Learn Java by writing real Java

Every exercise is compiled by the real javac 21 compiler and run by a Java virtual machine, both inside your browser, on your own device. The lessons of Java Programming I and II follow the University of Helsinki's Java Programming MOOC, with their own explanations and exercises; the extra modules after them are Java Arena's own.

All 59 modules are online: 54 following the MOOC (Java Programming I and II) and 5 extra modules of Java Arena's own, with 359 steps and 1077 challenges.

Module 1: Printing
Module 2: Reading input and strings
Module 3: Variables and types
Module 4: Calculating with numbers
Module 5: Making decisions
Module 6: Conditions and logic
Module 7: Problem-solving patterns
Module 8: Repeating with while
Module 9: Loop conditions and for
Module 10: Methods and parameters
Module 11: Return values and the call stack
Module 12: Finding bugs
Module 13: Lists
Module 14: For-each, list methods and lists in methods
Module 15: Arrays
Module 16: Working with strings
Module 17: Classes and objects
Module 18: Getters, toString and bigger classes
Module 19: Objects in a list
Module 20: Reading files
Module 21: Designing classes and overloading
Module 22: Primitive and reference variables
Module 23: Objects working together
Module 24: Lists inside objects
Module 25: Separating the UI from program logic
Module 26: Troubleshooting and unit testing
Module 27: Procedural and object-oriented programs
Module 28: Sorting and searching
Module 29: Larger programs
Module 30: Warm-up: recap of parts 1 to 7
Module 31: Hash maps
Module 32: Comparing objects: equals and hashCode
Module 33: Grouping data with hash maps
Module 34: Inheritance and abstract classes
Module 35: Interfaces
Module 36: Polymorphism
Module 37: Streams and lambdas
Module 38: Ordering objects: Comparable and Comparator
Module 39: StringBuilder, regular expressions, enums and iterators
Module 40: Class diagrams
Module 41: Packages and imports
Module 42: Exceptions
Module 43: Writing files
Module 44: Type parameters (generics)
Module 45: Building your own list and hash map
Module 46: Random numbers
Module 47: Two-dimensional arrays
Module 48: GUI: windows, components and layouts
Module 49: GUI: event handling
Module 50: GUI: multiple views
Module 51: Data visualization
Module 52: Drawing, images and sound
Module 53: Project: an Asteroids-style game
Module 54: Libraries, Maven and databases
Module 55: Recursion Extra
Module 56: Records Extra
Module 57: switch, var and text blocks Extra
Module 58: Pattern matching and sealed types Extra
Module 59: Linked lists, stacks, queues and trees Extra
All modules

Practice: Deathmatch drills, the daily challenge and a placement quiz.

Projects: larger programs built over several milestones.

Pro Track: after the course, projects to build on your own computer with a JDK 21, Maven and JUnit 5 tests.