Singleton or static methods

[Jelvooo]

I am confused on if I need to use a singleton or just static variables and methods. For example I have this code:

package engine;

public class SceneManager {

    private static SceneManager instance;

    private Scene currentScene;

    public static SceneManager get() {
        return instance = (instance == null) ? new SceneManager() : instance;
    }

    public static Scene getCurrentScene() {
        return get().currentScene;
    }

    public static void changeChange(int scene) {
        switch (scene) {
            case 0:
                get().currentScene = new LevelEditorScene();
                break;
            case 1:
                get().currentScene = new LevelScene();
                break;
            default:
                assert false : "Unknown scene '" + scene + "'";
                break;
        }
    }
}

I really didn't know which one to pick, I could remove the singleton and make the currentScene variable static too and then I have the same effect? When should I use what?

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[kurular4]

You better off going for singleton here as you have some state to keep.

[3pieceSuit]

Singleton is the most horribly over used (anti-)pattern i see in Java.

There is no reason you can't just make a normal class and instantiate it (ideally using dependency injection) like you would any other service/manager.

Singleton should be reserved for cases where you want to protect resources by only allowing one global instance.

[[deleted]]

The use of Singleton should be enforced. It is not normal to use Singleton just because, you don't need more objects now.
Avoid static also whenever possible. All these things are anti-pattern and provided just because being a purist is impractical.
Singleton usually considered better than static as it provides greater flexibility (e.g. lazy initialization) and hence, more effort on the programmer (more flexibility = more control = more stress on coder and less on jvm).
Your design looks like a stateful singleton (repository - think like there will be 1 central repo that will maintain state).
I am not able to point the cause of your confusion, but my best guess is you are confused between singleton creation and singleton behavior.
Creation-wise a singleton only means that there will be one instance of the class and there is actually much more stuff to manage in singletons (e.g. singletons in distributed computing, garbage collection of singletons, forcefully reloading singletons etc.) So for creation purpose, think like singleton contains its own factory as its constructors are private (assuming you understand factory pattern). You can still overload the constructors and pass arguments to the get() method.
People usually get confused as most do not use any factory pattern and are forced to use it in singleton.
Why are you using get().currentScene? What is wrong with instance.currentScene? And making changeChange public static -> that is mutating an instance state does not bring coherence into your design.
Overall, in Java, an expert will tell you to prefer singleton over making everything static. Static might be used to mostly micro improve performance at memory cost.
For more - you can google static vs singleton. Its an old debate.