A structured Kotlin learning repository that starts with fundamentals and progresses to modern Kotlin 2.x patterns used in production.
- Kotlin:
2.0.21 - Gradle Wrapper:
9.0.0 - JVM Toolchain:
17 - Coroutines:
kotlinx-coroutines-core:1.10.2 - Serialization:
kotlinx-serialization-json:1.8.1 - Tests:
kotlin("test")+ JUnit 5
./gradlew clean build
./gradlew test
./gradlew run
./gradlew runLessonsrunexecutes the modern track entrypoint:modern2026/Modern2026Runner.ktrunLessonsexecutes the root lesson index runner:src/main/kotlin/LessonsRunner.kt
| Track | Focus | Key Files | Level | Estimated Time |
|---|---|---|---|---|
| Foundations | Variables, types, conversions, operators | Variables.kt, BasicTypes.kt, TypeConversion.kt, ArithmeticOperators.kt, AssignmentOperators.kt |
Beginner | 4-6 hours |
| Input & Flow | Console I/O and branching | InputOutput.kt, IfElseIfExpression.kt, ifExpression.kt, When.kt |
Beginner | 3-4 hours |
| Loops & Ranges | Iteration and loop control | ForLoop.kt, WhileLoop.kt, DoWhileLoop.kt, Range.kt, Break.kt, Continue.kt, InOperator.kt |
Beginner | 4-5 hours |
| Functions | Declarations, overloading, recursion, infix, extension | Functions.kt, MethodOverloading.kt, RecursiveFunction.kt, InfixFunction.kt, ExtensionFunction.kt |
Beginner -> Intermediate | 5-7 hours |
| Object-Oriented Kotlin | Classes, constructors, inheritance, interfaces | ClassObjects.kt, Constructor.kt, Inheritance.kt, InterfaceSample.kt, VisibilityModifiers.kt, AbstractClass.kt |
Intermediate | 6-8 hours |
| Data Modeling | Data classes, sealed classes, companion object | DataClass.kt, SealedClass.kt, CompanionObject.kt, OperatorOverloading.kt |
Intermediate | 4-5 hours |
| Modern Kotlin 2026 | Value classes, Result, scope functions, state modeling | modern2026/ValueClassAndTypeSafety2026.kt, modern2026/ResultAndScopeFunctions2026.kt, modern2026/SealedAndDataObject2026.kt |
Intermediate -> Advanced | 4-6 hours |
| Concurrency & Streams | Coroutines, structured concurrency, Flow pipelines | modern2026/CoroutinesFlow2026.kt |
Advanced | 3-4 hours |
| Serialization | Type-safe JSON encode/decode | modern2026/Serialization2026.kt |
Advanced | 2-3 hours |
| Testing | Smoke checks for modern lessons | src/test/kotlin/modern2026/Modern2026SmokeTest.kt |
Intermediate | 2-3 hours |
Total guided time: approximately 37-51 hours.
After finishing the full path, you should be able to:
- Write clear, idiomatic Kotlin for everyday development.
- Model domain states safely with modern Kotlin features.
- Build asynchronous data pipelines with coroutines and Flow.
- Serialize and validate typed JSON payloads.
- Run and verify Kotlin projects with Gradle and tests.
- https://kotlinlang.org/docs/home.html
- https://kotlinlang.org/docs/coroutines-overview.html
- https://kotlinlang.org/docs/serialization.html
- https://github.com/Kotlin/kotlinx.coroutines
- https://github.com/Kotlin/kotlinx.serialization
MIT License