100% free · open curriculum

From Zero
to Java Engineer

The complete, interactive path for absolute beginners. No experience needed - just curiosity. Learn the entire Java landscape with real-life analogies, runnable code, and visualizations that actually make things click.

Start Learning - it's free Explore the roadmap

41

Stages

250

Lessons

64h+

Of content

Hello.java

public class Hello {
  public static void main(String[] args) {
    System.out.println("Hello, Java!");
  }
}

$ java Hello
Hello, Java!

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A learning experience built to make things click

Every lesson is designed around how people actually learn - analogy first, then concept, then code you can run.

Real-life analogies first

Every concept starts with something you already understand - a labeled box, a blueprint, a coffee queue - before a single line of code.

Runnable, annotated code

Syntax-highlighted examples with the expected output right there. Copy, paste, run, and see it work.

Interactive visualizations

Watch the stack and heap, a HashMap's buckets, a thread's lifecycle, and a stream pipeline come alive.

Quizzes & progress

Check your understanding after each lesson and watch your progress rings fill as you master each stage.

A real path, not a pile of docs

Seven progressive stages take you from Hello, World! to Spring Boot and system design - in the right order.

English & Deutsch

Learn in the language you think in. The interface and lessons are available in English and German.

The complete Java journey

Every path leads to the same destination: real, job-ready mastery. Pick where you belong and start moving.

☕

Zero to Java Engineer

The complete Java language & platform.

Start from absolute zero. Understand what programming is, what Java is, where it came from, who keeps it alive, and get your machine ready to write your very first program.

8 stages54 lessons16 hours

Start the path

🌿

The Spring Path

From Java engineer to Spring professional.

The heart of the whole ecosystem: the IoC container, beans and their lifecycle, dependency injection, configuration, profiles, and aspect-oriented programming. Master these and the rest of Spring clicks into place.

14 modules90 lessons23 hours

Explore the path

🎯

The Interview Path

From Java engineer to interview-ready.

The foundation every algorithm interview rests on: how to break a problem down, reason about time and space complexity, understand amortized cost, and pick the right data structure - plus the catalog of patterns the rest of the path drills.

9 modules46 lessons11 hours

Explore the path

🏛️

The Architecture Path

From engineer to senior: judgment, not just APIs.

The five SOLID principles as working engineers actually use them - heuristics for code that's easy to change, applied to a messy but real ledger codebase rather than toy examples. Single responsibility, open/closed, Liskov substitution, interface segregation, and dependency inversion - each shown as the fix for a concrete pain.

8 modules48 lessons12 hours

Explore the path

🟣

Kotlin for Java Developers

From Java engineer to polyglot JVM engineer.

Kotlin's superpower for a Java developer is that it isn't a rewrite - it compiles to the same bytecode and calls Java (and is called from Java) seamlessly, so you adopt it one file at a time. The pragmatic case for Kotlin, compiling it alongside Java, calling each way with the interop annotations, the toolchain, and how a real team introduces it into an existing Java codebase.

2 modules12 lessons3 hours

Explore the path

…and every lesson along the way