Reference assignment is atomic so why use AtomicReference

Question

I have simple general question about AtomicReference.

Why use AtomicReference if reference assignment is atomic in java?

Also I would like to ask if referen

Answer 1

Why use AtomicReference if reference assignment is atomic in java?

You need it when the decision on which the creation of the new value is based can depend on the previous value of the reference. For instance when implementing some LinkedList like data structure you wan't to set the head to a new node which refers to the previous node. In the time between reading the previous node and setting head to the new one some other thread could have concurrently updated the head reference's value. If our thread would not be aware of this change, it would go lost.

Do we need volatile to have reference assigment atomic?

The operation itself would be performed atomic on the CPU core executing it but there are no guarantees that threads on other cores will be aware of it on the next read.