Low Level Design Series
Interactive runtime notes

Object-Oriented Programming, from object identity to type bounds

This series starts with the object model, then builds upward through construction, dispatch, encapsulation, and type-safe reuse. Each lesson connects language constructs to memory allocation, runtime behavior, and compile-time contracts.

Study noteThe labs use a pattern-based engine, not a real compiler. That is deliberate: the goal is to train the design intuition and mental model first, then make the code look right in the context of the lesson.
10 labsEngine-checked exercises
05 lessonsIdentity to generics path
OOP mechanicsFrom identity to generics

Lesson Path

Module 01

Objects, State & Identity

The object model, references, identity, value equality, and why mutable state belongs to instances instead of classes.

Open Lab
#identity#shared-state
Module 02

Construction & Ownership

Constructors, `this`, copy lifecycles, private allocation paths, and the rules that keep objects valid as they are created.

Open Lab
#shallow-copy#singleton
Module 03

Runtime Dispatch

Overloading, overriding, vtable routing, inheritance topology, and the way objects collaborate through relationships.

Open Lab
#vtable#relationships
Module 04

Encapsulation & Abstraction

Visibility boundaries, invariant protection, abstract classes, interfaces, and default-method conflict resolution.

Open Lab
#encapsulation#interface-collision
Module 05

Parameterized Polymorphism

Generics, type erasure, wildcard variance, and type-safe reusable containers.

Open Lab
#variance#generic-cache