Stage 1 · Lesson 1 of 8
Classes, objects and responsibilities
A class is a blueprint that keeps some data () together with the code allowed to change it (methods). An object is one instance made from that blueprint, with its own values. The point is not the syntax.
It is that each rule has one home: to learn how an order can be cancelled, you read the Order class and nowhere else. Start thinking of a class as a small unit with a job, not a folder for functions. When you write one, ask what it knows, what it does and what it refuses to let others do.
Common trapwriting classes that are only bags of public fields, while the real rules sit in scattered helper functions that anyone can bypass.
A question to check yourself, an AI practice session and 1 cheat sheet entry come with the full roadmap. Unlock
Resources for this stage
Start with· follow one of these
- CoursePaidGrokking the Object Oriented Design Interview
Design Gurus · Intermediate · Subscription
Its opening chapters teach the four OOP ideas applied inside real designs, with UML and running code
- CourseFreeMIT 6.102: Software Construction
MIT · Intermediate
Free MIT readings: Abstract Data Types, Rep Invariants and Interfaces and Subtyping are this stage at university depth