A Simple Problem with join()...

[Prashanth Lingala]

Dear Friends, i have written a simple program...

 
class Join implements Runnable {

public void run() {
for(int i=0; i<5; i++) {
System.out.print(Thread.currentThread().getName() + " : " + i + "..<>");
}
System.out.println();
}
}
 
class JoinDemo {
public static void main(String[] args) {
 
Join justJoin = new Join();



try {
 
Thread t1 = new Thread(justJoin,"One  ");
Thread t2 = new Thread(justJoin,"Two  ");
Thread t3 = new Thread("Three");
t1.start();
t2.start();
t3.start();
t1.join();
t2.join();
 
for(int i=0; i<5; i++) {
System.out.print(t3.getName() + " : " + i + "..<>");
}
System.out.println();

}
catch(InterruptedException ie) {}
}
}
 

The output is...

One : 0..<>One : 1..<>One : 2..<>One : 3..<>One : 4..<>
Two : 0..<>Two : 1..<>Two : 2..<>Two : 3..<>Two : 4..<>
Three : 0..<>Three : 1..<>Three : 2..<>Three : 3..<>Three : 4..<>

Press any key to continue...




My problem is i dont understand who is joining whom,
i actually dont know how join() works,
i have read the book, but it still is not very clear to me...

Regards
Prashanth Lingala

[James Carman]

The join() method, when called on thread "t" for instance, makes the currently executing thread (main in your case) wait until thread "t" dies (the run() method returns).

[Lionel Badiou]

Hello Prashanth,

t.join() may be read as : "stop the execution at this point until t has finished". In your sample code, the JVM creates a thread (named "main thread") in which your application runs then main()creates and starts 3 other threads. The join() methods simply force the main thread to stop until t1 and t2 has died (at the end of the run() method).

Hope that helps,

[Prashanth Lingala]

Thanks James and Lionel
Thank you

Regards
Prashanth Lingala

[Ernest Friedman-Hill]

Moving to our "Threads and Synchronization" forum.