Skip to content
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

final class

A class that can't be extended, or with final on a method, one that can't be overridden.

final on a class forbids subclasses (cannot inherit from final); final on a method forbids overriding (overridden method is final).

Read the full section →