How to get the state of a thread?

Question

this is how I define my thread

public class Countdown implements Runnable{

    public Countdown(){
        new Thread(this).start();
    }

    //...
}

Is it still possible to get the state of a thread if it is started that way? Like

 Countdown cd = new Countdown();
 cd.getState();

Answer 1

Is it still possible to get the state of a thread if it is started that way?

No. It is not.

If you want to be able to get the state, you have to keep a reference to the Thread; e.g.

public class Countdown implements Runnable{
    private final Thread t;

    public Countdown(){
        t = new Thread(this);
        t.start();
    }

    public Thread.State getState() {
        return t.getState();
    }
    // ...
}

---

By the way, there are other reasons why this is not a great pattern:

• If the reference to the Countdown object is lost (e.g. because of an exception during construction of the parent object), you will leak a Thread.

• Threads and thread creation consume a lot of resources. If there are a lot of these Countdown objects, or if they have a short lifetime, then you'd be better of using a thread pool.