1. Kotlin makes Java
Null and Void
@chetbox

2. Who is this guy?

9. Firebase
+

11. You can use Kotlin in production
today

12. fun main(args: Array<String>) {
println("Hello, world!")
}

13. Optional types

14. var name: String? = …
val name: String = …

15. println(name!!)
println(name.length)

16. @NonNull
@Nullable

18. Classes

19. class Foo { }

20. class MyModel(
foo: Int,
val bar: Int,
private var baz: Int
)

21. data class LatLng(
val lat: Double,
val lng: Double
)

22. Java interop

23. class Foo {
companion object {
fun bar() { … }
}
}

24. // From Kotlin
Foo.bar()

25. // From Java
Foo.Companion.bar()

26. Functional programming

27. listOf(1 to "one", 2 to "2", null)
.filterNotNull()
.map { (a, b) -> "$a" == b }

28. inline fun log(f: () -> String) {
println(“${time()}: ${f()}“)
)
log(readMsg)
log { “Got value: ${readMsg()}” }

29. Extension functions

30. fun List<Location>.totalDistance() =
zipWithNext()
.fold(0f) {
total, (current, next) ->
total + current.distanceTo(next)
}

31. How do I convert my
Java project to Kotlin?

32. IntelliJ is your Sensei
Converting “var” to “val”
“when” clauses
Optional types
Idiomatic Kotlin

33. It looks like you’re
pasting Java code.
Shall I convert it to
Kotlin for you?

34. Kotlin > Java
Shorter code ✂
Null safety
Easy Java interop ↔
First-class IDE support from IntelliJ
Lot of libraries are now being written in Kotlin
Official Android examples in Java and Kotlin

35. Kotlin vs. Swift

36. func double(
_ numbers: [Int]
) -> [Int] {
return numbers.map { 2 * $0 }
}
let numbers: [Int] = 1 ... 10
print(double(numbers))

37. fun double(
numbers: List<Int>
) : List<Int> {
return numbers.map { 2 * it }
}
val numbers = 1 .. 10
println(double(numbers))

38. fun double(
numbers: List<Number>
) = numbers.map { 2 * it }
val numbers = 1 .. 10
println(double(numbers))

39. val numbers = 1..10
println(numbers.map { 2 * it })

40. Learn more
Talk: Kotlin in Production
Talk: Life is Great and Everything Will Be Ok, Kotlin is Here
Swift is like Kotlin
Christina Lee - Pinterest
Jake Wharton - Google
Kotlinlang Slack
Fragmented podcast
Talking Kotlin podcast

41. Questions?
Or find me on Twitter: @chetbox