Kotlin Learning Plan 2025: Where to Start for Beginners

Kotlin Learning Plan 2025: Where to Start for Beginners

Kotlin has firmly established itself among the most in-demand programming languages. In 2025, it remains the primary language for Android development, is actively used in backend (Spring Boot, Ktor), and even in cross-platform projects (Kotlin Multiplatform). If you have decided to learn Kotlin from scratch, we have prepared a clear learning plan that will take you from the basics to a confident Junior developer.

Stage 1: Language Basics (2–3 weeks)

Start with the basic syntax and key concepts to write simple programs.

• Variables and Data Types: val, var, basic types (Int, String, Boolean, Double).
• Conditional Statements: if, when (replacement for switch).
• Loops: for, while, repeat.
• Functions: declaration, default parameters, single-expression functions.
• Null Safety: nullable types, operators ?., ?:, !!.
• Collections: lists (listOf, mutableListOf), sets, maps.

Resources: official Kotlin documentation, Kotlin Playground (online sandbox), free course on JetBrains Academy.

Stage 2: Object-Oriented Programming (2–3 weeks)

Kotlin is a language with a powerful OOP model. Master these topics:

• Classes and Objects: constructors, properties, init blocks.
• Inheritance and Interfaces: open classes, abstractions, delegation.
• Data Classes and Enum Classes: for storing data and enumerations.
• Sealed Classes: for restricted type hierarchies.
• Extensions: adding functions to existing classes.

Stage 3: Functional Programming (1–2 weeks)

Kotlin supports a functional style, making code concise and safe.

• Lambda Expressions: higher-order functions, passing lambdas.
• Standard Functions: let, apply, run, also, with.
• Working with Collections: filter, map, flatMap, reduce, groupBy.
• Sequences: lazy evaluation for large data.

Stage 4: Tools and Ecosystem (1–2 weeks)

Without practical tools, learning is incomplete.

• Build Tool: Gradle (learn to configure dependencies).
• IDE: IntelliJ IDEA (Community Edition) or Android Studio.
• Testing: JUnit 5 + Kotest (writing unit tests).
• Version Control: Git, GitHub (basic commands).

Stage 5: First Project and Deepening (2–4 weeks)

Consolidate your knowledge with a real project. Choose one of the directions:

• Android: create a simple app (to-do list, weather) with Jetpack Compose.
• Backend: write a REST API with Spring Boot or Ktor with a database connection.