Another old project. This one is from 12-23-2010, originally intended for the 0.2 release of UQC Lib, which I now think will be more useful split up into smaller, discrete parts.
Enum State Machine is a simple state machine built in Java and using enums to define the various states. In addition to controlling the possible transitions, callbacks can be added between states or on entering and exiting a state.
Simple, clean, and provides a great, thread-safe way of controlling the flow of a process between various states. Check out the project page for more information.