threads

[hema janani]

Question 1.
Given the code
1public class ThreadDemo extends Thread{
2 public void run(){
3System.out.println("Thread Started");
4//What Code ???
5 System.out.println("Done");
6 }
7 public static void main(String[] arg){
8ThreadDemo td = new ThreadDemo();
9td.start();
10 }
11}
Which of the following given code segment(s) below can be placed at line 4 to print both "Thread Started" and "Done" to the standard output.

A.suspend(); resume();
B.sleep(10000);
C.yield();
D.yield(); resume();
E.All the above
ans given is c & d why not a.

[chetan nain]

gosh,
c and d sure seem unlikely. in my opinion, the correct answers should be a,b,c.
a: suspend() and resume() should speak for themselves
b: after a period of 10000ms., thread goes to ready state. the scheduler, having determined that no other threads are in pool, reschedules the same thread for exec
c: same reason as above
d: incorrect, as resume() can only be used upon a thread that has been suspend()ed
am i correct or just confused??

[Ramesh Donnipadu]

No Chetan! You can't use sleep() method as it throws interrupted exception, it has to be enclosed in a try-catch construct.
(a) suspend() followed by resume() does not resume execution of thread by itself. So "Done" is not printed. When a thread invokes suspend() method its execution is suspended and the thread keeps waiting. I am not sure if it can resume execution on its own. I suspect it has to be another thread that has to invoke resume() on this thread.
yield() method immediately gives away its execution privilege and enters ready state. So it is immaterial whether resume() is called after invocation of yield or not.
So, correct answers are C and D.
[This message has been edited by Ramesh Donnipadu (edited September 23, 2000).]

[Surya B]

Hi
You cannot use sleep(10000) because
Exception java.lang.InterruptedException must be caught, or it must be declared in the throws clause of this method.
yield();--is ok
yield();resume();--is ok
Regading the first option suspend and resume in this case the only user Thread in the entire application is suspended indefinately and the suspended thread cannot unsuspend themselves,look at this discussion for further clarification
http://www.javaranch.com/ubb/Forum24/HTML/003783.html
Surya

[chetan nain]

oops, let me correct myself.
option d is actually correct, as it is permitted to resume() a thread
that has never been suspend()ed. the thread just goes about its normal
business
option b is a tricky one. it would have been correct if the sleep(10000)
would have been enclosed in a try{} catch{InterruptedException e} block
so the correct answers are c,d
however, theres another issue here. for options a and d, compiler
complains about method deprecation and suggests alternative method use.
so, speaking deeply, the only option that will compile cleanly and
print the required is c.
sherrifs, please help

[paul wheaton]

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