I have started implementing a concurrency framework using Yielder to
provide Coroutines for Java. It is based on the Axon framework for
Python which is part of Kamaelia:
http://kamaelia.sourceforge.net/MiniAxon/
I have blogged about what I have done here:
http://blog.buni.org/blog/mbarker/Meldware/2007/08/24/Mini-Axon-for-Java
Mike.