Getting Started with Kotlin

Kotlin is a modern, statically typed programming language designed to boost developer productivity while maintaining simplicity and readability. Developed by JetBrains, Kotlin has rapidly become a preferred choice for building applications across different domains, from Android mobile apps to backend systems and even cross-platform solutions. Its concise syntax reduces boilerplate code, making programs easier to write, maintain, and understand.

One of the key reasons for Kotlin's popularity is its seamless interoperability with Java, allowing developers to adopt it gradually without discarding existing projects. Android development, in particular, has seen widespread adoption of Kotlin, as Google officially supports it as the recommended language for building Android apps. Beyond mobile, Kotlin is widely used in server-side development with frameworks like Ktor and Spring, as well as in multiplatform projects that share code across Android, iOS, and web applications.

Kotlin's design emphasizes safety, expressiveness, and modern features such as null-safety, coroutines for concurrency, and extension functions.

Setting Up Kotlin

Before diving into Kotlin syntax and building your first applications, you need to set up a proper development environment. Fortunately, Kotlin offers flexibility: you can work with it in IntelliJ IDEA, Android Studio, or directly from the command line interface (CLI). Each method suits different types of developers. Beginners often prefer an IDE like IntelliJ IDEA or Android Studio, while more experienced developers may choose CLI for quick experiments, scripting, or server-side development.

This chapter provides a step-by-step guide for installing Kotlin on your system, verifying the setup, and writing your very first Kotlin program. By the end of this chapter, you'll be ready to start coding confidently in Kotlin.

1. Choosing Your Development Environment

Kotlin is designed to be versatile and platform-independent. You can use it for Android development, backend applications, or even scripting tasks. Depending on your goals, you should select an environment that suits your workflow:

? IntelliJ IDEA: Best suited for general Kotlin development, desktop apps, and backend projects. ? Android Studio: The go-to choice for Android development using Kotlin. ? Kotlin CLI (Command Line): Great for quick experimentation, scripting, and developers who prefer working outside an IDE.

In most cases, you'll end up using more than one of these environments, so it's worth understanding how to set up all three.

2. Setting Up Kotlin in IntelliJ IDEA

Step 1: Download and Install IntelliJ IDEA

1. Visit JetBrains IntelliJ IDEA.
2. Download either:

 Community Edition (free and open source) - ideal for Kotlin learners.  Ultimate Edition (paid) - provides advanced features, mainly useful for enterprise development.

1. Install IntelliJ IDEA following your operating system's standard installation process:

 On Windows, run the installer .exe.  On macOS, open the .dmg file and drag IntelliJ into your Applications folder.  On Linux, unpack the .tar.gz file and run the idea.sh script.

Step 2: Create a New Kotlin Project

1. Open IntelliJ IDEA.
2. On the welcome screen, select New Project.
3. Choose Kotlin JVM | IDEA.
   (If you're building for Android, you'd instead use Android Studio-covered later in this chapter.)
4. Name your project (e.g., HelloKotlin).
5. Choose a location for the project and click Finish.

Step 3: Write Your First Kotlin Program

Once the project is created:

1. Right-click the src folder.
2. Select New Kotlin File/Class.
3. Name the file Main.
4. Add the following code:

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

Step 4: Run the Program

? Click the green triangle (Run button) on the left of the main function. ? You should see the output in the console:

Hello, Kotlin from IntelliJ IDEA!

At this point, your IntelliJ setup is complete.

3. Setting Up Kotlin in Android Studio

Android Studio is based on IntelliJ IDEA but comes pre-packaged with Android-specific tools. Since Google officially supports Kotlin for Android development, Android Studio provides excellent Kotlin integration out of the box.

Step 1: Download and Install Android Studio

1. Visit Android Studio.
2. Download the installer for your platform (Windows, macOS, Linux).
3. Install Android Studio:

 On Windows, run the .exe installer.  On macOS, drag the app into Applications.  On Linux, extract the archive and run studio.sh.

Step 2: Create a New Kotlin Android Project

1. Launch Android Studio.
2. Click New Project.
3. Choose a template (e.g., Empty Activity).
4. Make sure the Language is set to Kotlin.
5. Set the project name and package name.
6. Click Finish.

Step 3: Verify Kotlin is Enabled

? Open MainActivity.kt in the app/src/main/java directory. ? You should see Kotlin code already in place, something like:

package com.example.myfirstkotlinapp

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle

class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
}

Step 4: Run the Android App

? Connect a physical Android device (with USB debugging enabled) or start an Android Emulator. ? Click Run (green triangle). ? Your app should build and launch, confirming Kotlin is successfully configured.

4. Setting Up Kotlin via the Command Line (CLI)

Sometimes you don't want a full IDE. For quick experiments or lightweight development, you can install the Kotlin compiler and use the CLI.

Step 1: Install the JDK

Kotlin runs on the Java Virtual Machine (JVM). You'll need Java installed:

1. Download OpenJDK from Adoptium or Oracle JDK.
2. Install it according to your OS instructions.
3. Verify installation:

java -version

You should see something like:

openjdk version "17.0.2" 2023-01-17

Step 2: Install the Kotlin Compiler

1. Visit the official Kotlin website: Kotlin Releases.
2. Download the compiler distribution (kotlin-compiler-*.zip).
3. Extract the archive to a location on your computer.
4. Add the bin directory to your system PATH.

For example:

? On Linux/macOS:

export PATH=$PATH:/path/to/kotlinc/bin

? On Windows:
Add C:\path\to\kotlinc\bin to your Environment Variables.

Step 3: Verify...