For compsci, we were supposed to make a fractional calculator. Naturally, I looked for a way to cheese the assignment. See Nashorn.java.
But since that kinda defeated the point of the assignment, I did end up having to do it for real. See FracCalc.java. I still wasn't satisfied with my Java version. With Joshua's help, I was able to read and understand the architecture of a popular open source JavaScript parser named acorn. Joshua also helped me debug a lot of this when it was broken and showed me how to make a basic Makefile. This is the first time I ever used make. It's been invaluable to me since then. Click for curse.
This fractional calculator can handle order of operations for the operators
+, -, *, /, and _. It also understands parens.