Question

I have seen different questions regarding this, but I still find this topic to be very confusing.

All I want to do, is have an abstract class that implements an interface, and have a class extending this abstract class so that the hard class needs to implement getKommune() and setKommune(Kommune kommune), but not the other method, because that is in the abstract class.

I have the following interface.

public interface KommuneFilter {

    <E extends AbstractKommune<?>> void addKommuneFromCurrentUser(E e);

    Kommune getKommune();

    void setKommune(Kommune kommune);
}

And this Abstract class

public abstract class AbstractKommune<E extends AbstractKommune<?>> implements KommuneFilter {
    @PrePersist
    void addKommuneFromCurrentUser(E e) {
            Kommune k = e.getKommune();
    }
}

And I want to use it like this

    public class Person extends AbstractKommune<Person> {
        private Kommune kommune;             
        public void setKommune(Kommune kommune) {this.kommune=kommune;}
        public Kommune getKommune() {return kommune;}
    }

However, I get

Name clash: The method of has the same erasure of type but does not override it

Why isn’t it correctly overridden?

UPDATE

Thanks to @Bozho, the solution is this:

public interface KommuneFilter<E extends AbstractKommune<?>> {
    public void addKommuneFromCurrentUser(E e);
}

public abstract class AbstractKommune<E extends AbstractKommune<?>> implements KommuneFilter<E> 

public class Person extends AbstractKommune<Person>

Answer 1

I’d suggest making the interface generic, rather than only its method:

interface KommuneFilter<E extends AbstractKommune<?>> { .. }

And then

public abstract class AbstractKommune<E extends AbstractKommune<?>> 
     implements KommuneFilter<E>