Question

Given the following:

public class RegistryIdModel extends AbstractTableModel{
     ContactExtensionProviderLocal provider;
     .
     .
     .
    @Override
    public ContactRegistryIdProviderLocal getProvider() {
        // TODO Auto-generated method stub
        return provider;
    }
}

public abstract class AbstractTableModel extends AbstractModel{
    public abstract MutableEntityProvider getProvider();
}

public interface ContactRegistryIdProviderLocal extends MutableEntityProvider<EppContactRegistryId>  {
....some methods....
}

Is it a good/bad solution to let the
method in RegistryIdModel to Override
the return type to a
ContactRegistryProviderLocal?

If I do this, it makes my life easier but what might the effects be later on?

Tanks for any help or helpful comments!
Marthin

Answer 1

You cannot override the return type. You can only provide (or specify) narrow implementation. This is called covariant return types (since Java 5). For example

abstract class A {
    abstract Serializable getId();
}

abstract class B extends A {
    @Override
    abstract Number getId();
}

class C extends B {

    @Override
    Integer getId() {
        return 42;
    }

}