The Complete Kotlin Course
A zero-to-advanced Kotlin curriculum: from your very first line of code through Kotlin's celebrated null safety, functional and object-oriented programming, collections and generics, coroutines, and the idioms used in real Android and backend projects.
Phase 1 · Foundations
Setup, syntax, null safety, control flow, functions, strings.
Introduction to Kotlin
What Kotlin is, why it exists, how it runs, and writing your first program — the concise, modern language behind Android.
Variables, Types & Basic Syntax
Store data with val and var, Kotlin's type system, and readable string templates.
Null Safety
Kotlin's flagship feature — eliminate null-pointer errors with nullable types and safe operators.
Operators, Ranges & Type Checks
Operators, equality, ranges, and Kotlin's smart casts.
Control Flow
Make decisions with if and the powerful when expression, and loop over ranges and collections.
Functions
Declare expressive functions with default and named arguments, single-expression bodies, and varargs.
Strings & Console I/O
Master string templates, multiline strings, and reading input from the console.
Phase 2 · Functions & Functional
Lambdas, collection operations, scope functions, extensions.
Lambdas & Higher-Order Functions
Treat functions as values with lambdas and higher-order functions — the heart of functional Kotlin.
Collection Operations
Transform data declaratively with map, filter, fold, groupBy, and Kotlin's rich collection API.
Scope Functions
let, run, with, apply, and also — the small functions that make Kotlin so expressive.
Extension Functions & Properties
Add methods and properties to existing types — even ones you don't own.
Function Types, Inline & References
Store and pass functions, and understand inline functions and reified types.
Phase 3 · Object-Oriented Kotlin
Classes, data classes, inheritance, interfaces, sealed classes.
Classes & Constructors
Define classes with Kotlin's concise primary constructors and init blocks.
Properties, Getters & Backing Fields
Kotlin properties with custom accessors, backing fields, and lateinit.
Data Classes
Boilerplate-free data holders with generated equals, hashCode, toString, and copy().
Inheritance & Interfaces
Extend classes with open/override and design contracts with interfaces.
Objects, Companion Objects & Singletons
Singletons and factories with object declarations and companion objects.
Sealed Classes & Enums
Model restricted hierarchies and states with enums and sealed classes — perfect with when.
Visibility, Nested & Inner Classes
Control access with visibility modifiers and organize code with nested and inner classes.
Phase 4 · Collections & Generics
Collections, sequences, generics, delegation.
Collections in Depth
Read-only vs mutable Lists, Sets, and Maps, and how to choose between them.
Sequences
Process large data lazily and efficiently with sequences.
Generics
Write type-safe, reusable code with generics and Kotlin's variance (in/out).
Delegation & Delegated Properties
Reuse behavior with class delegation and powerful delegated properties like lazy.
Phase 5 · Advanced Kotlin
Operator overloading, destructuring, exceptions, reflection, DSLs.
Operator Overloading & Conventions
Give your types natural syntax with operator functions and infix conventions.
Destructuring, Type Aliases & Idioms
Unpack values elegantly and write idiomatic, concise Kotlin.
Exceptions & Error Handling
Handle failure idiomatically with try as an expression, Result, and sealed error types.
Annotations & Reflection
Add metadata with annotations and inspect code at runtime with reflection.
Domain-Specific Languages (DSLs)
Build expressive, type-safe DSLs using lambdas with receivers — a Kotlin superpower.
Functional Kotlin
Embrace immutability, function composition, and functional error handling with Arrow.
Phase 6 · Coroutines & Async
Coroutines, dispatchers, structured concurrency, flows, channels.
Coroutines Fundamentals
Write asynchronous, non-blocking code with suspend functions and coroutine builders.
Coroutine Context, Dispatchers & Scopes
Control where and how coroutines run with dispatchers and scopes.
Structured Concurrency & Cancellation
Manage coroutine lifecycles, cancellation, and errors the structured way.
Flows
Handle streams of asynchronous data with cold Flows and StateFlow/SharedFlow.
Channels & Shared State
Communicate between coroutines with channels and manage shared state safely.
Phase 7 · Professional & Applied
Java interop, testing, build tools, Android, multiplatform, workflow.
Java Interoperability
Mix Kotlin and Java seamlessly in the same project.
Testing
Prove your code works with JUnit 5, Kotest, and MockK — including coroutines and flows.
Build Tools & the Ecosystem
Build and manage projects with Gradle and the Kotlin DSL.
Kotlin for Android
Why Kotlin owns Android — project structure, lifecycle, and Jetpack Compose.
Kotlin Multiplatform & Native
Share code across iOS, Android, JVM, and more with Kotlin Multiplatform.
Clean Code, Idioms & Professional Workflow
Write idiomatic Kotlin and collaborate professionally with Git and CI.
Phase 8 · Portfolio
Progressively larger capstone projects.