Question

I implement a Singleton using the enum approach:

public enum Singleton {
    INSTANCE;

    public void doStuff(String stuff) {
        System.out.println("Doing " + stuff);
    }
}

How do I call it right (I don’t mean execute, just how to write it)? Is it still a class or now an enumeration? I’m just interested in the theoretical part.
If talking about object orientation and classes, can I say I created a Singleton class of type enumeration?

Answer 1

An enum in Java is just a class (as you seem to know), so you should be fine calling it any of the above. It’s a bit subjective, but I think it depends on which aspects of it you want to highlight.

• if you want to highlight that it’s this thing that can instantiate an object with state and methods, call it a class
• if you want to highlight the object itself, call it the singleton instance
• if you want to highlight that it’s using the enum to implement the singleton pattern, call it an enum
• if you want to highlight the fact that it’s a singleton (without referring to how that pattern is implemented), call it a singleton
• if you want to highlight the fact that it’s a singleton pattern implemented via an enum, call it a singleton enum

I would understand any of those terms, and I wouldn’t judge someone for using one vs another.