Question

I’m trying to get started with learning threading in Java and here’s a simple example that I tried from here
Here’s my code :
A simple main class:

    package com.vogella.Thread;

  import java.util.ArrayList;
 import java.util.List;

      public class Main {
public static void main(String[] args) {
    // We will store the threads so that we can check if they are done
    List<Thread> threads = new ArrayList<Thread>();
    // We will create 500 threads
    for (int i = 0; i < 500; i++) {
        Runnable task = new MyRunnable(10000000L + i);
        Thread worker = new Thread(task);
        // We can set the name of the thread
        worker.setName(String.valueOf(i));
        // Start the thread, never call method run() direct
        worker.start();
        // Remember the thread for later usage
        threads.add(worker);
    }
    int running = 0;

    do {
        running = 0;
        for (Thread thread : threads) {
            if (thread.isAlive()) {
                running++;
            }
        }
        System.out.println("We have " + running + " running threads. ");//-A
    } while (running > 0);

}
}

and the MyRunnable class is as follows :

package com.vogella.Thread;

public class MyRunnable implements Runnable {
private final long countUntil;

MyRunnable(long countUntil) {
    this.countUntil = countUntil;
}
@Override
public void run() {
    long sum = 0;
    for (long i = 1; i < countUntil; i++) {

        sum += i;
    }
    System.out.println(sum);
    System.out.println("Test123");
}

}
And this is my output

  49999995000000
   Test123
   50000005000000
  Test123
  50000015000001
   Test123...

However I dont understand why the line marked with comment A in Main.java never prints. Any insight on this would be helpful.
Thanks!

Answer 1

It should print. Check you’re not missing it in the program output.
Try commenting out the println()’s in your Runnable