Beginners Guide
17 items
Streams and Collectors
Java Streams API guide: filter, map, flatMap, reduce, collect, groupingBy, parallel streams, and common pitfalls with practical examples.
Modern Java Features
Guide to modern Java features: records, sealed classes, pattern matching, text blocks, var, and a version-by-version feature table from Java 11 to 21.
Optionals
Java Optional guide: creation, chaining, best practices, anti-patterns, and when to use Optional vs null.
Generics
Java Generics guide: generic classes, methods, bounded types, wildcards, PECS principle, type erasure, and common patterns.
Functional Interfaces
Java functional interfaces guide: Function, Predicate, Consumer, Supplier, method references, composition, and writing custom functional interfaces.
Concurrency
Java concurrency guide: threads, ExecutorService, CompletableFuture, virtual threads, thread safety, and common pitfalls.
Collections
Java Collections guide: List, Set, Map deep dive, immutable collections, concurrent data structures, and choosing the right collection.
Error Handling
Java error handling guide: checked vs unchecked exceptions, try-with-resources, custom exceptions, Result/Either pattern, and logging exceptions.
HTTP Clients
Java HTTP client guide: java.net.http HttpClient (sync and async), timeouts, retries, JSON handling, and comparison with OkHttp and Apache HttpClient.
JSON Processing
Java JSON processing guide: Jackson ObjectMapper, annotations, custom serializers, polymorphism, Gson comparison, and common pitfalls.
Testing
Java testing guide: JUnit 5, Mockito mocking, AssertJ fluent assertions, parameterised tests, test patterns, and what to mock vs what not to mock.
Dependency Injection
Dependency injection in Java: constructor injection by hand, why DI matters, the Service Locator anti-pattern, and a brief intro to Spring, Guice, and OSGi.
Maven
Maven guide: POM structure, dependency management, BOM imports, multi-module projects, profiles, useful plugins, and comparison with Gradle.
Logging
Java logging guide: SLF4J facade, Logback and Log4j2 configuration, MDC, structured logging, performance tips, and common pitfalls.