I just released Jambda on Github, a small project in which Johan Kullbom and Joakim Ohlrogge has taught me all I can absorb about functional programming. I have mostly contributed with documentation using my tool Bumblebee in order to learn the concepts. The code is mostly written by Johan.
Jambda is a small Java library with typesafe implementations of options, unions, curryable functions, and a bunch of sequence functionality, like map, fold and filter.
The result is also a rather interesting use of Java generics where we probably have pushed the generics implementation to the limit (I say “we” but mostly I mean Johan).
The documentation is available here. Check it out! Any feedback is welcome.