I'm currently writing an MVC application and I need a class that can:
A: get, add and remove data(specifically a TreeSet of sorted strings that I want stored in memory, but I doubt the data itself is relevant.)
B: The data must be accessible to multiple controllers.
C: There can "presumably" only be one instance of this class. These controllers will often share this set.
D: Since the class will be accessed by multiple controllers, the class must be thread-safe.
It seems like an enum singleton would work for this problem but I've read that singletons are an anti-pattern and I'm curious as to possible alternatives?
I was thinking of maybe abstracting over this by creating one or multiple "API" classes that can modify the state of a single non-global instance(protected singleton?) containing our data and then passing these API classes into their respective controllers via dependency injection, but I feel like this may be kicking the can down the road? I genuinely don't know.