Can I place all this functionality into an enum?

user_13699210 0
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Can I squeeze this functionality into the enum? I would also like to use the enum in a switch statement in another file. I would also like to make things private if possible. I know you can do a lot more to enums in java but the literature is a little confusing.

public static class SCENE {
    public enum scene {
        MENU,
        PLAY
    }

    public static scene current = scene.MENU;

    public static void switchToMenu() {
        current = scene.MENU;
    }

    public static void switchToPlay() {
        current = scene.PLAY;
    }

};
enums java
2 Answers

Enum Classes (enum) are like a normal Classes, but restricted:

  • the only instances are the declared constants; no new instance can be created at run time, not even using reflection or clone;
  • direct superclass is Enum<E>;
  • cannot be extended;
  • cannot be declared abstract
  • some restrictions involving modifiers.

Despite of that (and some points I forgot), everything that can be done with a normal class, can be done with an enum: use all kind of fields and methods. Even each Enum Constant can have its own fields or methods.

BUT, as already commented, not everything is meaningful or recommended - like having a state, non-final fields.

public class Scene {

    public enum Type {   // maybe SceneType?
        MENU,
        PLAY;

        private void switchTo() {  // instance method, just an example
            current = this;  // bad example, should not change `Scene`'s state
        }
    }

    public static Type current = Type.MENU;

    public static void switchTo(Type type) {
        Objects.requireNonNull(type);
        current = type;
        /* alternative, to show switch usage
        switch (type) {
            case PLAY: 
                current = Type.PLAY; 
                break;
            case MENU:
                ...
        */
    }

    // just for demonstration, not the best solution
    public static void switchToMenu() {
        Type.MENU.switchTo();
    }

    public static void switchToPlay() {
        Type.PLAY.switchTo();
    }

}

not tested, no IDE was harmed (used), minor errors left for the user to solve

I do recommend, for above simple case, to only use the switchTo(Type) method in Scene; not the switchTo() in Type - added just as an example of what can be done. The Type.switchTo() method is strange, it is accessing a field of Scene, that is being more than just a type, wrong place for such functionality.

Obs: since Enum Classes work like normal classes, they can also be declared in an own file. But for the posted code, since bound to Scene, it can stay as a nested enum - must be accessed like Scene.Type.PLAY from other classes. (Your SCENE looks like being nested itself - static keyword not allowed on top level class - so the real path would be even longer, likeSomeClass.Scene.Type.PLAY)

Links:

Admin1

you can do like this using current as string

public enum Scene {
    MENU  ("MENU"),
    PLAY  ("PLAY");
    private final String current;
    private Scene (String current) {
        this.current = current;
    }
}
user_48564130
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