His other project "Byte Me", along with judicious javap usage, has been super useful for me learning JVM bytecode so I could make a machine learning model compiler for the JVM (basically compile your ML models as native code; ONNX, tree ensembles, regressors, classifiers, etc as native JVM classes with no massive runtime needed)

still in the works, but its here for those interested: Petrify: https://github.com/exabrial/petrify