Kotlin

What is Kotlin?

Kotlin is a general-purpose programming language that is

• cross-platform,
• statically typed
• concise (using type inference)

What is it good for?

• Android native development
  • 2019: Google endorsed as preferred language for Android app development
• Cross-platform mobile development
  • "Write the business logic for your iOS and Android apps with less time and effort – using nothing but Kotlin" Jetbrains
• Cross-platform library development
  • Kotlin/Native uses LLVM to compile Kotlin to static or dynamic native libraries for many platforms.
  • iOS, macOS, Android, Windows, Linux, WebAssembly
• Server-side development
  • Kotlin is JVM compatible so it can be used on top of Java web service frameworks like Spring
• Javascript front-end development
  • Kotlin/JS transpiles to optimally-sized, readable Javascript.
  • Statically-typed interfaces to reference DOM elements and WebGL
  • Server-side interfaces to integrate with Node.js
  • Dukat assists with conversion of TypeScript definitions to Kotlin/JS
  • Writing for React with Kotlin
• Declarative UI for Android apps: Jetpack Compose
  • as of this writing,latest version is 0.1.0-dev16 self-described as evolving with API breaking changes expected

What does it look like?

fun main() {
    println("Hello, world!!!")
    print(factorial(10))
}

fun factorial(i: Int): Int {
    return if (i == 0 || i == 1) { i } else { i * factorial(i-1) }
}

Hello, world!!!
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Some important things to know:

• The Elvis operator
• Smart Casts

Where do I go to learn it?

• Kotlin Playground
• Interactive Exercises: Kotlin Koans
• Kotlin Evolution Proposals KEEP
• Many Android/Kotlin code tutorials and video walkthroughs at raywenderlich.com