Kotlin Introduction & JVM Foundations

Why Google made Kotlin the #1 preferred language for Android development

Null Safety & The Billion-Dollar Mistake »Next »

Developed by JetBrains, Kotlin is a modern, statically typed language that compiles to JVM bytecode, JavaScript, and native binaries. In 2019, Google declared Kotlin the premier language for Android.

Why Developers Love Kotlin

100% Java Interoperability: Call existing Java code from Kotlin and vice versa with zero friction.

Concise & Expressive: Eliminates 40% of Java boilerplate (no semicolons, getters/setters, or manual constructors).

val (Immutable) vs var (Mutable): Favoring immutable val variables prevents race conditions and state corruption.

First Kotlin Program (Main.kt)

Try It Yourself »

fun main() {
    // val is read-only (immutable); var is reassignable
    val appName: String = "Codexia Android"
    var activeUsers: Int = 1420
    
    // String templates with $ and ${}
    println("Welcome to $appName! Active learners: $activeUsers")
    
    activeUsers += 1
    println("Updated enrollment: $activeUsers")
}

String templates and concise variable declarations in Kotlin.

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Test Yourself With Exercise

+15 XP

In Kotlin, what is the keyword used to declare a read-only (immutable) variable that cannot be reassigned?

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