Kotlin

Kotlin is a statically typed, modern programming language developed by JetBrains and adopted by Google in 2017 as the preferred language for Android development. Kotlin runs on the JVM (with full Java interop), compiles to JavaScript and native code, and powers both server and mobile codebases.

Key language features

• Null safety. Nullable and non-nullable types are distinct; the compiler enforces null checks.
• Concise syntax. Data classes, lambdas, type inference, smart casts, extension functions.
• Coroutines. Built-in cooperative concurrency for async work and structured concurrency.
• Java interop. Drop-in replacement for Java; mixed Kotlin+Java codebases are common.
• Multiplatform. Kotlin Multiplatform shares code across JVM, JS, native, Android, and iOS.

Where Kotlin is used

• Android apps via Jetpack Compose or the View system
• Server-side (Ktor, Spring Boot with Kotlin)
• Kotlin Multiplatform Mobile (KMM) for iOS+Android shared code
• CLI tools, build scripts (Gradle Kotlin DSL)