- Java 21 Record Patterns
A record pattern matches a record and pulls its components out in the same step. It is a small piece of syntax that removes the accessor calls from every branch of a type switch , and it composes to arbitrary depth. It only works on records , and that is not an arbitrary restriction. A record…
- Backend Dev – Get Started
Start here. What a backend engineer builds, the ten things you need to learn and the order to learn them in, and the exact stack every example in this track uses — Java 21 and Spring Boot 4.1. Also: how this track fits with the deeper ones on the site, so you know when to stop reading here and go read those instead.
- Binary Search
Halve the search space every comparison: O(log n), a billion elements in thirty steps. Also the three ways it is habitually got wrong — the midpoint overflow that was in the JDK for nine years, the infinite loop, and the boundary — plus lowerBound, the variant that is actually useful.
- Spring Boot – Method-Level Security
@PreAuthorize, @PostAuthorize and @Secured, and why URL rules alone stop being enough as soon as two entry points reach the same service. Expression-based checks against the authenticated principal, and the proxy rule that makes an internal call skip the check entirely.
- Python – OOP
Inheritance, composition and polymorphism in a language with duck typing, where an interface is a set of methods rather than a declaration. `super()`, properties, abstract base classes, and when to prefer composition.