Is there any benefit in implementing a interface in a subclass even though the superclass implements the same interface

Question

When I was seeing the declaration of ArrayList

class ArrayList extends AbstractList
    implements List, RandomAccess         


        

Answer 1

Yes. It could've been omitted. But thus it is immediately visible that it is a List. Otherwise an extra click through the code / documentation would be required. I think that's the reason - clarity.

And to add what Joeri Hendrickx commented - it is for the purpose of showing that ArrayList implements List. AbstractList in the whole picture is just for convenience and to reduce code duplication between List implementations.

Reference: Why does ArrayList have "implements List"?