Question

What (if anything) is wrong with the following interface?

public interface WorldsBestInterface {
    void favoriteMethod(int greatValue){
        System.out.println("Thanks for the smile");
    }
}

I’m having an issue figuring this out.

Answer 1

Shouldn’t contain implementation. Interface contains just method declaration, it doesn’t contain implementation.

void favoriteMethod(int greatValue){
        System.out.println("Thanks for the smile");
    }

It should be

 public interface WorldsBestInterface {
    void favoriteMethod(int greatValue);
}