A Builder's Intro to Kotlin (Gradle Summit 2017)

Kotlin's popularity has been exploding in the past year. From last year's announcement that Gradle would support it as a build language, to its adoption on large platforms like Android and Spring, to its general applicability for writing IDE and build system plugins, it's hard to find an area that isn't adopting the language in some form.

This talk will be an introduction to the language in the context of Gradle. After covering the language syntax and features and their benefits, we'll look at why it's great for authoring Gradle plugins. Finally, we'll set the stage for Gradle's Kotlin build script support for which there are other full talks at the conference.

Video: https://youtu.be/UAec6OpJiA8

Transcript

1. Jake Wharton
   A Builder's Intro
   to Kotlin
   

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2. Kotlin?
   

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15. Why Kotlin?
    

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16. Plugin Author
    

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17. Plugin Author Buildscript Author
    

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18. Plugin Author Buildscript Author App Developer
    

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19. val firstName: String = "Jake"

    val lastName: String? = null
    

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20. val firstName: String = "Jake"

    val lastName: String? = null
    

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21. val firstName: String = "Jake"

    val lastName: String? = null
    

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22. val firstName: String = "Jake"

    val lastName: String? = null
    

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23. val firstName: String = "Jake"

    val lastName: String? = null
    

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24. val firstName = "Jake"

    val lastName: String? = null
    

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25. class User {

    public String getName() {

    // ...

    }

    public void setName(String name) {

    // ...

    }

    }
    // ^^^ Java
    

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26. class User {

    public String getName() {

    // ...

    }X

    public void setName(String name) {

    // ...

    }Y

    }Z
    // ^^^ Java vvv Kotlin
    val user = User()

    println("Name is " + user.name)
    

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27. class User {

    public String getName() {

    // ...

    }X

    public void setName(String name) {

    // ...

    }Y

    }Z
    // ^^^ Java vvv Kotlin
    val user = User()

    println("Name is " + user.name)X
    

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28. class User {

    public String getName() {

    // ...

    }X

    public void setName(String name) {

    // ...

    }Y

    }Z
    // ^^^ Java vvv Kotlin
    val user = User()

    println("Name is ${user.name}")X
    

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29. class User {

    public String getName() {

    // ...

    }X

    public void setName(String name) {

    // ...

    }Y

    }Z
    // ^^^ Java vvv Kotlin
    val user = User()

    println("Name is $user")X
    

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30. class User {

    public String getName() {

    // ...

    }X

    public void setName(String name) {

    // ...

    }Y

    }Z
    // ^^^ Java vvv Kotlin
    val user = User()

    println("Name is $user")X
    

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31. class User {

    var name = "Jake"

    }
    // ^^^ Kotlin
    

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32. class User {

    var name = "Jake"

    }
    // ^^^ Kotlin vvv Java
    User user = new User();
    System.out.println("Name is " + user.getName());
    

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33. class User {

    var name = "Jake"

    }
    // ^^^ Kotlin vvv Java
    User user = new User();
    System.out.println("Name is " + user.getName());
    

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34. class User {

    var name = "Jake"

    }
    // ^^^ Kotlin vvv Java
    User user = new User();
    System.out.println("Name is " + user.getName());
    user.setName("Jane");
    

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35. class User {

    var name = "Jake"

    }
    // ^^^ Kotlin vvv Java
    User user = new User();
    System.out.println("Name is " + user.getName());
    user.setName("Jane");
    

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36. val user = User()
    

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37. val user = User()

    user = User()
    

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38. val user = User()

    user = User()

    

    var currentUser = User()

    currentUser = User()
    

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39. fun Date.isTuesday(): Boolean {

    return day == 2

    }
    

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40. fun Date.isTuesday(): Boolean {

    return day == 2

    }
    val epoch = Date(1970, 0, 0)

    if (epoch.isTuesday()) {

    println("The epoch was a Tuesday.")

    } else {

    println("The epoch was not a Tuesday.")

    }
    

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41. fun Date.isTuesday(): Boolean {

    return day == 2

    }
    val epoch = Date(1970, 0, 0)

    if (epoch.isTuesday()) {

    println("The epoch was a Tuesday.")

    } else {

    println("The epoch was not a Tuesday.")

    }
    

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42. fun Date.isTuesday(): Boolean {

    return day == 2

    }
    val epoch = Date(1970, 0, 0)

    if (epoch.isTuesday()) {

    println("The epoch was a Tuesday.")

    } else {

    println("The epoch was not a Tuesday.")

    }
    // ^^^ Kotlin vvv Java
    DateKt.isTuesday(date)
    

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43. val executor = Executors.newSingleThreadExecutor();

    executor.execute {Bprintln("Background thread!") }X
    

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44. val executor = Executors.newSingleThreadExecutor();
    val foo = Foo()

    executor.execute(foo::printIt)
    class Foo {
    fun printIt() {B
    println("Background thread!")
    }X
    }
    

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45. val executor = Executors.newSingleThreadExecutor();
    val foo = Foo()

    executor.execute(foo::printIt)
    class Foo {
    fun printIt() {B
    println("Background thread!")
    }X
    }
    

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46. fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }
    

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47. fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }
    

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48. fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }A
    val items = listOf(1, 2, 3)
    val odds = items.filter({ item -> item % 2 != 0 })B
    

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49. fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }A
    val items = listOf(1, 2, 3)
    val odds = items.filter({ item -> item % 2 != 0 })B
    

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50. fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }A
    val items = listOf(1, 2, 3)
    val odds = items.filter({ it % 2 != 0 })B
    

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51. fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }A
    val items = listOf(1, 2, 3)
    val odds = items.filter()B{ it % 2 != 0 }
    

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52. fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }A
    val items = listOf(1, 2, 3)
    val odds = items.filter { it % 2 != 0 }
    

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53. fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }A
    val items = listOf(1, 2, 3)
    val oddList = items.filter { it % 2 != 0 }
    val oddSet = items.filterTo(mutableListOf()) { it % 2 != 0 }
    

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54. fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }A
    val items = listOf(1, 2, 3)
    val odds = items.filter { it % 2 != 0 }
    

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55. inline fun List.filter(predicate: (T) -> Boolean): List {

    // ...

    }A
    val items = listOf(1, 2, 3)
    val odds = items.filter { it % 2 != 0 }
    

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56. inline fun List.filter(predicate: (T) -> Boolean): List {
    val destination = mutableListOf()
    for (item in this) {
    if (predicate(item)) destination.add(item)
    }B
    return destination
    }A
    val items = listOf(1, 2, 3)
    val odds = items.filter { it % 2 != 0 }
    val destination = mutableListOf< >()
    for (item in ) {
    if ( item ) destination.add(item)
    }G
    destination
    

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57. inline fun List.filter(predicate: (T) -> Boolean): List {
    val destination = mutableListOf()
    for (item in this) {
    if (predicate(item)) destination.add(item)
    }B
    return destination
    }A
    val items = listOf(1, 2, 3)
    val destination = mutableListOf()
    for (item in items) {
    if (item % 2 != 0) destination.add(item)
    }G
    val odds = destination
    filter it
    

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58. fun List.filterIsInstance(c: Class): List {

    val destination = mutableListOf()
    for (item in this) {
    if (c.isInstance(item)) destination.add(item)
    }
    return destination

    }A
    

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59. fun List.filterIsInstance(c: Class): List {

    val destination = mutableListOf()
    for (item in this) {
    if (c.isInstance(item)) destination.add(item)
    }G
    return destination

    }A
    

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60. fun List.filterIsInstance(): List {

    val destination = mutableListOf()
    for (item in this) {
    if (item in T) destination.add(item)
    }G
    return destination

    }A
    c: Class

    c.isInstance( )
    

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61. fun List.filterIsInstance(): List {

    val destination = mutableListOf()
    for (item in this) {
    if (item in T) destination.add(item)
    }G
    return destination

    }A
    

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62. inline fun List.filterIsInstance(): List {

    val destination = mutableListOf()
    for (item in this) {
    if (item in T) destination.add(item)
    }G
    return destination

    }A
    

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63. inline fun List.filterIsInstance(): List {

    val destination = mutableListOf()
    for (item in this) {
    if (item in T) destination.add(item)
    }G
    return destination

    }A
    

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64. inline fun List.filterIsInstance(): List {

    val destination = mutableListOf()
    for (item in this) {
    if (item in T) destination.add(item)
    }G
    return destination

    }A
    

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65. inline fun List.filterIsInstance(): List {

    val destination = mutableListOf()
    for (item in this) {
    if (item in T) destination.add(item)
    }
    return destination

    }A
    val list = listOf(1, 2f, 3, 4f)
    val ints = list.filterIsInstance()
    

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66. inline fun List.filterIsInstance(): List {

    val destination = mutableListOf()
    for (item in this) {
    if (item in T) destination.add(item)
    }
    return destination

    }A
    val list = listOf(1, 2f, 3, 4f)
    val ints = list.filterIsInstance()
    ALOAD 7 # item
    INSTANCEOF java/lang/Integer
    IFEQ L8
    ALOAD 5 # destination
    ALOAD 7 # item
    INVOKEINTERFACE java/util/Collection.add (Ljava/lang/Object;)Z
    

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67. class User {D

    val name = "Jake"

    }A
    

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68. class User(name: String) {D

    val name = name

    }A
    

    "Jake"
    

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69. class User(val name: String) {

    }A
    

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70. class User(val name: String)
    

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71. class User(val name: String)
    val jake = User("Jake")
    println("Hello, $jake!")
    

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72. class User(val name: String)
    val jake = User("Jake")
    println("Hello, $jake!")
    Hello, User@3a71f4dd!
    

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73. data class User(val name: String)
    val jake = User("Jake")
    println("Hello, $jake!")
    Hello, User@3a71f4dd!
    

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74. @3a71f4dd
    data class User(val name: String)
    val jake = User("Jake")
    println("Hello, $jake!")
    Hello, User(name=Jake)!
    

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75. data class User(val name: String)
    val jake = User("Jake")
    println("Hello, $jake!")
    Hello, User(name=Jake)!
    

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76. class UserPersisence(db: SqlDatabase) {
    private val deleteByName
    = db.createStatement("DELETE FROM user WHERE name = ?")
    fun delete(name: String) {
    deleteByName.bind(1, name)
    deleteByName.execute()
    }
    }
    

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77. class UserPersisence(db: SqlDatabase) {
    private val deleteByName
    = db.createStatement("DELETE FROM user WHERE name = ?")
    fun delete(name: String) {
    deleteByName.bind(1, name)
    deleteByName.execute()
    }B
    }A
    

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78. class UserPersisence(db: SqlDatabase) {
    private val deleteByName by lazy {
    db.createStatement("DELETE FROM user WHERE name = ?")
    }C
    fun delete(name: String) {
    deleteByName.bind(1, name)
    deleteByName.execute()
    }B
    }A
    

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79. val deleteByName by lazy {
    db.createStatement("DELETE FROM user WHERE name = ?")
    }C
    

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80. val deleteByName by lazy {
    db.createStatement("DELETE FROM user WHERE name = ?")
    }C
    var name by Delegates.observable("Jane") { prop, old, new ->
    println("Name changed from $old to $new")
    }
    

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81. val deleteByName by lazy {
    db.createStatement("DELETE FROM user WHERE name = ?")
    }C
    var name by Delegates.observable("Jane") { prop, old, new ->
    println("Name changed from $old to $new")
    }
    var address by Delegates.notNull()
    

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82. val deleteByName by lazy {
    db.createStatement("DELETE FROM user WHERE name = ?")
    }C
    var name by Delegates.observable("Jane") { prop, old, new ->
    println("Name changed from $old to $new")
    }
    var address by Delegates.notNull()
    val nameView by bindView(R.id.name)
    

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83. val deleteByName by lazy {
    db.createStatement("DELETE FROM user WHERE name = ?")
    }C
    var name by Delegates.observable("Jane") { prop, old, new ->
    println("Name changed from $old to $new")
    }
    var address by Delegates.notNull()
    val nameView by bindView(R.id.name)
    

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84. fun main(vararg args: String) = runBlocking {
    val jobs = List(100_000) {
    launch(CommonPool) {
    delay(1000L)
    print(".")
    }
    }
    jobs.forEach { it.join() }
    }
    

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85. Plugin Author Buildscript Author App Developer
    

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86. Plugin Author Buildscript Author
    App Developer
    

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87. apply plugin: 'org.jetbrains.kotlin.jvm'
    

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88. apply plugin: 'org.jetbrains.kotlin.jvm'
    src/
    main/
    java/
    Fizz.java
    Buzz.java
    

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89. apply plugin: 'org.jetbrains.kotlin.jvm'
    src/
    main/
    java/
    Fizz.java
    Buzz.kt
    

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90. *.java
    *.kt
    

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91. *.java
    *.kt
    kotlinc
    

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92. *.java
    *.kt
    kotlinc
    

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93. *.java
    *.kt
    kotlinc javac
    

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94. *.java
    *.kt
    kotlinc javac
    

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95. *.java
    *.kt
    kotlinc javac
    

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96. kotlin-stdlib
    *.java
    *.kt
    kotlinc javac
    

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97. kotlin-stdlib
    *.java
    *.kt
    kotlinc javac
    

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98. kotlin-stdlib
    *.java
    *.kt
    kotlinc javac
    project(':some-library')
    

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99. apply plugin: 'org.jetbrains.kotlin.jvm'
    

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100. apply plugin: 'org.jetbrains.kotlin.jvm'
     apply plugin: 'org.jetbrains.kotlin.android'
     

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101. apply plugin: 'org.jetbrains.kotlin.jvm'
     apply plugin: 'org.jetbrains.kotlin.android'
     apply plugin: 'kotlin2js'
     

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102. apply plugin: 'org.jetbrains.kotlin.jvm'
     apply plugin: 'org.jetbrains.kotlin.android'
     apply plugin: 'kotlin2js'
     apply plugin: 'konan' # Different classpath dependency
     

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103. apply plugin: 'org.jetbrains.kotlin.jvm'
     apply plugin: 'org.jetbrains.kotlin.android'
     apply plugin: 'kotlin2js'
     apply plugin: 'konan' # Different classpath dependency
     or
     apply plugin: 'org.jetbrains.kotlin.platform.common'
     apply plugin: 'org.jetbrains.kotlin.platform.jvm'
     apply plugin: 'org.jetbrains.kotlin.platform.js'
     apply plugin: 'konan' # Different classpath dependency
     

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104. Plugin Author Buildscript Author App Developer
     

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105. Plugin Author
     Buildscript Author
     App Developer
     

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106. apply plugin: 'org.jetbrains.kotlin.jvm'
     apply plugin: 'org.jetbrains.kotlin.kapt'
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     dependencies {
     compile deps.kotlin.stdLibJre8
     compile deps.javaPoet
     compile deps.autoCommon
     compileOnly deps.autoService
     kapt deps.autoService
     testCompile deps.junit
     testCompile deps.truth
     testCompile deps.compileTesting
     }
     

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107. apply plugin: 'org.jetbrains.kotlin.jvm'
     apply plugin: 'org.jetbrains.kotlin.kapt'
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     dependencies {
     compile deps.kotlin.stdLibJre8
     compile deps.javaPoet
     compile deps.autoCommon
     compileOnly deps.autoService
     kapt deps.autoService
     testCompile deps.junit
     testCompile deps.truth
     testCompile deps.compileTesting
     }
     

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108. apply(plugin: 'org.jetbrains.kotlin.jvm')X
     apply plugin: 'org.jetbrains.kotlin.kapt'
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     dependencies {
     compile deps.kotlin.stdLibJre8
     compile deps.javaPoet
     compile deps.autoCommon
     compileOnly deps.autoService
     kapt deps.autoService
     testCompile deps.junit
     testCompile deps.truth
     testCompile deps.compileTesting
     }
     

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109. apply(singletonMap('plugin', 'org.jetbrains.kotlin.jvm'))X
     apply plugin: 'org.jetbrains.kotlin.kapt'
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     dependencies {
     compile deps.kotlin.stdLibJre8
     compile deps.javaPoet
     compile deps.autoCommon
     compileOnly deps.autoService
     kapt deps.autoService
     testCompile deps.junit
     testCompile deps.truth
     testCompile deps.compileTesting
     }
     

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110. apply(singletonMap('plugin', 'org.jetbrains.kotlin.jvm'))X
     apply plugin: 'org.jetbrains.kotlin.kapt'
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     dependencies {
     compile deps.kotlin.stdLibJre8
     compile deps.javaPoet
     compile deps.autoCommon
     compileOnly deps.autoService
     kapt deps.autoService
     testCompile deps.junit
     testCompile deps.truth
     testCompile deps.compileTesting
     }
     

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111. apply(singletonMap('plugin', 'org.jetbrains.kotlin.jvm'))X
     apply plugin: 'org.jetbrains.kotlin.kapt'
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     dependencies {
     compile deps.kotlin.stdLibJre8
     compile deps.javaPoet
     compile deps.autoCommon
     compileOnly deps.autoService
     kapt deps.autoService
     testCompile deps.junit
     testCompile deps.truth
     testCompile deps.compileTesting
     }
     

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112. apply(singletonMap('plugin', 'org.jetbrains.kotlin.jvm'))X
     apply plugin: 'org.jetbrains.kotlin.kapt'
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     dependencies {
     compile deps.kotlin.stdLibJre8
     compile(deps.javaPoet)
     compile deps.autoCommon
     compileOnly deps.autoService
     kapt deps.autoService
     testCompile deps.junit
     testCompile deps.truth
     testCompile deps.compileTesting
     }
     

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113. apply(singletonMap('plugin', 'org.jetbrains.kotlin.jvm'))X
     apply plugin: 'org.jetbrains.kotlin.kapt'
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     dependencies {
     compile deps.kotlin.stdLibJre8
     compile(deps.javaPoet)
     compile deps.autoCommon
     compileOnly deps.autoService
     kapt deps.autoService
     testCompile deps.junit
     testCompile deps.truth
     testCompile deps.compileTesting
     }
     

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114. android {
     // ...
     testOptions {
     unitTests.all {
     systemProperty('robolectric.dependency.repo.id', 'example-nexus')
     systemProperty('robolectric.dependency.repo.url',
     'https://nexus.example.com/content/groups/public')
     }
     }
     }
     

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115. android {
     // ...
     testOptions {
     unitTests.all {
     systemProperty('robolectric.dependency.repo.id', 'example-nexus')
     systemProperty('robolectric.dependency.repo.url',
     'https://nexus.example.com/content/groups/public')
     }
     }
     }
     

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116. android {
     // ...
     testOptions {
     unitTests.all {
     systemProperty('robolectric.dependency.repo.id', 'example-nexus')
     systemProperty('robolectric.dependency.repo.url',
     'https://nexus.example.com/content/groups/public') }

     

     }
     

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117. apply plugin: 'org.jetbrains.kotlin.jvm'
     apply plugin: 'org.jetbrains.kotlin.kapt'
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     dependencies {
     compile deps.kotlin.stdLibJre8
     compile deps.javaPoet
     compile deps.autoCommon
     compileOnly deps.autoService
     kapt deps.autoService
     testCompile deps.junit
     testCompile deps.truth
     testCompile deps.compileTesting
     }A
     java
     build.gradle
     

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118. apply {
     plugin('org.jetbrains.kotlin.jvm')
     plugin('org.jetbrains.kotlin.kapt')
     }
     java {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     }
     dependencies {
     compile(deps.kotlin.stdLibJre8)
     compile(deps.javaPoet)
     compile(deps.autoCommon)
     compileOnly(deps.autoService)
     kapt(deps.autoService)
     testCompile(deps.junit)
     testCompile(deps.truth)
     testCompile(deps.compileTesting)
     }A
     build.gradle.kts
     

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119. apply {
     plugin('org.jetbrains.kotlin.jvm')
     plugin('org.jetbrains.kotlin.kapt')
     }
     java {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     }
     dependencies {
     compile(deps.kotlin.stdLibJre8)
     compile(deps.javaPoet)
     compile(deps.autoCommon)
     compileOnly(deps.autoService)
     kapt(deps.autoService)
     testCompile(deps.junit)
     testCompile(deps.truth)
     testCompile(deps.compileTesting)
     }A
     build.gradle.kts
     

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120. apply {
     plugin('org.jetbrains.kotlin.jvm')
     plugin('org.jetbrains.kotlin.kapt')
     }
     java {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     }
     dependencies {
     compile(deps.kotlin.stdLibJre8)
     compile(deps.javaPoet)
     compile(deps.autoCommon)
     compileOnly(deps.autoService)
     kapt(deps.autoService)
     testCompile(deps.junit)
     testCompile(deps.truth)
     testCompile(deps.compileTesting)
     }A
     build.gradle.kts
     

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121. apply {
     plugin('org.jetbrains.kotlin.jvm')
     plugin('org.jetbrains.kotlin.kapt')
     }
     java {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     }
     dependencies {
     compile(deps.kotlin.stdLibJre8)
     compile(deps.javaPoet)
     compile(deps.autoCommon)
     compileOnly(deps.autoService)
     kapt(deps.autoService)
     testCompile(deps.junit)
     testCompile(deps.truth)
     testCompile(deps.compileTesting)
     }A
     build.gradle.kts
     

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122. apply {
     plugin('org.jetbrains.kotlin.jvm')
     plugin('org.jetbrains.kotlin.kapt')
     }
     java {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     }
     dependencies {
     compile(deps.kotlin.stdLibJre8)
     compile(deps.javaPoet)
     compile(deps.autoCommon)
     compileOnly(deps.autoService)
     kapt(deps.autoService)
     testCompile(deps.junit)
     testCompile(deps.truth)
     testCompile(deps.compileTesting)
     }A
     build.gradle.kts
     

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123. apply {
     plugin('org.jetbrains.kotlin.jvm')
     plugin('org.jetbrains.kotlin.kapt')
     }
     java {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
     }
     dependencies {
     compile(deps.kotlin.stdLibJre8)
     compile(deps.javaPoet)
     compile(deps.autoCommon)
     compileOnly(deps.autoService)
     kapt(deps.autoService)
     testCompile(deps.junit)
     testCompile(deps.truth)
     testCompile(deps.compileTesting)
     }A
     build.gradle.kts
     

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124. View Slide

125. View Slide

126. Plugin Author Buildscript Author App Developer
     

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127. Plugin Author
     Buildscript Author App Developer
     

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128. class MyPlugin : Plugin {
     override fun apply(project: Project) {
     // ...
     }B
     }A
     

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129. import org.gradle.kotlin.dsl.*
     class MyPlugin : Plugin {
     override fun apply(project: Project) {
     // ...
     }B
     }A
     

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130. kotlin-stdlib
     *.java
     *.kt
     kotlinc javac
     

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131. kotlin-stdlib
     *.java
     *.kt
     kotlinc javac
     apply plugin: 'your-gradle-plugin'
     

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132. View Slide

133. View Slide

134. +
     

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135. jakewharton
     jakewharton
     jakewharton
     twitter.com/
     github.com/
     .com
     A Builder's Intro
     to Kotlin
     

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