Kt

Kotlin

intermediate

Android's language of choice — Java without the boilerplate.

Kotlin is Google's preferred language for Android development and a full modern replacement for Java: null safety built into the type system, concise syntax, coroutines for async work — while running on the JVM and using every Java library ever written. Learn Kotlin and the entire Android ecosystem opens up.

Android AppsBackend (Ktor/Spring)Multiplatform MobileJVM DevelopmentGradle Scripts
0%
0/8 lessons

Setup

For Android, install Android Studio — it bundles everything. To learn the language alone, the Kotlin compiler runs anywhere Java does, or use play.kotlinlang.org with zero install.

Bash
# Fastest: https://play.kotlinlang.org (no install)

# For Android development:
winget install Google.AndroidStudio

# Just the compiler (needs a JDK):
winget install EclipseAdoptium.Temurin.21.JDK
# then via SDKMAN in WSL/Git Bash, or scoop install kotlin

kotlinc hello.kt -include-runtime -d hello.jar
java -jar hello.jar

Lessons

1
Hello, Kotlin
Kotlin's pitch in one file: everything Java does, in half the lines. main doesn'…
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2
Null Safety
The billion-dollar mistake, fixed in the type system. In Kotlin, String and Stri…
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3
Functions, when & Expressions
In Kotlin, if and when produce values. Combined with expression-body functions, …
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4
Classes & Data Classes
A Java class with getters, setters, equals, hashCode, and toString is ~50 lines.…
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5
Collections & Lambdas
filter, map, sumOf, groupBy — Kotlin's collection pipeline turns loop-heavy code…
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6
Coroutines — async Made Simple
Fetch from the network without freezing the UI — the core problem of app develop…
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7
Your First Android Screen
Modern Android UI is Jetpack Compose: describe the screen as Kotlin functions, a…
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8
Kotlin Cheatsheet
Null safety, data classes, collections, and coroutines on one page.
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