how to design an interface for different object to using them in a builder design pattern? - oop

Question

I have at least two different classes like following :
//NOTE : these two classes have getter and setter also
class Artist {
String artistName;
String artistWebsite;
String artistDbpedia;
String artistImage;
List<String> astistAlbumsName;
List<String> astistAlbumsUrl;
}
class Venu {
String VenuName;
String VenuWebsite;
String VenuDbpdia;
String VenuImage;
String VenuDescription;
List<String> venuFans;
}
I want to have a producer class to get an xml file as an input and detect the type of xml (venu/artist) then start to create a product object based on the input.
the problem :
I want to create an interface for aggregate the similarity between above two classes so my interface would be:
interface Model {
public String getImage();
public String getName();
public String getWebsite();
public String getdbpedia();
}
Then I can implement this interface in my builder class and above two classes but how about those different methods?
such as getVenuFans / getArtistAlbumName / etc....?
How can I call them from my producer?
this is my builder :
Class Builder implements Model {
public String getImage(){}
public String getName(){}
public String getWebsite(){}
public String getdbpedia(){}
}
and this can be my producer :
Class Producer {
public Producer()
{
Builder b = null;
//assume Venu and Artist implements Model
b = (Builder) new Venu();
//I don't have access to getVenuFans()!
b = (Builder) new Artist();
//I don't have access to getArtistAlbumsName() / etc...
}
}

Answer 1

You don't have access to those methods because you're casting the objects to a Builder, and Builder doesn't have those methods.
I see what you're trying to do, but I don't think it will work. For example, getVenueFans (I'm assuming you mean venue) is only appropriate for the Venue class. It doesn't make sense to try and abstract that into an interface that other non-Venue classes will implement.
I think what you have is good: You've abstracted the common methods into an interface. To call the methods on Venue and Artist, the consuming code will need to cast the objects to the appropriate type, then call the methods on it. And that's not as bad as you might think. It's the consuming code that knows what type it's dealing with (otherwise, why would it be trying to call getVenueFans?), so that's the point where it makes sense to cast and call the method directly.