volatile has nothing to do with thread safety or the memory model in modern C. It's strictly for access to memory-mapped resources, where common assumptions relied-on by optimizers may fail. It should never be used for multithreading, use proper atomics and other provided facilities instead.
True, the guarantee of atomicity does come up in Java wrt. fields of type long or double, for which atomicity is not provided by the Java memory model in the absence of volatile. More to the point, volatile in Java provides linearizability which is a bit stronger than simple atomicity.
While somebody writing concurrent Java code should definitely know the atomic classes, locks, and possibly var handles if they are implementing their own algorithms, they absolutely should also know the semantics of volatile. It does not provide thread safety in C or Java, but it’s very important in choosing how to define your data structures.
