How to delete Thread object from an array?

Question

The program I am creating requires an array of thread objects. More specifically I have a class which extends Thread. I am doing this so that each new object created runs on its own thread. If I want to kill the thread and remove it from the array element, so that I can create a new Thread object in that space, how do I do this? This is my thought.

I understand that removing reference to the thread will not actually stop the thread. To do this I would first need to interrupt the thread. To remove the thread object from the array, can I simply make it null? I.e.:

array[i].interrupt();    
array[i] = null;

And then I would be able to create a new thread in that space?

array[i] = new Thread();

Assume that the run method of the Thread objects handles interruptions properly etc.

What's stopping you from trying? Interrupting is not the same as stopping though. — f1sh, Feb 13 '17 at 13:24
This should work, but to ensure the thread is stopped before you create a new one, you can do array[i].join() before setting the element to null. — Maurice Perry, Feb 13 '17 at 13:25
Can you share your requirements, why do you need an array of thread objects ? — marknorkin, Feb 13 '17 at 13:29
@MauricePerry The OP would be calling `interrupt` on the `Thread` . — Chetan Kinger, Feb 13 '17 at 14:21
@MauricePerry What's the point of calling `join` on a thread that has been interrupted? — Chetan Kinger, Feb 13 '17 at 14:39
@CKing to make sure it's terminated. A thread can catch the InterruptedException — Maurice Perry, Feb 13 '17 at 14:42
@MauricePerry Do read [this](http://stackoverflow.com/questions/10632451/does-calling-thread-interrupt-before-a-thread-join-cause-the-join-to-throw) — Chetan Kinger, Feb 13 '17 at 15:01
There is no reason to assign `null` to an array slot if the next thing you do is assign a new Thread reference to the same slot. — Solomon Slow, Feb 13 '17 at 15:50

score 0 · Answer 1 · answered Feb 13 '17 at 14:18

To remove the thread object from the array, can I simply make it null

Yes. This should make the reference held at index position i to point to null. However, if you are setting the element at index position i to null and then immediately saying array[i] = new Thread();, you can skip the step where you set it to null and only use array[i] = new Thread(); instead.

Also note that just adding the element to the array won't start the newly inserted Thread. You would still need to call array[i].start() after inserting the new Thread in the array to start the new Thread.

That said, extending from Thread makes sense only if you plan to override some of the functionalities from the Thread class. (I personally don't see any valid use case for this). You should instead implement Runnable and pass it to the Thread constructor.

How to delete Thread object from an array?

1 Answers1