Java: How to atomically replace all values in a Map?

Question

I have a stateful bean in an multi-threaded enviroment, which keeps its state in a map. Now I need a way to replace all values of that map in one atomic action.

Answer 1

As client code maintains a reference to the bean not the map, replacing the value (i.e. the whole map) would seem to be the simplest solution.

Unless there's any significant performance concerns (although using locking is likely to perform worse and less predictably unless the map is huge) I'd try that before anything requiring more advanced knowledge.

It's how a functional programmer would do it.