Stage 5 · Lesson 1 of 10
Classes, objects and encapsulation
A class bundles data with the behaviour that changes it, and an is one instance of that class. The point is control, not syntax. Picture a BankAccount that keeps its balance .
It offers deposit and withdraw methods that refuse a negative amount, so no other code can put it into an invalid state. That idea is encapsulation. Use a class when data and the rules about it belong together. A plain is fine when there is no state (stored data) to protect.
Common trapmaking everything a class because a tutorial did, or exposing every field through a , which gives you the ceremony without the protection.
A question to check yourself, an AI practice session and 2 cheat sheet entries come when you add the roadmap to your account. Add it
Resources for this stage
Start with· follow one of these
- CoursePaidGrokking SOLID Design Principles
Design Gurus · Beginner · $50 one-time
Five principles with code examples, including when applying them makes code worse
- GuideFreeRefactoring.Guru: Code Smells and Refactoring
Refactoring.Guru · Beginner
Free catalogue of code smells and the small refactorings that fix each one