In my program, I am creating several threads in the main() method. The last line in the main method is a call to System.out.println(), which I don't want to call until all the threads have died. I have tried calling Thread.join() on each thread however that blocks each thread so that they execute sequentially instead of in parallel.
Is there a way to block the main() thread until all other threads have finished executing? Here is the relevant part of my code:
public static void main(String[] args) {
//some other initialization code
//Make array of Thread objects
Thread[] racecars = new Thread[numberOfRaceCars];
//Fill array with RaceCar objects
for(int i=0; i<numberOfRaceCars; i++) {
racecars[i] = new RaceCar(laps, args[i]);
}
//Call start() on each Thread
for(int i=0; i<numberOfRaceCars; i++) {
racecars[i].start();
try {
racecars[i].join(); //This is where I tried to using join()
//It just blocks all other threads until the current
//thread finishes.
} catch(InterruptedException e) {
e.printStackTrace();
}
}
//This is the line I want to execute after all other Threads have finished
System.out.println("It's Over!");
}
Thanks for the help guys!
Eric
Best Answer
You start your threads and immediately wait for them to be finished (using
join()
). Instead, you should do thejoin()
outside of the for-loop in another for-loop, e.g.: