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

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 https://news.ycombinator.com/item?id=35133670