ยป pip install jep
I'm aware of the Jython project, but it looks like this represents a way to use Java and its libraries from within Python, rather than the other way round - am I wrong about this?
Yes, you are wrong. You can either call a command line interpreter to run python code using Jyton or use python code from Java. In the past there was also a python-to-Java compiler, but it got discontinued with Jython 2.2
I would write a Python module to handle the text and language processing, and then build a small bridge in jython that your java program can interact with. The jython bridge will be a very simple one, that's really only responsible for forwarding calls to the python module, and return the answer from the python module to the java module. Jython is really easy to use, and setup shouldn't take you more than 15 minutes.
Best of luck!