Screenshot of the GUI: https://ibb.co/drnNqdG
Great for persons wanting to learn JavaFX. Made with the logic of simple string building and using the package called EvalEx to evaluate the string expressions, similar to eval with python.
Link to use EvalEx: https://github.com/uklimaschewski/EvalEx/blob/master/FAQ.md
Kudos to the creators of EvalEx.