Can an interface be a superclass?

Question

In the Java documentaion it states:

@Override annotation informs the compiler that the element is meant to override an element declared in a superclass.

I have a class that implements an interface and the implemented method statements have the @Override annotation.
Does this mean (according to the docs) that the interface is a superclass of my class? But how can it be, considering that interfaces only contain 'empty' methods, not methods that actually do stuff?

My code is LibGDX-related:

public class MouseAndKeyboard implements ApplicationListener {
    private Texture plane1;
    private Sprite mainPlane;
    private SpriteBatch mainSpritePacket;

    @Override
    public void create() {
        float w = Gdx.graphics.getWidth();
        float h = Gdx.graphics.getHeight();

        ...

Answer 1

For questions like this it's best to check the Javadoc. And the Javadoc mentions "supertype" not "superclass": https://docs.oracle.com/javase/8/docs/api/java/lang/Override.html

Answer 2

It's still called an interface, it prevents you from making mistakes, so you should use it however.

Checkout the JSR http://docs.oracle.com/javase/specs/#9.6.4.4

Chapter 9.6.4.4 @Override

also:

Should we @Override an interface's method implementation?

Answer 3

@Override always bothered me also, because it is used for both overriding the actual superclass method, and implementing an interface method. So, the documentation in taht part isn't written in the best way.

considering that interfaces only contain 'empty' methods

This isn't true anymore, in Java 8 interfaces can contain default implementations for declared methods.

Answer 4

The explaination in the documentation is a bit sloppy. An Interface is not a superclass because a class can only have one superclass but implement multiple Interfaces. But you should still use the @Override Annotation for interface methods to show that this method ins inherited (there is no different Annonation only for interface methods).