Kotlin – Get Started: Hello World & Your First Kotlin Program

Introduction – Starting Your Kotlin Journey

Ready to write your first lines of Kotlin? Whether you’re a beginner or transitioning from Java, starting with a simple Kotlin program like “Hello World” is the best way to understand the syntax, compiler behavior, and IDE workflow. Kotlin’s clear and concise structure makes it beginner-friendly and highly productive.

In this guide, you’ll learn:

• How to write and run your first Kotlin program
• The structure of a basic Kotlin file
• Differences between using Kotlin in CLI, IDEs, or online editors
• How the Kotlin main() function works

Your First Kotlin Program – “Hello, World!”

Let’s begin with the classic starting point in every language: printing “Hello, World!” to the console.

Kotlin Hello World Example

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

Code Breakdown:

Output:

Hello, World!

How to Run Your First Kotlin Program

Option 1: Using IntelliJ IDEA

1. Open IntelliJ ➝ File ➝ New Project ➝ Kotlin ➝ Kotlin/JVM.
2. Create a file: Main.kt
3. Paste the Hello World code.
4. Click Run or right-click → Run ‘MainKt’

Option 2: Using Command Line (CLI)

1. Install Kotlin compiler CLI via SDKMAN or package manager.
2. Save code as hello.kt

kotlinc hello.kt -include-runtime -d hello.jar
java -jar hello.jar

You should see: Hello, World!

Option 3: Using Kotlin Playground (Online)

1. Visit https://play.kotlinlang.org
2. Paste the code and click Run

Instant output in your browser without setup.

Writing a Slightly Advanced Program

Let’s modify the program to accept input and greet the user.

fun main() {
    print("Enter your name: ")
    val name = readLine()
    println("Hello, $name! Welcome to Kotlin.")
}

Code Explanation:

• print() – Prints without newline.
• readLine() – Reads user input from the console.
• $name – String template to embed variable inside text.

Sample Output:

Enter your name: Arjun
Hello, Arjun! Welcome to Kotlin.

Structure of a Kotlin File

Best Practices for Getting Started

Summary – Recap & Next Steps

You’ve just written your first Kotlin program and learned the structure of a basic Kotlin app. With just a few lines of code, Kotlin shows off its simplicity, readability, and developer-friendliness.

Key Takeaways:

• The main() function is the entry point for Kotlin applications.
• Use println() for output and readLine() for input.
• You can run Kotlin using IDEs, CLI, or online playgrounds.

Practical Use:
From printing messages to taking input, Kotlin makes it easy to start writing programs—ideal for Android apps, backend systems, or scripting tasks.

FAQs – Kotlin First Program

What is the main function in Kotlin?
The main() function is the entry point for every Kotlin program. It’s where execution begins.

Do I need a class to run Kotlin code?
No. Unlike Java, Kotlin doesn’t require wrapping your code inside a class for a basic program.

How do I run Kotlin code in a browser?
Use Kotlin Playground to write and execute code instantly online.

Can Kotlin be run without IntelliJ?
Yes. You can compile and run Kotlin from the command line using the kotlinc compiler and Java runtime.

What’s the difference between print() and println() in Kotlin?
print() doesn’t add a newline at the end, while println() adds a newline after printing the output.