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Java From Zero to Job-Ready

A Practical Path from First Program to a Tested Spring Boot Backend

A free 41-article course that takes you from your first Java program to a tested, secured Spring Boot and PostgreSQL backend, with three projects, real verified output and interview preparation. Modern Java 21 and later, with older styles labelled.

Start lesson 1 →See all 41 lessons
41
lessons
12
modules
11 h
of reading

Curriculum

12 modules · 41 lessons · about 11 h

Module 1Java Foundations
  1. 01Start Here: What Java Is, How It Runs and Your Roadmap15 min
  2. 02Variables, Types, Operators and Arrays15 min
  3. 03Decisions, Loops, Methods and Scope13 min
Module 2Object-Oriented Java
  1. 04Classes, Objects and Encapsulation12 min
  2. 05Inheritance, Overriding and Overloading11 min
  3. 06Interfaces, Polymorphism and Composition13 min
Module 3Core Java
  1. 07equals, hashCode, toString and the Object Contract12 min
  2. 08Strings, StringBuilder, Text Blocks and Time13 min
  3. 09Enums, Records and Sealed Types12 min
  4. 10Exceptions: Handling Errors Properly12 min
Module 4Collections and Generics
  1. 11Lists and Sets12 min
  2. 12Maps and How HashMap Works14 min
  3. 13Ordering, Queues and Choosing a Collection12 min
  4. 14Generics: Type Safety, Wildcards and Erasure13 min
Module 5Functional Java
  1. 15Lambdas, Functional Interfaces and Method References12 min
  2. 16Streams in Practice (and When Not to Use Them)13 min
  3. 17Null and Optional12 min
Module 6The JVM and Concurrency
  1. 18How the JVM Runs Your Code: Memory, GC and JIT16 min
  2. 19Concurrency Fundamentals: Threads, Races and Synchronisation15 min
  3. 20Executors, Futures, Concurrent Collections and Virtual Threads16 min
Module 7Tools and Craft
  1. 21File I/O and Serialization16 min
  2. 22Debugging: Errors, Stack Traces, the Debugger and Logging18 min
  3. 23Maven: What It Does and How to Use It15 min
  4. 24Git for Java Projects: Commits, Branches, Merging and Pull Requests11 min
  5. 25Testing with JUnit and Mockito: Unit Tests, Mocks and Their Limits16 min
  6. 26Project 1: Build an Expense Tracker CLI in Plain Java29 min
Module 8Databases and JDBC
  1. 27SQL and PostgreSQL Fundamentals for Java Developers21 min
  2. 28JDBC: Talking to a Database from Java25 min
  3. 29Project 2: Move the Expense Tracker to PostgreSQL with JDBC30 min
Module 9Web and Spring
  1. 30HTTP, JSON and REST APIs: How Web Backends Talk20 min
  2. 31Dependency Injection and Inversion of Control: The Idea Behind Spring18 min
  3. 32Spring Boot Foundations: Starters, Auto-Configuration, Properties and Profiles15 min
  4. 33Building a REST API with Spring Boot: Controllers, Services, DTOs, Validation and Errors30 min
Module 10Persistence with JPA
  1. 34JPA and Hibernate: Entities, the Persistence Context, Spring Data and Flyway Migrations29 min
  2. 35JPA Relationships, Lazy Loading, the N+1 Problem, Transactions and Optimistic Locking35 min
Module 11Secure, Tested, Production-Ready
  1. 36Security Fundamentals and Spring Security: Passwords, JWT, Access Control, CORS and Secrets46 min
  2. 37Testing Spring Boot Applications: Slice Tests, MockMvc, Real Databases and the Test Pyramid12 min
  3. 38Production Practices: Configuration, Logging, Docker and Health Checks for Spring Boot9 min
  4. 39Project 3: The Job Application Tracker API, Assembled and Reviewed8 min
Module 12Interviews and Readiness
  1. 40Java Interview Concepts, Part 1: Core Java, Collections, Functional Java, the JVM and Concurrency10 min
  2. 41Java Interview Concepts, Part 2: SQL, Spring, JPA, Security, Testing and the Job-Ready Checklist10 min

This is a free course that takes you from "what is Java?" to a backend you can build, test, secure, run and explain. It is written for beginners who want to become job-ready Java backend developers, and it is deliberately practical: every complete program was compiled and run, every shown output is real, and every project was built and tested.

What you will build

  1. Expense Tracker CLI (article 26): a command-line application with a layered design, file storage, tests and a Maven build.
  2. Expense Tracker on PostgreSQL (article 29): the same domain with JDBC, a connection pool, a repository interface and contract tests against a real database.
  3. Job Application Tracker API (articles 33 to 39): a Spring Boot REST API with JPA, Flyway migrations, JWT login, per-user data access, 125 automated tests, health checks and a Dockerfile.

How it is organised

Twelve modules, 41 articles, each with a "Where this fits" note, exercises with worked solutions, and a "Where to go next" section. Modern Java (21 and later) is the baseline. Older styles that you will meet in existing code are labelled "Older style".

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