Kotlin for Beginners: Your First App, Step-by-Step

Want to build powerful Android apps or server-side applications? Learning Kotlin, a modern programming language, is your ticket. But where do you begin? This guide provides a practical, step-by-step approach to getting started with Kotlin, even if you’re a complete beginner. Are you ready to write your first Kotlin program?

1. Install the Java Development Kit (JDK)

Kotlin compiles to bytecode that runs on the Java Virtual Machine (JVM). Therefore, you need a Java Development Kit (JDK). I recommend using a recent version, like JDK 17 or later, for the best compatibility and performance. You can download the JDK from Oracle’s website or use an open-source distribution like Eclipse Temurin.

Pro Tip: After installation, ensure the JAVA_HOME environment variable is set correctly and that the bin directory of your JDK installation is added to your system’s PATH. This allows you to run Java and Kotlin commands from any terminal.

2. Choose an Integrated Development Environment (IDE)

An Integrated Development Environment (IDE) makes coding much easier. For Kotlin, I strongly recommend IntelliJ IDEA. It’s developed by JetBrains, the same company behind Kotlin, and offers excellent support for the language, including code completion, debugging, and refactoring. The Community Edition is free and sufficient for most beginners. Alternatively, you can use Android Studio, also based on IntelliJ IDEA, if you plan to develop Android apps.

Common Mistake: Don’t try to learn Kotlin with a basic text editor. An IDE provides essential features that significantly speed up your learning process and prevent common errors.

3. Install the Kotlin Plugin in IntelliJ IDEA

If you’re using IntelliJ IDEA, you need to install the Kotlin plugin. Here’s how:

1. Open IntelliJ IDEA.
2. Go to File > Settings (or IntelliJ IDEA > Preferences on macOS).
3. Select Plugins.
4. Search for “Kotlin” in the Marketplace tab.
5. Click Install.
6. Restart IntelliJ IDEA when prompted.

Pro Tip: Keep the Kotlin plugin updated to the latest version to benefit from new features and bug fixes. Check for updates regularly in the Plugins settings.

4. Create Your First Kotlin Project

Now, let’s create your first Kotlin project:

1. Open IntelliJ IDEA.
2. Click New Project.
3. In the New Project window, select Kotlin in the left panel.
4. Choose JVM | IntelliJ as the project template.
5. Give your project a name (e.g., “HelloKotlin”) and specify a location.
6. Click Create.

IntelliJ IDEA will create a new project structure with a src directory where you’ll put your Kotlin code.

5. Write Your First Kotlin Code

Inside the src directory, create a new Kotlin file (e.g., Main.kt). Right-click on the src directory, select New > Kotlin Class/File, and choose File. Then, add the following code:

fun main() {
    println("Hello, Kotlin!")
}

This simple program defines a main function, which is the entry point of your application, and prints “Hello, Kotlin!” to the console.

Common Mistake: Kotlin is case-sensitive. Make sure you use the correct capitalization for keywords like fun and println.

6. Run Your Kotlin Program

To run your program, right-click in the code editor and select Run ‘MainKt’. Alternatively, you can click the green “play” button in the gutter next to the main function. IntelliJ IDEA will compile and execute your code, and you should see “Hello, Kotlin!” printed in the console.

7. Learn Basic Kotlin Syntax

Now that you’ve run your first Kotlin program, it’s time to learn some basic syntax. Here are a few key concepts:

• Variables: Declare variables using val (read-only) or var (mutable). For example: val name: String = "Alice" or var age: Int = 30.
• Functions: Define functions using the fun keyword. For example: fun add(a: Int, b: Int): Int = a + b.
• Data Types: Kotlin has built-in data types like Int, Double, Boolean, and String.
• Control Flow: Use if, else, when, for, and while statements for control flow.
• Classes: Define classes using the class keyword. For example: class Person(val name: String, var age: Int).

Pro Tip: Explore the official Kotlin documentation for a comprehensive overview of the language syntax and features. It’s the best resource for understanding Kotlin in depth.

8. Practice with Kotlin Koans

Kotlin Koans are a series of interactive exercises that teach you Kotlin concepts through hands-on practice. They’re a great way to reinforce your learning and discover new features of the language. You can access Kotlin Koans directly within IntelliJ IDEA. Go to Tools > Kotlin Koans > Open Kotlin Koans.

Case Study: We recently used Kotlin Koans to onboard a new junior developer at our firm, Data Solutions Group, located near the Georgia Tech campus in Atlanta. Within two weeks, they were able to contribute meaningfully to our Kotlin-based backend services. Before Koans, it took nearly a month for new hires to become productive. The exercises provide immediate feedback and cover a wide range of topics, from basic syntax to advanced concepts like coroutines.

9. Build a Simple Project

The best way to learn a new programming language is to build something with it. Choose a simple project that interests you, such as a command-line calculator, a to-do list application, or a simple game. Break the project down into smaller tasks and tackle them one by one. Don’t be afraid to experiment and make mistakes – that’s how you learn!

Editorial Aside: Here’s what nobody tells you: your first few projects will probably be messy. That’s fine! The goal is to learn, not to write perfect code from the start. Focus on understanding the concepts and getting things working. You can always refactor and improve your code later.

10. Explore Kotlin Libraries and Frameworks

Kotlin has a rich ecosystem of libraries and frameworks that can help you build various types of applications. Some popular options include:

• Ktor: A framework for building asynchronous server-side applications.
• Arrow: A library for functional programming in Kotlin.
• Android Jetpack: A suite of libraries for building modern Android apps.
• Kotlin/Native: Compile Kotlin to native binaries for various platforms, including iOS, macOS, and Linux.

Choose a library or framework that aligns with your project goals and start exploring its features. The official documentation and online tutorials are valuable resources for learning how to use these tools effectively. Wondering if Kotlin is right for your Java team? We explore that very question in another article.

Common Mistake: Don’t try to learn everything at once. Focus on mastering the fundamentals of Kotlin before diving into complex libraries and frameworks. A solid understanding of the basics will make it much easier to learn and use these tools effectively.

Learning Kotlin takes time and effort, but the rewards are well worth it. By following these steps and practicing regularly, you’ll be well on your way to becoming a proficient Kotlin developer. Remember to embrace challenges, experiment with different approaches, and never stop learning. The world of Kotlin is vast and exciting, and there’s always something new to discover. Thinking about the future of mobile development? Check out our take on mobile trends in 2024.

Don’t just read about Kotlin; start coding today. Download IntelliJ IDEA, write your first “Hello, Kotlin!” program, and then commit to spending just 30 minutes each day exploring the language. You’ll be amazed at how quickly you progress and the exciting applications you can build. Your journey to becoming a skilled Kotlin developer starts now. Also, be sure to avoid these common mobile app myths as you begin your development journey!