JAVA threads (different stacks) synchronization

Question

I have a question regarding synchronization of code that is executed by several threads:

As far as I know each thread has its own stack, hence, non-static variables

Answer 1

Some key points which can help clarifying your doubts -

1. Objects are always allocated on heap.

2. Class level variables are shared across threads (thread of same object )

3. Local variables are always thread safe (if not exposed to outside world in non thread safe manner)