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A calm, thorough guide to immutability as a software design principle: the sealed-photograph vs. editable-document analogy, the formal definition (immutable object vs. unchangeable variable), a direct mutable-vs-immutable comparison table, the historical origins in 1950s functional programming and Java’s immutable String, a side-by-side building-blocks diagram of shared mutable vs. shared immutable…
A complete, friendly guide to the Value Object pattern from domain-driven design: the coin-versus-passport analogy, the formal definition and its 2002 Fowler / 2003 Evans origins, side-by-side comparison with entities, the four defining traits (equality by value, immutability, no identity, self-validation), a worked Money code example contrasting raw primitives with…
A complete guide to the Composition Over Inheritance design principle: the LEGO-and-costume-shop analogy, the formal definition and its Gang of Four origins with a fair acknowledgment of the original nuance, the fragile base class problem illustrated with the classic Bird-Penguin example, a full has-a versus is-a comparison, a step-by-step build…
A complete guide to the Spaghetti Code anti-pattern: the tangled-plate-of-spaghetti analogy, the formal definition (tangled control flow, structure not correctness), the historical origin in the GOTO instruction and Dijkstra 1968 letter “Go To Statement Considered Harmful,” the four common causes (deadline pressure, no upfront design, many hands without coordination, missing…
A complete guide to Dependency Injection (DI) as a software design principle: the lamp / bulb / socket analogy, its formal definition and relationship with Inversion of Control, the tight-coupling problem it solves (with a before / after order-confirmation example), the three roles involved (Client, Service, Injector), a step-by-step build…
Both promise a set of actions before any details are filled in. Both stop you from creating an object directly from them. So why do object-oriented languages bother offering both? This thirteen-chapter guide unpacks what each one really is, five side-by-side differences, a small Vehicles-and-Rechargeable code example, whether a class…
Four ideas hold up almost every large piece of software you have ever used — encapsulation, abstraction, inheritance, and polymorphism. They sound technical, but underneath, they are just clever ways of organising things. This twelve-chapter guide walks through what OOP itself really is, the difference between classes and objects, each…
Why write the same thing twice when one class can simply borrow it from another? Inheritance lets related pieces of code share what they have in common — while each one still keeps what makes it special. This thirteen-chapter guide walks through what inheritance really is, the “is-a” relationship, how…
One instruction, delivered to different objects, produces different but each perfectly appropriate results. That is the entire secret behind polymorphism — one of programming’s most useful ideas. This thirteen-chapter guide unpacks what the word literally means (Greek for “many forms”), what polymorphism really is in code, why it matters, the…
Encapsulation bundles data and the actions that work on it into one protected unit, then hides the messy inner details from everyone else. This twelve-chapter guide walks through what it really is, why every serious project relies on it, the four ingredients of a capsule, how it differs from abstraction…