This repository is a structured Kotlin learning project that starts with fundamentals and moves toward modern Kotlin 2.x practices used in production.
- A large set of topic-focused Kotlin source files under
src/main/kotlin/. - A dedicated modern module under
src/main/kotlin/modern2026/. - Gradle Kotlin DSL setup (
build.gradle.kts) with Kotlin 2.x. - Coroutines, Flow, and Serialization examples.
- Test infrastructure with
kotlin("test")+ JUnit 5.
- 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
Run from the project root:
./gradlew clean build
./gradlew test
./gradlew run| Track | Topics | Key Files | Level | Estimated Time |
|---|---|---|---|---|
| Foundations | Variables, types, operators, input/output | Variables.kt, BasicTypes.kt, TypeConversion.kt, Input-Output.kt |
Beginner | 4-6 hours |
| Control Flow | if, when, loops, ranges, branch control |
ifExpression.kt, When.kt, ForLoop.kt, WhileLoop.kt, Range.kt, Break.kt, Continue.kt |
Beginner | 4-5 hours |
| Functions | Function declarations, overloading, recursion, infix, extensions | Functions.kt, MethodOverloading.kt, RecursiveFunction.kt, InfixFunction.kt, ExtensionFunction.kt |
Beginner -> Intermediate | 5-7 hours |
| OOP Core | Classes, constructors, inheritance, interfaces, visibility | Class-Objects.kt, Constructor.kt, Inheritance.kt, InterfaceSample.kt, VisibilityModifiers.kt |
Intermediate | 6-8 hours |
| Modeling | Data classes, sealed hierarchies, companion/object usage | DataClass.kt, SealedClass.kt, CompanionObject.kt |
Intermediate | 3-4 hours |
| Modern 2026 | Sealed interfaces, data object, value class, Result API | modern2026/SealedAndDataObject2026.kt, modern2026/ValueClassAndTypeSafety2026.kt, modern2026/ResultAndScopeFunctions2026.kt |
Intermediate -> Advanced | 4-6 hours |
| Async & Streams | Structured concurrency, suspend, Flow operators |
modern2026/CoroutinesFlow2026.kt |
Advanced | 3-4 hours |
| Data Interchange | JSON encode/decode with kotlinx.serialization | modern2026/Serialization2026.kt |
Advanced | 2-3 hours |
| Validation & Testing | Unit test basics and smoke tests | src/test/kotlin/modern2026/Modern2026SmokeTest.kt |
Intermediate | 2-3 hours |
Total guided time: approximately 33-46 hours.
- Main runner:
src/main/kotlin/modern2026/Modern2026Runner.kt - It runs the complete modern sequence:
- Sealed interface + data object
- Value class + type-safe validation
- Result + scope functions
- Coroutines + Flow
- Serialization
The repository includes smoke tests for the modern lessons.
./gradlew test --info- Finish one curriculum track at a time.
- Run each lesson file and predict output before execution.
- Rewrite examples in your own words and add one custom variation.
- Keep notes on modeling decisions (sealed vs enum vs interface).
- Revisit modern2026 track after fundamentals for deeper understanding.
After completing this repository, a learner should be able to:
- Write clean Kotlin syntax for day-to-day application code.
- Model states and domain rules safely with modern language features.
- Build asynchronous pipelines with coroutines and Flow.
- Serialize and deserialize typed JSON payloads.
- Set up and verify Kotlin code with Gradle + 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