Limit generic type in subinterface in Java

Question

Say I have this interface structure:

public interface ItemRequestConverter<IR extends ItemRequest> {
    Target convert(IR request);
}

public interface CreateItemRequestConverter<CIR extends CreateItemRequest>
    extends ItemRequestConverter<ItemRequest> {
}

public class CreatePartRequestConverter implements CreateItemRequestConverter<CreatePartRequest> {
    @Override
    public Target convert(CreatePartRequest request) {
        ...
    }
}

Now I wondering whether this is possible at all. I doubt that. When I create CreatePartRequestConverter the signature of the overridden method is the super type ItemRequest. This is not desired.

Can you explain what you're trying to achieve? I don't quite understand. — Someone
– Someone, Commented Jan 30, 2014 at 13:00

Olivier Croisier · Accepted Answer · 2014-01-30 13:10:15Z

1

I think your CreateItemRequestConverter class signature should be like this :

interface CreateItemRequestConverter<CIR extends CreateItemRequest>
        extends ItemRequestConverter<CIR> {

}

Test :

interface ItemRequestConverter<IR extends ItemRequest> {
    Target convert(IR request);
}

interface CreateItemRequestConverter<CIR extends CreateItemRequest>
        extends ItemRequestConverter<CIR> {

}

class CreatePartRequestConverter implements CreateItemRequestConverter<CreatePartRequest> {
    @Override
    public Target convert(CreatePartRequest request) {
        return null;
    }
}

class ItemRequest {
}

class CreateItemRequest extends ItemRequest {
}

class CreatePartRequest extends CreateItemRequest {
}

class Target {
}

answered Jan 30, 2014 at 13:10

Olivier Croisier

6,14927 silver badges34 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Michael-O Over a year ago

Stupid me, that is perfect! Merci Olivier!

Someone · Accepted Answer · 2014-01-30 13:05:18Z

0

So you want to make the overridden method accept a generic type that extends ItemRequest? You'll want to use a generic method, e.g:

<T extends ItemRequest> Target convert(T request);

answered Jan 30, 2014 at 13:05

Someone

5513 silver badges14 bronze badges

Collectives™ on Stack Overflow

Limit generic type in subinterface in Java

2 Answers 2

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related