- React – The Component Lifecycle with useEffect
The old three phases map onto one hook. What the dependency array really means, the cleanup function and the requests it cancels, why StrictMode runs your effect twice on purpose, the infinite loop everyone writes once — and the larger point that most effects should not exist at all.
- Java 17 Sealed Classes
A sealed type declares exactly which types may extend it. The compiler enforces the list, and — this is the real payoff — it can then prove that a switch over that type has covered every case. The problem An ordinary interface is open: anyone, anywhere, can implement it. That is usually the point.…
- Recursion
A method that calls itself on a smaller version of the same problem. The base case and the progress towards it, what the call stack is really doing, why StackOverflowError is a message rather than a mystery, and when a loop is the better answer.
- Spring Boot – Elasticsearch
Full-text search that a LIKE query cannot do. Spring Data Elasticsearch repositories, mapping a document, keeping the index in step with the database, and being honest about the operational cost — this is the point where the demo app stops needing only MySQL.
- iOS – SwiftUI Views and Layout
A View is a value, not an object, and almost everything surprising about SwiftUI follows from that. Stacks, frames and the layout conversation between parent and child, modifier order and why it is not decoration, and how to build a reusable container — the card every screen in this app is made of.