1. An Introduction
to Kotlin JVM language
Andrius Klimavičius

2. Intro
• JVM language
• Android and browser support.
• Developed by JetBrains
• Open Source
• First appeared in 2011
• Still in Beta (v1.0.0-beta-3595)

3. Kotlin
google: kotlin logo

4. Modern Language for
Industry
• 100% interoperable with Java
• Concise - no boilerplate code
• Safe - convert runtime errors into compile time
• Tools support (command-line, plugins)
• Targets Java 6

5. Comparison
• Runtime error -> Compile time errors

6. Kotlin addresses Java
problems
• Null references are controlled by the type system.
• No raw types
• Arrays in Kotlin are invariant
• Kotlin has proper function types, as opposed to Java’s
SAM-conversions
• Kotlin does not have checked exceptions
• Use-site variance without wildcards (<? extends T>)

7. Kotlin vs Java
• No checked exceptions
• No primitive types that are not classes
• No static members
• No non-private fields
• No wildcard-types

8. Kotlin vs Java (2)
• Function literals + Inline
functions
• Extension functions
• Null-safety
• Smart casts
• String templates
• Properties
• First-class delegation
• Type inference
• Singletons
• Range expressions
• Operator overloading
• Companion objects

9. Features
• String templates
• Named arguments & defaults (verbose code)
• Lambda expressions
• Null-Safety (nullable, non-nullable refs)
• Functional programming methods (filter,map,…)
• Extensions (like Objective-C, C#)
• Auto generated POJOs (data class)

10. Features (2)
• Destructuring Declarations
• Generics (Java)
• Ranges
• Operator Overloading
• Optional semi-colons
• Android support
• ….

11. Hello World!

12. Variables

13. String templates

14. String templates

15. Functions

16. Named params & defaults

17. Lambda expressions

18. Null-safety

19. Basic FP methods like
filtering

20. Extensions

21. Data classes

22. Smart Casts

23. Call Java from Kotlin
println("Code in Kotlin")

24. Call Kotlin from Java

25. Reference
• https://kotlinlang.org
• https://prezi.com/5krzwy15ixea/kotlin-on-
android-mobiconf-2015/