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📜 WAYPOINT LESSON

Checkpoint: ShoppingCart

⭐⭐ intermediate⏳ 30 min read📍 Lesson 116 of 256

A full class from a spec table — state, memory field, guarded undo.

Three fields (total, itemCount, lastPrice), a constructor, two mutators with a guard, two readers — the exact anatomy of an exam Class Design FRQ. The insight being graded: refundLast needs MEMORY (the last price), which is a state decision, not a syntax decision. When the spec table is silent about a case, the guard is your answer (empty cart → false, nothing changes).