Java Code Geeks

List<String> and List<Integer> are the exact same class once the JVM gets involved. Here’s why Java made that trade, and what it still costs today. Ask a Java developer to run this quick check, and the answer surprises almost everyone the first time: list1.getClass() == list2.getClass() returns true, even when list1 is a List<String> and list2 is a List<Inte...

Large Language Models are fundamentally stateless. If an application sends the question “What is my favorite programming language?” to a model, the model cannot automatically know that the same user said “My favorite programming language is Java” several requests earlier. Applications therefore need a mechanism for preserving conversational context. Spring AI has traditionally p...

Java 26 just extended AOT caching to ZGC. Before you reach for GraalVM Native Image again, it’s worth asking what that actually changes. For years, “Java starts too slowly for serverless” was simply accepted as fact. Then GraalVM Native Image showed up, compiled Java into a native binary, and became the default answer for anyone …

Same interface, two unrelated types, two completely different rules about what counts as a match. Imagine an interface called Movable, with nothing more exotic than an x coordinate, a y coordinate, and a move operation. Now imagine two classes that have never heard of each other: a Drone and a BoardGamePiece. Both happen to expose an …

Role-Based Access Control (RBAC) is a fundamental security pattern used to restrict system access based on user roles. When combined with JSON Web Tokens (JWT), it enables stateless, scalable, and secure authorization in modern APIs. In this article, we will walk through how to implement RBAC in a Node.js REST API using JWT. 1. RBAC …