Java Learning Hub

All courses

720 free lessons across 28 courses. Each lesson has key points, a worked Java example and the pitfalls to avoid; open a course to read its lessons as pages, or pick it above to work through it with visual explainers, labs and a Run button.

• Core Java · 42 lessons
  The Java language itself: types, loops, records, enums, exceptions and java.time.
• OOP · 43 lessons
  Objects, inheritance, interfaces, records and the patterns that hold real Java together.
• Collections · 42 lessons
  Lists, sets, maps and queues — how they work and which one to reach for.
• Streams · 42 lessons
  Turn loops into readable pipelines: filter, map, collect, and parallel work.
• Multithreading · 38 lessons
  Run code in parallel without breaking it: threads, locks, executors, virtual threads.
• JVM · 34 lessons
  How Java really runs: class loading, memory areas, garbage collection and the JIT.
• Java 8 Course · 16 lessons
  The release that changed how Java is written - lambdas, streams and the functional turn.
• Java 21 Course · 15 lessons
  The LTS that made cheap concurrency and real data modelling mainstream.
• Java 23 Course · 15 lessons
  A non-LTS release about direction: gatherers, primitive patterns and a big withdrawal.
• Java 25 Course · 16 lessons
  The LTS where a decade of previews finally landed - and startup became a first-class goal.
• Spring Boot · 39 lessons
  Build a real REST service: beans, config, controllers, JPA, tests and a runnable jar.
• Spring Security · 31 lessons
  Lock down a Spring Boot app: filter chain, JWT, method security and the classic traps.
• Hibernate · 32 lessons
  Map Java objects to SQL tables with JPA and Hibernate, minus the surprises.
• Kafka · 34 lessons
  Topics, partitions, consumer groups and delivery guarantees, with real config.
• Microservices · 33 lessons
  Design, connect and operate services that stay up when one of them falls over.
• Docker · 31 lessons
  Package a Java app into a small, safe container image and run it with confidence.
• Kubernetes · 32 lessons
  Run containers in production: pods, deployments, services, scaling and rollouts.
• System Design · 32 lessons
  Scale, store and ship systems that stay up - and explain them in an interview.
• Kong Course · 15 lessons
  API gateway patterns you learn by sending requests through it, not by reading about it.
• MySQL Course · 21 lessons
  Learn SQL by running it - a real query engine over a real dataset, in the page.
• OAuth 2.0 Course · 13 lessons
  The delegation protocol, walked step by step - who redirects whom, and why.
• JWT Authentication Course · 13 lessons
  What is actually inside a token - decode it, edit a claim, watch verification fail.
• OAuth with Google · 9 lessons
  A guided, end-to-end Google sign-in - the console setup, the real params, the real mistakes.
• GraphQL Course · 14 lessons
  Ask for exactly the fields you need - and watch the response change as you do it.
• Redis Course · 19 lessons
  Model data in Redis, cache without stampedes, lock without lying, and know exactly what a crash costs you.
• Elasticsearch Course · 19 lessons
  Model, index and query text properly - and know why your term query returns nothing.
• RabbitMQ Course · 15 lessons
  Route, acknowledge, retry and dead-letter messages on purpose - and know when Kafka is the better answer.
• Jenkins CI/CD Course · 15 lessons
  Write a Jenkinsfile you would actually ship - triggers, credentials, matrix builds, a Java pipeline and a rollback that works.

Browse all courses and lessons as pages