http://tutorials.jenkov.com/java-concurrency/thread-safety.html

• Local Variables

• Local Object References

• Object Member Variables

• The Thread Control Escape Rule

The Thread Control Escape Rule

When trying to determine if your code's access of a certain resource is thread safe you can use the thread control escape rule:

If a resource is created, used and disposed within
the control of the same thread,
and never escapes the control of this thread,
the use of that resource is thread safe.