AbstractList etc. functionality as interfaces with default methods?

Attila Szegedi attila.szegedi at oracle.com
Fri May 8 09:41:56 UTC 2015

So I’m in a position where I’d need to have a class implement List, but it already extends something else, so I can’t have it extend AbstractList, which leaves me with a lot of boilerplate methods to implement.

Would it seem like a good idea to reimagine AbstractList and friends as interfaces with default methods? 

Of course, I know that technically for backwards compatibility we can’t really do this, but what we could do is:

public interface DefaultList<T> extends List<T> {
    … add all methods from AbstractList here as default methods …

public abstract class AbstractList<T> implements DefaultList<T> {

(I’ll hand-wave the issue of “protected int modCount” issue for now.)

Actually, this seems like such an obvious idea that I’m 100% sure it must’ve been considered before, but I can’t find any related discussion.


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