I'll be the first to agree that Java-style class hierarchies and duck typing don't mix well, but not every dynamic language is Python. Clojure, for example, is

I'll be the first to agree that Java-style class hierarchies and duck typing don't mix well, but not every dynamic language is Python. Clojure, for example, is very easy to refactor when it's (very rarely) necessary. Not saying static typing doesn't have it's advantages – tooling is probably Java's greatest strength – but there are other, equally valid, solutions to the problem.