50 interactive exercises — right in your browser

Learn Java.
No setup.

Write code, run it, see the result — all on one page. No JDK, no IDE, no bullshit.

Start the first exercise Playground How does it work?
Basics
Hello, World!
void main() { // Your code here IO.println("Hello, World!"); }
Run Test passed
Why java-hell

Everything you need.
Nothing that distracts you.

No account, no download, no video you watch at 2x speed. Just you and the code.

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Editor in your browser

A code editor with Java syntax highlighting and a theme that doesn't burn your eyes.

>_

Real compilation

Your code is compiled and run on a server. Real error messages, real Java.

✓

Automatic tests

Every exercise has tests. You know instantly whether your solution works — no guessing, no hoping.

☰

50 exercises

From Hello World to inheritance. Each one builds on the last, with rising difficulty.

🔑

No login

Your progress is saved locally. No email, no password, no newsletter.

😈

Nibbi has your back

Nibbi, your little devil, nibbles at your bugs: cheers with you and points at the broken line after three failed tries. Plus, every exercise has a hint you can unfold.

Topics

Java exercises by topic.

Want to practice loops, arrays or exceptions specifically? Pick a topic and jump right in.

First Steps Hello World, printing, math 6 exercises Variables int, double, String, boolean 6 exercises If-Else if, else, else-if, comparisons 4 exercises Loops for, while, countdown, modulo 5 exercises Arrays index, length, looping 4 exercises Methods parameters, return values 4 exercises Strings & Switch length(), equals(), switch 3 exercises Classes & Objects classes, constructors, inheritance 4 exercises Exceptions try, catch, finally 4 exercises User Input IO.readln, parsing input 2 exercises Practice Problems profile card, calculator, FizzBuzz 7 exercises
The path

From zero to Java — in two phases.

First you learn the language in your browser. Then we show you how to set up your own environment.

Phase 1: Browser

50 exercises right here on the page. Variables, loops, arrays, methods, OOP — everything you need to get started. No setup required.

~ 2-4 hours

Phase 2: IDE

You set up IntelliJ IDEA or VS Code. We show you how, step by step — with screenshots and without jargon.

To the guide →

Phase 3: Your own projects

You build your first programs of your own. CLI tools, small games, APIs — whatever interests you.

Coming soon

Ready?

The first exercise takes 30 seconds. After that, you decide whether to keep going.

Let's go