Starting new thread while old thread is running

Question

What will happen if I assign a new thread object to a thread variable and run it while the thread object that was bound to the variable before is still running? Will it be garbage collected and destroyed? Or will they run in parallel?

Something like this:

class ThreadExample implements Runnable {
    public void run() {
        // Something that runs for a long time
    }
}

public class ThreadExampleMain {
    public static void main(String[] args) {
        // Client Code
        ThreadExample e = new ThreadExample();
        Thread t = new Thread(e);
        t.start();

        e = new ThreadExample();
        t = new Thread(e);
        t.start();
    }
}

Will this start two threads running parallelly or will the first thread stop and be garbage collected?

What thread library are you using? Can you show us some example code to demonstrate what you're proposing? — Dai, Apr 18 '14 at 03:55

score 0 · Accepted Answer · answered Apr 18 '14 at 04:05

If you a talking about Java then answer is: they will run in parallel. Garbage collection has nothing to do with the thread management.

You can see it with this sample code:

public class LostThread {
    public static void main(String[] args) {
        for (int i = 0; i < 10; i++) {
            final int value = i;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    while (true) {
                        try {
                            System.out.println(value);
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }
                }
            }).start();
        }
    }
}

Main finishes after ten threads are created, but they are still running.

How do I check if a thread is running and stop it before starting a new thread? — streetsoldier, Apr 18 '14 at 04:09
See this topic on SE, it explains how to stop threads: http://stackoverflow.com/questions/19894607/java-how-to-stop-thread — Denis Kulagin, Apr 18 '14 at 04:11

Starting new thread while old thread is running

1 Answers1