Why to use AtomicRefernce when reading & setting simple reference is already atomic operation

Question

Could somebody please clarify my doubt on AtomicReferences. As par java memory model reading & writing references is always an atomic operation irrespective of 32 bit or 64 bit machine. So in what scenario using AtomicRefernce will be useful.

Answer 1

There are other operations provided by AtomicReference that you can't implement with normal references.

For instance to make sure which value your are replacing:

ref.compareAndSet(expectedCurrentValue, newValue);

To get the last value and replace with something else:

oldValue = ref.getAndSet(newValue);

With AtomicReference you can do those operations safely even when multiple threads are trying to access the same references.