Typed persistent data structure a la Clojure, done in Java?

Question

In particular an immutable List with a cons operation would be welcome.

Answer 1

There are multiple solutions posted in Cons’ing a List in Java. And immutability can be added with:

List l;
...
l = Collections.unmodifiableList(l);

Answer 2

Dug around a little bit longer. This library probably comes closest: http://functionaljava.googlecode.com/svn/artifacts/2.22/javadoc/index.html . I would imagine that it would be possible to use Clojure's collection classes directly, but I'm not sure if would feel all that natural. (And I don't necessarily need to 'transactional' behaviour.)

Answer 3

I've written a bunch of persistent data structures in Java. My "PersistentList" is pretty close to what you want.

http://code.google.com/p/mikeralib/source/browse/trunk/Mikera/src/mikera/persistent/PersistentList.java