A thread problem

[sabah ammar]

hi pals,
i got this question
public class PrintJ extends Thread{
int j=0;
public void run(){
try{
Thread.sleep(5000);
}catch(Exception e){
}
j=100;
}
public static void main(String []a){
PrintJ t1=new PrintJ();
t1.start();
System.out.println(t1.j);
}}
Q.What you have to do to ensure that j will print 100?
A.you have to make t1 as Daemon Thread.
B.you have to join t1 to main.
C.value of j is set to 100;
D.you have to interupt the main method.

Please describe the answer to me which accordingly is option B.thank you very much.

[Joyce Lee]

Hi Sabah,

To make sure 100 (not 0) is printed, join() of t1 must be called before System.out.println statement.

  
public class PrintJ extends Thread{
    int j=0;    
    public void run(){
        try {
            Thread.sleep(5000);
        } catch(Exception e) { }
 
        j=100;
    }
    
    public static void main(String[] a){
        PrintJ t1=new PrintJ();
        t1.start();
 
        [B]try {
            t1.join();
        } catch (InterruptedException e) { } [/B]               
 
        System.out.println(t1.j);
    }
}

By calling t1.join(), it suspends the current thread, i.e. the main thread in this case, until t1 thread is completed.

Joyce
[ February 26, 2005: Message edited by: Joyce Lee ]

[sabah ammar]

exactly, main was suspended in other words....am very worried about threads for the exam...
anyways, thank you very much joyce .