Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

mutator

A method whose job is to assign one field, such as setName.

A mutator (setter) assigns a field from an argument; it must apply the same validation as the constructor or it bypasses the class invariant.