Question

With normal instance methods, local variables are thread safe.

If I have the following in a static method:

int i = 0;
i += 3;

Would this be thread-safe? Is there any catch?

Also, what exactly does it mean when each variable has its own stack? Does that mean its own stacktrace?

Thanks

Answer 1

If the lines you posted are inside the method, then there’s no reason why it shouldn’t be threadsafe. The threads aren’t interacting in any way – each thread sees a different i.

The catch comes if you try to share the value of i between threads, for example by making i a static field. Then it’s possible to get a race condition where you get different results depending on timing.

Regarding your second question, each thread has its own stack, not each variable.