The machine inventory

Cumulative review is problems-first: reread nothing, re-derive everything. The course's machine inventory, as a self-test checklist:

• [ ] accumulator / counter / flag / sentinel — can you write each in 15 seconds, correctly seeded?
• [ ] state table tracing — frames for calls, objects, recursion?
• [ ] String API edges — substring(a, b) length = b − a?
• [ ] array modes — when backward, when pairwise, when index?
• [ ] ArrayList mutation — remove backward, insert backward, size() shifts live?
• [ ] 2D orientation — r before c, g[r].length inner bound?
• [ ] dispatch — reference type vs object class; constructor chains?
• [ ] recursion edges — base answers with zero info; two-branch call counts?
• [ ] FRQ workflow — eight steps without the sheet?
• [ ] salvage — skeleton, adjacent part, no panic-erase?

Anything unchecked: return to that module's lab (not its lessons) — problems re-teach what prose only introduced. That is the ratio this course promised: the review is also problems.