Stopping a thread

[userj2ee]

Hi,

Can anyone tell me what are the different ways to stop a thread?

Thanks

[JosAH]

Hi,

Can anyone tell me what are the different ways to stop a thread?

Thanks

The only safe way is to programmatically ask it to stop; of course the thread has to cooperate, i.e. there is no safe way to slice its throat and kill it. Your runnable method has to test, say, a boolean variable repeatedly and when it has been set to true (by another thread) it has to quit.

kind regards,

Jos

[userj2ee]

thanks for your reply Jos.

As u suggested that we should use the approach of having a boolean variable to stop a thread. The same approach is discussed at multiple places where use of volatile variable is recommended so that all threads should refer to the same copy. I understood this concept. But have one confusion .. Why volatile has to be used? Cant we achieve the same by using a static variable instead of volatile?

Thanks

[JosAH]

thanks for your reply Jos.

As u suggested that we should use the approach of having a boolean variable to stop a thread. The same approach is discussed at multiple places where use of volatile variable is recommended so that all threads should refer to the same copy. I understood this concept. But have one confusion .. Why volatile has to be used? Cant we achieve the same by using a static variable instead of volatile?

Thanks

If you want to stop everything at once a static condition variable would do; and yes, always make those variables volatile because a compiler might, and pay special attention to the verb 'might', optimize out the test for non volatile variables; basically your Runnable should look like this:

public void run() {
   while (!stop) {
      process(); // do real work here ...
   }
}

somewhere else in that class you have a (static) volatile boolean stop variable that can be set to true by another thread.

kind regards,

Jos