Learn every way to convert LocalDateTime to ZonedDateTime in Java: atZone(), atOffset(), UTC conversion, DST gap and overlap handling, and reverse conversion back to LocalDateTime — with annotated code and a complete reference table.
Build a complete file-upload REST endpoint with Jersey 3.x: single file, multiple files, HTML form testing, curl commands, file-size limits, and a download endpoint. Includes production-hardening tips for cloud storage and MIME validation.
Learn how to add HTTP Basic Auth, JWT Bearer tokens, and role-based access control to Jersey JAX-RS REST APIs. Covers ContainerRequestFilter, SecurityContext, annotations, and Spring Boot integration with annotated Java code.
Build a custom Maven archetype from scratch: create the descriptor, add Velocity-templated source files, install locally, generate a new Spring Boot project from it, and deploy to a team-shared repository. Step-by-step with working code.
Understand the differences between var, let, and const in TypeScript: scope (function vs block), hoisting, the Temporal Dead Zone, re-assignment rules, and TypeScript literal type narrowing — with side-by-side examples and sample output.
Learn how to validate credit card numbers in Java using regular expressions and the Luhn algorithm. Covers Visa, Mastercard, Amex, and Discover patterns, annotated source code, sample output, and JUnit tests.
Master formatting ZonedDateTime in Java with DateTimeFormatter: ISO formatters, custom ofPattern() strings, timezone conversion, parsing, and a full pattern reference table — with annotated code and sample output.
A practical deep dive into Java Message Service (JMS): core concepts, queue vs topic messaging, synchronous and asynchronous consumers, publish-subscribe with Apache ActiveMQ, Spring Boot JmsTemplate, and production best practices.
A complete, from-first-principles guide to Java's Comparable and Comparator: natural vs. external ordering, the comparing/thenComparing/reversed chaining API, nullsFirst/nullsLast, TreeSet, records as sort keys (and the equals-consistency trap they create), and a real reproduction of the integer-subtraction-overflow comparator bug with a failing test, not just a warning. Every example runs against a companion repository.
Learn how to use Java BufferedReader to read files line by line, read console input, stream lines with Java 8, and choose between BufferedReader, Scanner, and Files.readAllLines(). Includes annotated code examples and a methods reference table.