The article doesn't even cover gen-class?

You can use Clojure to create a Java library. Then the Java (or Scala or JRuby or Jython) code that calls it doesn't even need to know it is calling Clojure rather than an ordinary Java class.

The only problem I have with this so far is that it doesn't seem to support generics, so I end up creating the kind of APIs that you would expect from Java 4. Would LOVE for someone to show me I'm wrong about that.

http://richhickey.github.com/clojure/clojure.core-api.html#c...

Anyway, the article looks like the kind of stuff that was being written over a year ago, before gen-class existed, but with considerably less depth.