JMEP is exactly what I’ve been beating my head over for the past few weeks. Seriously way better than what I was writing and, from the testing I’ve done, way more robust. If you’ve been looking for an open-source java parser for mathematical expressions, your search is over.
Never was interested in building a parser, I’m way more interested in building a cross-platform GUI fantasy baseball draft manager. Using JMEP cut my own codebase by several dozen classes and simplified the whole stats interface aspect significantly.