what's a good persistent collections framework for use in java?

Question

By persistent collections I mean collections like those in clojure.

For example, I have a list with the elements (a,b,c). With a normal list, if I add d, my original

Answer 1

Functional Java implements a persistent List, lazy List, Set, Map, and Tree. There may be others, but I'm just going by the information on the front page of the site.

I am also interested to know what the best persistent data structure library for Java is. My attention was directed to Functional Java because it is mentioned in the book, Functional Programming for Java Developers.