2017_12_18-19_Kotlin_Conf_Report_Kotlin_Types_Updated

CA.kt #5, 6 Kotlin Conf Report in Osaka, Fukuoka
Kotlin Types
This presentation based on Kotlin Exposed Type by Svetlana Isakova in Kotlin Conf 2017.

https://cyberagent.connpass.com/event/73540/
https://cyberagent.connpass.com/event/73541/

Transcript

1. Kotlin Conf報告会
   @ CA.kt #5, 6
   AAkira
   - Kotlin Types -
   

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2. @_a_akira
   AAkira
   CyberAgent, Inc.
   Akira Aratani
   private lateinit var aakira : User
   data class User(val name: String, val twitterId: String, val githubId: String, val company: String)
   print("Name : ${aakira.name}”)
   println("Github Id : ${aakira.githubId}")
   print("Twitter Id : ${aakira.twitterId}")
   println("Company : ${aakira.company}")
   $ whois
   

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3. About
   • 生放送配信プラットフォーム　≠ AbemaTV　≒
   • M11の頃からFull Kotlinで開発
   • サーバサイドも1年前からKotlinを使用
   

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4. 私とKotlin
   M1 2012-04-12
   M11 2015-03-19
   M14 2015-10-01
   1.0-beta4 2015-12-22
   M13 2015-09-16
   1.0 2016-02-16
   1.0-RC 2016-02-04
   2016-01-21 Release
   2015-04 開発開始
   kotlin
   FRESH
   1.1 2017-03-01
   2017-05-15 Renewal
   

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7. Svetlana Isakova
   @JetBrains
   Kotlin in Action の著者の1人
   

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9. Agenda
   • Basic types
   • Nullable types
   • Collection types
   

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10. Agenda
    • Basic types
    • Nullable types
    • Collection types
    • Kotlin/Java types
    • Any, Unit, Nothing, void
    • Collections
    →
    

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11. Kotlin types
    Java types
    

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12. Kotlin, Java Types
    fun foo(): Int = 1
    fun bar(): Int? = 1
    

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13. Kotlin, Java Types
    

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14. Kotlin, Java Types
    public static final int foo() {
    return 1;
    }
    @Nullable
    public static final Integer bar() {
    return Integer.valueOf(1);
    }
    

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15. Kotlin, Java Types
    public static final int foo() {
    return 1;
    }
    @Nullable
    public static final Integer bar() {
    return Integer.valueOf(1);
    }
    

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16. Kotlin, Java Types
    Int → int
    Int? → java.lang.Integer
    

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17. Kotlin, Java Types
    Double → double
    Double? → java.lang.Double
    Boolean → boolean
    Boolean? → java.lang.Boolean
    

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18. Kotlin, Java Types
    List → java.util.List
    kotlin.String → java.lang.String
    Array → Integer[]
    

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19. Kotlin, Java Types
    List → java.util.List
    kotlin.String → java.lang.String
    Array → Integer[]
    

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20. Kotlin, Java Types
    "one.two.".replaceAll(".", "*")
    

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21. Kotlin, Java Types
    "one.two.".replaceAll(".", "*")
    ********
    

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22. Kotlin, Java Types
    "one.two.".replaceAll(".", "*")
    "one.two.".replace(".", "*")
    ********
    

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23. Kotlin, Java Types
    "one.two.".replaceAll(".", "*")
    "one.two.".replace(".", "*")
    ********
    one*two*
    

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24. Kotlin, Java Types
    "one.two.".replace(".".toRegex(), "*")
    "one.two.".replaceAll(".", "*")
    "one.two.".replace(".", "*")
    ********
    one*two*
    

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25. Any, Unit, Nothing, void
    

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26. Any java.lang.Object
    Any, Unit, Nothing, void
    

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27. Any, Unit, Nothing, void
    The root of the Kotlin class hierarchy.
    Every Kotlin class has [Any] as a superclass.
    Any
    

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28. Any, Unit, Nothing, void
    log(2017)
    fun log(any: Any) {
    println("Value: $any")
    }
    fun log(i: Int) {
    println("Value: $i”)
    }
    

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29. Any, Unit, Nothing, void
    log(2017)
    fun log(any: Any) {
    println("Value: $any")
    }
    fun log(i: Int) {
    println("Value: $i”)
    }
    Auto boxing
    

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30. Any, Unit, Nothing, void
    fun log(i: Int) {
    println("Value: $i”)
    }
    

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31. Any, Unit, Nothing, void
    fun log(any: Any) {
    println("Value: $any")
    }
    

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32. Any, Unit, Nothing, void
    Int String
    Any
    

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33. val hoge: Int? = 2017
    log(hoge)
    fun log(any: Any) {
    println("Value: $any")
    }
    Any, Unit, Nothing, void
    

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34. val hoge: Int? = 2017
    log(hoge)
    fun log(any: Any) {
    println("Value: $any")
    }
    Any, Unit, Nothing, void
    ⇨ Compile Error
    

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35. Any, Unit, Nothing, void
    Any Nullable Type
    Any?
    Non-null Type
    

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36. Any, Unit, Nothing, void
    void
    Unit
    Nothing
    

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37. Any, Unit, Nothing, void
    void
    Unit
    Nothing ≠ ,
    

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38. Any, Unit, Nothing, void
    void
    Unit
    

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39. Any, Unit, Nothing, void
    Unit
    The type with only one value: the Unit object.
    This type corresponds to the `void` type in Java.
    

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40. Any, Unit, Nothing, void
    void
    Unit
    ⇨ 意味のない値を返す
    =
    

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41. Any, Unit, Nothing, void
    Nothing has no instances.
    You can use Nothing to represent "a value that never exists”:
    for example, if a function has the return type of Nothing,

    it means that it never returns (always throws an exception).
    Nothing
    

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42. Any, Unit, Nothing, void
    Nothing
    ⇨ 存在しないを表す, 値は返さない
    

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43. Any, Unit, Nothing, void
    val foo = if (bar) {
    123
    } else {
    fail()
    }
    fun fail() {
    throw IllegalStateException()
    }
    

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44. Any, Unit, Nothing, void
    val foo = if (bar) {
    123
    } else {
    fail()
    }
    fun fail(): Unit {
    throw IllegalStateException()
    }
    

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45. Any, Unit, Nothing, void
    val foo = if (bar) {
    123
    } else {
    fail()
    }
    fun fail(): Unit {
    throw IllegalStateException()
    }
    

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46. Any, Unit, Nothing, void
    val foo = if (bar) {
    123
    } else {
    fail()
    }
    fun fail(): Unit {
    throw IllegalStateException()
    }
    Int
    Unit
    

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47. Any, Unit, Nothing, void
    Int Unit
    Any
    

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48. Any, Unit, Nothing, void
    val foo: Any = if (bar) {
    123
    } else {
    fail()
    }
    fun fail(): Unit {
    throw IllegalStateException()
    }
    

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49. Any, Unit, Nothing, void
    val foo: Any = if (bar) {
    123
    } else {
    fail()
    }
    fun fail(): Unit {
    throw IllegalStateException()
    }
    ⇨ fooはInt型にしたい
    

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50. Any, Unit, Nothing, void
    val foo = if (bar) {
    123
    } else {
    fail()
    }
    fun fail(): Nothing {
    throw IllegalStateException()
    }
    

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51. Any, Unit, Nothing, void
    val foo = if (bar) {
    123
    } else {
    fail()
    }
    fun fail(): Nothing {
    throw IllegalStateException()
    }
    Int
    Nothing
    

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52. Any, Unit, Nothing, void
    Int Unit
    Any
    Nothing
    

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53. Any, Unit, Nothing, void
    val foo: Int = if (bar) {
    123
    } else {
    fail()
    }
    fun fail(): Nothing {
    throw IllegalStateException()
    }
    

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54. Any, Unit, Nothing, void
    val foo: Int = if (bar) {
    123
    } else {
    fail()
    }
    fun fail(): Nothing {
    throw IllegalStateException()
    }
    

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55. Nothing?
    Any, Unit, Nothing, void
    

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56. Any, Unit, Nothing, void
    Int Unit
    Any
    Nothing
    

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57. Any, Unit, Nothing, void
    Non-null Type
    Any
    Nothing
    Non-null Type
    

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58. Any, Unit, Nothing, void
    Any
    Any?
    Non-null Type
    Nothing
    

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59. Any, Unit, Nothing, void
    Any Nullable Type
    Any?
    Non-null Type
    Nothing
    

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60. Any, Unit, Nothing, void
    Any Nullable Type
    Any?
    Non-null Type Nothing?
    Nothing
    

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61. Collections
    

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62. Collections
    kotlin.MutableList
    kotlin.List
    

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63. Collections
    val mutableList = mutableListOf(1, 2, 3)
    val list: List = mutableList
    println(list) // [1, 2, 3]
    

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64. Collections
    val mutableList = mutableListOf(1, 2, 3)
    val list: List = mutableList
    println(list) // [1, 2, 3]
    mutableList.add(4)
    println(list)
    

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65. Collections
    val mutableList = mutableListOf(1, 2, 3)
    val list: List = mutableList
    println(list) // [1, 2, 3]
    mutableList.add(4)
    println(list) // [1, 2, 3, 4]
    

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66. Collections
    ⇨ Read-only ≠ immutable
    mutableList.add(4)
    println(list) // [1, 2, 3, 4]
    

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67. Collections
    fun foo(): List = listOf(1)
    fun bar(): MutableList = mutableListOf(1)
    ⇨ Decompile
    

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68. Collections
    @NotNull
    public static final List foo() {
    return CollectionsKt.listOf(Integer.valueOf(1));
    }
    @NotNull
    public static final List bar() {
    return CollectionsKt.mutableListOf(

    new Integer[]{Integer.valueOf(1)});
    }
    

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69. Collections
    @NotNull
    public static final List foo() {
    return CollectionsKt.listOf(Integer.valueOf(1));
    }
    @NotNull
    public static final List bar() {
    return CollectionsKt.mutableListOf(

    new Integer[]{Integer.valueOf(1)});
    }
    

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70. Collections
    kotlin.MutableList
    kotlin.List
    java.util.ArrayList
    

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71. Summary
    

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72. Summary
    • Decompile to Java code
    • Nothing ≠ Unit, void
    • Read-only ≠ immutable
    

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73. Have a nice Kotlin!
    

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