Volatile keyword on Atomic Variable

Question

The following code is valid in Java

volatile AtomicInteger a = new AtomicInteger(123);

Do we require volatile keyword on Atomic variables such as AtomicInteger ? Or is volatile superfluous?

Answer 1

It's superfluous for most sane use cases, but conceivably applicable to some weird cases -- not that I can think of any. When in doubt, use final .

Answer 2

volatile is superfluous because the variable inside the AtomicInteger already is volatile and will provide the happens-before relation that is required. Just make the field final.