Java 21 was the biggest LTS since Java 8, and Java 25 (LTS, September 2025) finalizes most of the preview features that shipped alongside it. If you last touched modern Java during the Java 17 era, the jump to 25 is not just a syntax refresh — it fundamentally changes how you write concurrent code, pattern-match data, and model domain objects. This post walks through the six features that matter most for day-to-day Java work, with runnable code for each.
Continue reading Java 21 to Java 25 LTS: Every Feature You Actually Need to KnowAI Prompts Playbook: Upgrading Java 8 → 11 → 17 → 21 → 25
Most Java codebases in production today are still on Java 8, 11, or 17. Upgrading captures years of ecosystem improvements — but the work is tedious, repetitive, and easy to get wrong. This post is a copy-paste playbook of AI prompts (works in Claude, ChatGPT, Gemini, or Cursor) that take you stage-by-stage through every LTS jump: 8→11, 11→17, 17→21, and 21→25. Each prompt is described so you know exactly what it does and when to reach for it.
Continue reading AI Prompts Playbook: Upgrading Java 8 → 11 → 17 → 21 → 25Modern Java Testing: JUnit 6 + AssertJ + Mockito 5 + Testcontainers
JUnit 6 is the first major JUnit release built for Java 17+ and the virtual-thread era. But JUnit alone is only the runner — modern Java test suites pair it with AssertJ for fluent assertions, Mockito 5 for mocking, and Testcontainers for real infrastructure in integration tests. This post ties all four together into a complete, runnable example you can drop into any Spring Boot or plain-Java project.
Continue reading Modern Java Testing: JUnit 6 + AssertJ + Mockito 5 + TestcontainersJava Concurrency Deep Dive: CompletableFuture, ExecutorService, ForkJoinPool with Examples
Even in the age of virtual threads, the classic Java concurrency toolbox — ExecutorService, CompletableFuture, and ForkJoinPool — is not going anywhere. Each one solves a different problem, and picking the wrong one is a common source of latency bugs. This post walks through all three with runnable examples, then adds AI prompts to review and refactor your own concurrent code.
Java Streams API Deep Dive + Collectors Cookbook
The Stream API turned ten years old with Java 18, and the Collectors utility class has quietly grown into one of the most powerful data-transformation toolkits in the JDK. This post is a working cookbook: the patterns you actually reach for in production code, each with a runnable snippet and an explanation of why it works. A set of AI prompts at the end will help you refactor imperative loops into clean pipelines automatically.
Java 21 to Java 25 Upgrade Guide (with AI Prompts)
Java 25 shipped as an LTS release in September 2025. If you are already on Java 21 LTS, the jump is mostly smooth — most new features were previews in 21 that are now final — but there are a handful of deprecations, build-tool bumps, and behavioural tweaks that will trip you up if you do not prepare. This guide walks through the upgrade end-to-end with a migration checklist and AI prompts to automate the tedious parts.
Continue reading Java 21 to Java 25 Upgrade Guide (with AI Prompts)Adding Two Integers in Java – 5 Practical Approaches with Examples
Adding two integers is the “Hello, World” of arithmetic in Java — but a truly useful beginner guide goes far beyond a single line of code. In this post you will learn five distinct ways to add two integers in Java: hardcoded literals, Scanner console input, command-line arguments, method parameters, and streams. Along the way you will understand integer overflow, the difference between int and long, and how to guard against bad input.