id and then prints "yo" two times. then second thread invokes chat and prints "dudes" two times, and given the above logic second method call can not be made unless first finishes so output will always be "yo yo dude dude"