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Kotlin Core Programming

Master Kotlin language fundamentals, advanced features, and modern programming paradigms from basics to expert level

Beginner to AdvancedSelf-paced14 modules110 available lessons

Your path, one skill at a time.

Kotlin is a modern, expressive programming language that combines object-oriented and functional programming features. This roadmap covers everything from basic syntax to advanced language features like value classes, DSLs, contracts, and Kotlin Multiplatform. Build a solid foundation in Kotlin that serves Android, backend, and multiplatform development.

What you’ll learn

  • Write idiomatic and expressive Kotlin code
  • Master functional programming concepts in Kotlin
  • Understand and use advanced language features (value classes, contracts, context parameters)
  • Build type-safe domain-specific languages (DSLs)
  • Implement asynchronous programming with coroutines (intro here; deep dive in Coroutines course)
  • Use Kotlin reflection and metaprogramming
  • Apply design patterns and best practices
  • Develop Kotlin Multiplatform applications

THE CURRICULUM

Build your knowledge, step by step.

110 lessons across 14 modules. Open a module to explore its lessons and practical work.

01MODULE 01Kotlin Basics and Syntax8 lessons · Self-paced

Foundation concepts, basic syntax, and getting started with Kotlin

  1. 01Kotlin Introduction and Setup (K2 compiler, IntelliJ/AS)15 min
  2. 02Variables and Data Types15 min
  3. 03val vs var and Immutability15 min
  4. 04String Templates and Operations15 min
  5. 05Basic Input/Output Operations15 min
  6. 06Comments and KDoc Basics15 min
  7. 07Kotlin vs Java (syntax & semantics quick tour)15 min
  8. 08Practice: Basic Kotlin Programs45 min
02MODULE 02Control Flow and Functions7 lessons · Self-paced

Control structures, function declarations, and program flow

  1. 01if Expressions and when Statements15 min
  2. 02Loops: for, while, do-while15 min
  3. 03Ranges and Progressions15 min
  4. 04Functions: parameters, defaults, named args15 min
  5. 05Single-Expression Functions15 min
  6. 06Return and Jump Expressions15 min
  7. 07Practice: Control Flow Exercises40 min
03MODULE 03Null Safety and the Type System8 lessons · Self-paced

Kotlin's null safety and core type-system features

  1. 01Nullable vs Non-nullable Types15 min
  2. 02Safe Calls, Elvis, and let15 min
  3. 03Not-null Assertion (!!) — why to avoid it15 min
  4. 04Smart Casts and is-checks15 min
  5. 05Scope Functions: run, with, apply, also15 min
  6. 06Type Checking & Casting, Nothing/Unit/Any quick tour15 min
  7. 07Null-Safety Best Practices15 min
  8. 08Practice: Null-Safety Implementation35 min
04MODULE 04Object-Oriented Programming11 lessons · Self-paced

Classes, objects, inheritance, and OOP principles in Kotlin

  1. 01Classes and Objects Basics15 min
  2. 02Primary & Secondary Constructors; init15 min
  3. 03Properties and Custom Accessors15 min
  4. 04Inheritance, open/final, and Overriding15 min
  5. 05Abstract Classes and Interfaces (incl. sealed interfaces)15 min
  6. 06Visibility Modifiers15 min
  7. 07Data Classes & Data Objects (Kotlin 1.9+)15 min
  8. 08Sealed Classes & Exhaustive when15 min
  9. 09Object Declarations, Companion Objects15 min
  10. 10Nested and Inner Classes15 min
  11. 11Practice: OOP Design Patterns60 min
05MODULE 05Collections and Data Structures10 lessons · Self-paced

Working with collections, sequences, and data manipulation

  1. 01Arrays and Array Operations15 min
  2. 02Lists: Mutable vs Read-only15 min
  3. 03Sets and Maps Overview15 min
  4. 04Collection Operations: filter/map/reduce15 min
  5. 05Sequences for Lazy Evaluation15 min
  6. 06Grouping, Partitioning, Windowing15 min
  7. 07Sorting and Searching15 min
  8. 08Custom Collection Operations15 min
  9. 09Performance Considerations & immutability tips15 min
  10. 10Practice: Data Processing Pipeline50 min
06MODULE 06Functional Programming8 lessons · Self-paced

Functional concepts, higher-order functions, and inline performance

  1. 01Higher-Order Functions & Function Types15 min
  2. 02Lambdas & Anonymous Functions (with receiver)15 min
  3. 03Closures and Captured Variables15 min
  4. 04inline/noinline/crossinline & performance15 min
  5. 05Function Composition & Partial Application15 min
  6. 06Tail Recursion (tailrec)15 min
  7. 07Functional Patterns in Kotlin (Option/Result style)15 min
  8. 08Practice: FP Challenges55 min
07MODULE 07Exception Handling and Error Management7 lessons · Self-paced

Exceptions, Result type, and defensive programming

  1. 01Exception Hierarchy in Kotlin15 min
  2. 02try/catch/finally Patterns15 min
  3. 03Throwing & Custom Exceptions15 min
  4. 04Result & runCatching; error mapping15 min
  5. 05Best Practices (checked vs unchecked mindset)15 min
  6. 06Defensive Programming Techniques15 min
  7. 07Practice: Robust Error Handling35 min
08MODULE 08Generics and Type Parameters8 lessons · Self-paced

Generic programming, constraints, and variance

  1. 01Generic Classes and Functions15 min
  2. 02Type Parameters and where-Constraints15 min
  3. 03Variance: in/out (use-site & declaration-site)15 min
  4. 04Star Projections & Type Projections15 min
  5. 05Reified Type Parameters & inline15 min
  6. 06Type Inference tips & pitfalls15 min
  7. 07Best Practices with Generics15 min
  8. 08Practice: Generic Data Structures45 min
09MODULE 09Coroutines and Async Programming (Language Intro)5 lessons · Self-paced

Language-level intro so you can read coroutine code; the full deep-dive is a separate course.

  1. 01Coroutines Fundamentals (suspend, builders, scopes)15 min
  2. 02Dispatchers & withContext (overview)15 min
  3. 03Flows at a Glance (cold vs hot)15 min
  4. 04Exceptions & Cancellation — quick rules15 min
  5. 05Practice: Async tasks with structured concurrency45 min
10MODULE 10Advanced Language Features9 lessons · Self-paced

Modern Kotlin features you’ll actually use

  1. 01Extension Functions & Properties15 min
  2. 02Operator Overloading (do’s & don’ts)15 min
  3. 03Delegated Properties & patterns (lazy, observable, vetoable)15 min
  4. 04Type Aliases & Destructuring15 min
  5. 05Value Classes (a.k.a. inline classes) + @JvmInline15 min
  6. 06Contracts (opt-in): callsInPlace, returns15 min
  7. 07Context Parameters (replacing context receivers) — status & examples15 min
  8. 08Annotations & Annotation Processing (kapt/ksp overview)15 min
  9. 09Practice: Advanced Feature Implementation55 min
11MODULE 11DSL Creation and Metaprogramming7 lessons · Self-paced

Type-safe builders, receivers, and @DslMarker

  1. 01DSL Design Principles15 min
  2. 02Function Literals with Receiver15 min
  3. 03Type-Safe Builders & nested scopes15 min
  4. 04DSL Scope Control with @DslMarker15 min
  5. 05HTML/SQL DSL Examples15 min
  6. 06DSL Testing & Docs15 min
  7. 07Practice: Custom DSL Development50 min
12MODULE 12Reflection and Runtime Features7 lessons · Self-paced

Kotlin reflection API and runtime type info

  1. 01Reflection Basics & KClass15 min
  2. 02Property & Function Reflection15 min
  3. 03Callable References15 min
  4. 04Runtime Annotation Processing (brief)15 min
  5. 05Reflection Performance & alternatives15 min
  6. 06Reflection Use Cases & pitfalls15 min
  7. 07Practice: Reflection-Based Utilities40 min
13MODULE 13Testing in Kotlin8 lessons · Self-paced

Testing strategies and frameworks

  1. 01Unit Testing Fundamentals15 min
  2. 02JUnit 5 with Kotlin15 min
  3. 03kotlin.test & Assertions15 min
  4. 04Mocking with MockK15 min
  5. 05Property-Based Testing (Kotest/quickcheck)15 min
  6. 06Testing Coroutines (pointer to the full course)15 min
  7. 07TDD workflow in Kotlin15 min
  8. 08Practice: Comprehensive Test Suite50 min
14MODULE 14Best Practices and Code Quality7 lessons · Self-paced

Conventions, performance, and professional practices

  1. 01Kotlin Coding Conventions & Style15 min
  2. 02Static Analysis with Detekt & ktlint15 min
  3. 03Performance: allocations, boxing, inline/value classes15 min
  4. 04Memory & GC basics (JVM/Native notes)15 min
  5. 05Opt-in APIs: @RequiresOptIn / @OptIn and stability levels15 min
  6. 06Kotlin Evolution & K2 Migration Tips15 min
  7. 07Capstone: Advanced Kotlin Application90 min