Technology

Kotlin

Modern language from JetBrains; Google’s preferred language for Android. Interoperable with Java, more concise and safer.

Kotlin has replaced Java as the preferred language for Android. Since Google recommended Kotlin in 2019, adoption has grown fast. Kotlin offers a more modern, concise syntax, null-safe types and full interoperability with existing Java. It also powers backend (Ktor), multiplatform (KMP) and UI (Compose).

What is Kotlin?

Kotlin is a statically typed language developed by JetBrains, first released in 2016. It compiles to JVM bytecode (runs wherever Java runs), to JavaScript (Kotlin/JS) and to native (Kotlin/Native). It is fully interoperable with Java: Kotlin can use Java libraries and vice versa. Kotlin Multiplatform (KMP) shares business logic between Android, iOS, Web and Desktop. Jetpack Compose – the modern declarative UI toolkit for Android – is written in Kotlin.

How does Kotlin work?

Kotlin is compiled to JVM bytecode by the Kotlin compiler; on Android it is compiled with the Android Gradle Plugin to DEX. Features like null safety (types are non-nullable by default), extension functions, data classes, coroutines (lightweight concurrency) and sealed classes make code shorter and safer than equivalent Java. Kotlin Multiplatform uses expect/actual for platform-specific code.

Practical Examples

Android app with Jetpack Compose: Declarative UI in Kotlin – less code, better performance and testing than the old View system.

Backend with Ktor: Kotlin web framework for REST APIs with coroutines and native Kotlin syntax.

Kotlin Multiplatform: Shared network and business logic for Android and iOS – only UI is platform-specific.

Spring Boot + Kotlin: Enterprise backend combining Spring’s robustness with Kotlin’s clarity.

Typical Use Cases

Android: New apps and migrating Java apps to Kotlin

Backend: Servers with Ktor, Spring Boot or Micronaut in Kotlin

Multiplatform: Shared code for Android and iOS with KMP

Data science: Kotlin notebooks (Jupyter) for analysis and viz

Scripting: Build scripts (Gradle Kotlin DSL) and automation

Advantages and Disadvantages

Advantages

Null safety: NullPointerExceptions caught at compile time
Concise: Often 30–40% less code than Java (data classes, extensions)
Java interop: Existing Java codebases can adopt Kotlin gradually
Coroutines: Clean async code without callback hell
Google backing: Preferred for Android with strong IDE support

Disadvantages

Compile time: Kotlin compiles a bit slower than Java (improving)
Smaller community: Fewer answers and libraries than Java
Learning: Advanced features (coroutines, sealed classes, DSLs) take time
KMP on iOS: Kotlin Multiplatform for iOS is less mature than Flutter/React Native

Frequently Asked Questions about Kotlin

Should I learn Kotlin or Java for Android?

Kotlin. Google recommends it for Android. New Android APIs and Jetpack libraries are Kotlin-first. Jetpack Compose is Kotlin-only. Java is still useful for legacy codebases, but for new projects there’s no reason to choose Java over Kotlin.

Can I migrate existing Java code to Kotlin?

Yes, gradually. Kotlin and Java can coexist. IntelliJ has a Java-to-Kotlin converter (starting point only; manual cleanup needed). Prefer writing new code in Kotlin and migrating Java when you touch it. Full rewrites are rarely necessary.

Kotlin or Flutter for Android?

Native Kotlin + Compose when: you need max performance, full Android APIs, Android only, and Kotlin expertise. Flutter when: you want one codebase for iOS and Android and cost matters. KMP is a middle path: shared logic in Kotlin, native UIs per platform.

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