quote:

---

Original post by Aldacron
More specifically, when you create a new thread in Java and flag it as a daemon by passing true to setDaemon, you are indicating to the VM that the thread should be terminated when thread which spawned it has terminated.

---

quote:

---

Original post by CaptainJester
That is not correct. There are 2 types of threads in Java. User threads and daemon threads. Daemon threads are basically threads that are there to provide a service to user threads. As an example, the garbage collecter is a daemon thread. The reason for the distinction is that the VM will only shut down when no user threads are alive.

---

quote:

---

Original post by Aldacron
Sorry, but it *is* correct. Yes, there are user threads and daemon threads. But when you create a new thread and call setDaemon(true), the new daemon becomes subordinate to the thread that created it . When the creating thread ends, the daemon dies with it.

So if you spawn any daemons off of the main thread, they will be killed when the app exits, since the main thread will be terminated.

---

public class Test
{
    public static void main(String [] args)
    {
        // bad style, used only to make the example shorter.

        
        Thread d = new Thread()
        {
            public void run()
            {
                int i = 0;
                while (true)
                {
                    System.out.println(i++);
                    try { Thread.sleep(500); }
                    catch (InterruptedException e) {}
                }
            }
        };
        
        d.setDaemon(true);
        d.start();
        
        Thread nd = new Thread()
        {
            public void run()
            {
                try { Thread.sleep(5000); }
                catch (InterruptedException e) {}
            }
            
        };
        
        nd.start();
        
        System.out.println("Main thread exiting");
    }
}

quote:

---

The reason for the distinction is that the VM will only shut down when no user threads are alive.

---

quote:

---

Original post by EkEk
So this Daemon Thread will be killed after user threads killed??
or is the VM will shutdown without give a damn about this Daemon Thread killed or still alive??

---

public class ThreadTest extends Thread {
	boolean daemon;
	boolean alive = true;
	int x = 0;

	public ThreadTest(boolean daemon) {
		this.daemon = daemon;
	}
	public void run() {
		while(alive) {
			if(daemon) {
				System.out.println("daemon thread running");
			}
			else {
				System.out.println("user thread running");
			}
			try {
				Thread.sleep(100);
				x++;
				if(!daemon && x >= 100) {
					alive = false;
				}
			}
			catch(Exception e) {
				e.printStackTrace();
			}
		}
		if(daemon) {
			System.out.println("daemon thread exiting");
		}
		else {
			System.out.println("user thread exiting");
		}
	}

	public static void main(String args[]) {
		System.out.println("Main user thread started");
		System.out.println("Starting daemon thread");
		ThreadTest td = new ThreadTest(true);
		td.setDaemon(true);
		td.start();
		System.out.println("Starting user thread");
		ThreadTest tu = new ThreadTest(false);
		tu.start();
		System.out.println("main user thread exiting");
	}
}