Kotlin > 🏝 (Kotlin: more than an island)

2017-07-15: MobileOptimized 2017
2017-05-31: https://www.meetup.com/GDG-Berlin-Android/events/238173227

The last Google I/O was probably the most exciting ever, especially for one reason: Kotlin received official recognition as a first-class citizen on Android.
The quantity of developers cheering for this shouldn't come as a surprise, as some of them have already been using the language for years, and for good reasons.
Join us to understand what Kotlin really is, and witness how its principles and advanced features make it so unique today, plus what will make it transcend into something even more powerful in the future.

Animated slides (Keynote): https://goo.gl/QfQLdp

Transcript

1. !
   

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2. !
   “…Kotlin is a new JVM language…”
   

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3. !
   “…Kotlin is a new JVM language…”
   

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4. !
   “…Kotlin is a new JVM language…”
   

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7. made by JetBrains
   open source, non-profit foundation
   pragmatic
   safe(r than Java)
   “good” magic ✨
   FUN
   

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8. packages
   optional
   no need to match folder
   files
   multiple classes
   top level functions
   

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9. // src/main/kotlin/covfefe/Whatever.kt
   fun main(args: Array) {
   }
   println("Hello World!")
   

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10. fun main(args: Array) {
    val immutable = 0
    immutable += 1
    }
    

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11. fun main(args: Array) {
    var mutable = 0
    mutable += 1
    }
    

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12. fun main(args: Array) {
    val nullable: String? = null
    val alternative = nullable ?: "¯\_(ϑ)_/¯"
    val lengthOrNull = nullable?.length
    if (nullable != null) {
    println(nullable.length)
    }
    }
    }
    

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13. fun Int.twice() = this * 2
    fun test() = 1.twice() // 2
    

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14. inline fun Map.getOrElse(
    key: K,
    defaultValue: () -> V
    ) =
    get(key) ?: defaultValue()
    

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15. abstract class NetworkResult {
    object Cancelled : NetworkResult()
    data class Success(val json: String) : NetworkResult()
    data class Error(val error: Throwable) : NetworkResult()
    }
    fun test(result : NetworkResult) = when (result) {
    NetworkResult.Cancelled -> null
    is NetworkResult.Success -> result.json
    is NetworkResult.Error -> throw result.error
    else -> error("WTF")
    }
    

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16. sealed
    object Cancelled : NetworkResult()
    data class Success(val json: String) : NetworkResult()
    data class Error(val error: Throwable) : NetworkResult()
    }
    fun test(result : NetworkResult) = when (result) {
    NetworkResult.Cancelled -> null
    is NetworkResult.Success -> result.json
    is NetworkResult.Error -> throw result.error
    class NetworkResult {
    }
    

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17. why?
    

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18. everything you can do in Kotlin can be done in Java
    

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19. everything you can do in Java can be done in bytecode
    

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20. high level abstractions, enforced by the compiler
    extend the language through DSL
    built in symbiosis with tools
    moving fast, but carefully
    change of mindset
    

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21. myths
    

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22. slow compilation
    runtime overhead
    learning curve
    not knowing what’s really going on
    confusing without IDE
    

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23. cons
    

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24. occasional rough edges around tooling
    not being able to go back to Java, ever
    

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25. future
    

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26. immutable collections
    universal serialization
    type classes
    multiplatform
    metaprogramming
    

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27. Official website
    goo.gl/xL99fk
    Kotlin and Android (blog)
    goo.gl/FQYAcW
    Introduction to Kotlin (video)
    goo.gl/3n6wic
    Life is Great and Everything Will Be Ok, Kotlin is Here (video)
    goo.gl/NTaYqi
    Using Project Kotlin for Android (doc)
    goo.gl/T0SDTJ
    The Future of Kotlin (video)
    goo.gl/INLPDl
    Kotlin 1.1 (video)
    goo.gl/iKojmn
    

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28. BIT
    .LY
    /KO
    TLIN
    -M
    O
    RE
    -TH
    A
    N
    -A
    N
    -ISLA
    N
    D
    Eugenio
    Marletti
    @workingkills
    

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