A beginner-to-advanced guide to migrating off Undertow on Spring Boot 4: why it was dropped (Jakarta EE 11 / Servlet 6.1), the real Maven error and runtime NoSuchMethodError you get if you fight it, Tomcat 11 tuning, and a verified working Jetty 12.1 alternative — all tested on a real Spring Boot 4.1 app.
A beginner-to-advanced guide to Spring Framework 7's built-in API versioning: the version attribute, baseline versions, the supported-versions gotcha, RFC-compliant deprecation headers, client-side ApiVersionInserter, and testing — verified against a real running Spring Boot 4.1 app.
A beginner-to-advanced guide to Micrometer and Spring Boot 4's new spring-boot-starter-opentelemetry: what actually changed (it isn't "Micrometer 2"), the Observation API, context propagation gotchas, a runnable cardinality-explosion demo, and a full migration checklist.
Beyond the standard strlen/struct tutorials: real, runnable FFM API examples for upcalls (C calling back into Java), capturing errno with Linker.Option.captureCallState, measured downcall overhead, and a practical guide to JEP 472's JNI/FFM lockdown — including live jnativescan output. JDK 22-26.
Why 0.1 + 0.2 isn't 0.3, when double is fine, when BigDecimal is mandatory, and when fixed-point long is fastest. A beginner-to-advanced guide to number precision in Java — with runnable code, real output, a benchmark, rounding modes, MathContext, and a decision table.
A practical Spring Framework 6 to 7 migration guide covering the Jakarta EE 11 baseline, removed and deprecated APIs, AOT and GraalVM changes, BeanRegistrar and proxy lifecycle changes, JSpecify null safety, testing and security implications, an upgrade checklist, and an AI prompt to scan your project.
A beginner-to-advanced guide to structured concurrency in Java (JDK 25/26). Learn StructuredTaskScope, Joiners (allSuccessfulOrThrow, anySuccessfulOrThrow, race), timeouts, custom joiners, failure handling, thread-dump observability, and how it compares to CompletableFuture — with runnable code, real output, and a diagram.
Learn the Interpreter design pattern in Java by building a working math expression evaluator. Understand abstract syntax trees, terminal vs. non-terminal expressions, and where this pattern appears in SQL engines, regex, and Spring SpEL.
Complete reference for all 23 Gang of Four design patterns implemented in Java 17. Each pattern has a dedicated post with beginner-to-advanced coverage, full runnable code, UML diagram, and console output. Creational, Structural, and Behavioral patterns with real-world examples and JDK cross-references.
The Visitor pattern lets you add new operations to a class hierarchy without modifying it. Each operation is a separate Visitor class; elements accept visitors via double dispatch. Complete Java guide: shape hierarchy with AreaCalculator and PerimeterCalculator visitors, double dispatch explained, when Visitor beats a switch statement, and when it's overkill.