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.
Master Logback RollingFileAppender with time-based, size-and-time, and fixed-window rolling policies. Includes production-ready logback.xml examples, Spring Boot integration, async logging, and a complete FAQ.
Learn how to mask credit card numbers, SSNs, API keys, and other PII in Logback logs using a custom MaskingConverter, PatternLayout, and logback.xml configuration — with annotated Java code and practical best practices.
A complete implementation of a semantic search engine in pure Java — no external libraries. Covers TF-IDF vectorisation, cosine similarity, and document ranking by meaning. Explains the mathematics behind vector embeddings, how they power RAG and AI search systems, and provides a working query engine with annotated code and sample output. The same architecture used by Pinecone, Weaviate, and Elasticsearch — built from scratch.
A complete, from-scratch implementation of a feedforward neural network in pure Java — no TensorFlow, no DL4J, no external libraries. Covers the Neuron model, forward propagation, sigmoid activation, backpropagation with gradient descent, and trains the network to learn the XOR function. Every line of code is annotated with the underlying mathematics so you understand exactly what the network is doing at each step.
A complete beginner's guide to building a REST API with Spring Boot 3. Covers project setup, clean package structure, a Java record model with Bean Validation, a service layer, a @RestController with GET/POST/PUT/DELETE endpoints, global exception handling with @RestControllerAdvice, and end-to-end curl testing u2014 with fully annotated code throughout.
A complete, reference-level guide to the Java Collections Framework. Covers ArrayList vs LinkedList, HashSet vs LinkedHashSet vs TreeSet, HashMap vs LinkedHashMap vs TreeMap, PriorityQueue, ArrayDeque, and immutable collections u2014 with time-complexity tables, annotated code examples, and a decision guide for choosing the right data structure.