Your job: clean up the code as much as you can.
This is "real" code, i.e. actually used in a production piece of working open source software. It is what it is; please do not judge (it is not mine, either). Note that it's a little worse than it appeared in production--I simply inlined a few methods to add a little fun to the exercise.
There are tests, I believe they are sufficient, but I could be wrong. (Maybe a code coverage run would tell more.)
The tests are a little lame. Feel free to clean up and add more.
This is a Gradle project. I was able to successfully load it into IntelliJ IDEA using its defaults. Eclipse, who knows, it won't even start on me at this point, but it should similarly work using the Gradle Buildship plugin.
Worst case, it's only a few source files, and you could consider creating the project from scratch if you have any issues.