How the labs work
Java Labs are hands-on coding challenges that take you from the basics to complete projects, one small step at a time.
Every lab compiles and runs Java 8 right in your browser, so there is nothing to install. For each lab:
- Read the task, the input and output rules, and the example.
- Write your code in the editor and press Run to try it.
- Press Check to test it against hidden test cases. Your output must match exactly.
- Stuck? Read the hints, then open Show solution for a full explanation.
Start with the first lab: Hello, World! →
Chapters
- 01 · Output (8 labs)
- 02 · Variables & Types (8 labs)
- 03 · Input & Arithmetic (8 labs)
- 04 · Strings (8 labs)
- 05 · StringBuilder & Characters (8 labs)
- 06 · Conditions (8 labs)
- 07 · Loops (8 labs)
- 08 · Loop Control & Patterns (8 labs)
- 09 · Arrays (8 labs)
- 10 · 2D Arrays (7 labs)
- 11 · Methods (7 labs)
- 12 · Recursion (8 labs)
- 13 · Classes & Objects (7 labs)
- 14 · Inheritance (7 labs)
- 15 · Abstract Classes & Interfaces (7 labs)
- 16 · Exceptions (8 labs)
- 17 · ArrayList (7 labs)
- 18 · Maps & Sets (8 labs)
- 19 · Stacks, Queues & Priority Queues (7 labs)
- 20 · Generics (6 labs)
- 21 · Lambdas & Streams (8 labs)
- 22 · Algorithms (8 labs)
- 23 · Advanced Java (8 labs)
- 24 · Projects (8 labs)