and you would use it ... how?

I've showed you an alternative encoding, maybe get to work and learn something yourself?

It's not exactly Java, but:

    Cons(1, Cons(2, Cons(3, Nil)))

Actually, Java does have sum types nowadays, and you can write a recursive list implementation like “new Cons(2, new Cons(3, Nil.nil()))”.

Here is a definition for a Maybe type, converting it to a List is left as an exercise to the reader :) : https://news.ycombinator.com/item?id=35133670

I just meant because I was eliding the `new`s.