Kotlin
in a real-world project

Anton Rutkevich

JunoLab

Who's out there? :)

About me

• Android
• Java, Kotlin, Groovy
• Gradle, mobile CI

Anton Rutkevich

Based on

6 months of production Android app development

Kotlin

• Open source, statically typed JVM language by JetBrains
• Built with "Effective Java" in mind
• Good support / community

History

• Announced in 2011
• Currently 1.0 Beta 2 (Dec 2015)
• 1.0 coming soon
• Bundled with IntelliJ IDEA 15

For Android

• Native support in Android Studio
• Strong Android support
• Java interop is seamless
• Existing Java libraries can be used
• < 1Mb library size; ~ 8.5 K Methods

Shut up and take my money method count

Library	Size	Method count
scala-library-2.11.7	5.7 Mb	50811
groovy-2.4.4	4.6 Mb	28768
kotlin-runtime-1.0.0-beta-2423	231 Kb	1102
kotlin-stdlib-1.0.0-beta-2423	730 Kb	7337

Safety

Compile time safety

Null safety

( Demo 1 )

Easy immutability

( Demo 2 )

Clean code

Higher order functions

( Demo 3 )

Extension functions

( Demo 4 )

Inlined functions

( Demo 5 )

Extension functions
+ RxJava

( Demo 6 )

• Inferred types
• String templates
• Properties
• When (upgraded switch)
• Return if / when / try

• Ranges
• Unchecked exceptions
• Delegates
• Operator overloading
• Type-safe builders
• ...

Tooling

• Compiles a bit slower than Java
• Android Studio is less smart than with Java
• No Lint

Code

• Harder to write hacky tests
• Must be careful when interacting with Java