Kotlin's Advanced Language Features

Transcript

1. Kotlin’s
   Advanced Language Features
   

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2. High Order Function's Extension
   

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3. fun String.blowUp() {
   boom()
   }
   "Nooooo".blowUp()
   

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4. fun buildString(
   builderAction: (StringBuilder) -> Unit
   ): String {a
   }b
   fun main(args: Array) {c
   }e
   

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5. fun buildString(
   builderAction: (StringBuilder) -> Unit
   ): String {a
   val sb = StringBuilder()
   builderAction(sb)
   return sb.toString()
   }b
   fun main(args: Array) {c
   }e
   

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6. fun buildString(
   builderAction: (StringBuilder) -> Unit
   ): String {a
   val sb = StringBuilder()
   builderAction(sb)
   return sb.toString()
   }b
   fun main(args: Array) {c
   val s = buildString({ stringBuilder ->
   stringBuilder.append("Hello, ")
   stringBuilder.append("World!")
   })d
   }e
   

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7. fun buildString(
   builderAction: (StringBuilder) -> Unit
   ): String {a
   val sb = StringBuilder()
   builderAction(sb)
   return sb.toString()
   }b
   fun main(args: Array) {c
   val s = buildString { stringBuilder ->
   stringBuilder.append("Hello, ")
   stringBuilder.append("World!")
   }d
   }e
   

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8. fun buildString(
   builderAction: (StringBuilder) -> Unit
   ): String {a
   val sb = StringBuilder()
   builderAction(sb)
   return sb.toString()
   }b
   fun main(args: Array) {c
   val s = buildString {
   it.append("Hello, ")
   it.append("World!")
   }d
   }e
   

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9. fun buildString(
   builderAction: (StringBuilder) -> Unit
   ): String {a
   val sb = StringBuilder()
   builderAction(sb)
   return sb.toString()
   }b
   fun main(args: Array) {c
   val s = buildString {
   append("Hello, ")
   append("World!")
   }d
   }e
   

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10. fun buildString(
    builderAction: StringBuilder.() -> Unit
    ): String {a
    val sb = StringBuilder()
    builderAction(sb)
    return sb.toString()
    }b
    fun main(args: Array) {c
    val s = buildString {
    append("Hello, ")
    append("World!")
    }d
    }e
    

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11. fun buildString(
    builderAction: StringBuilder.() -> Unit
    ): String {a
    val sb = StringBuilder()
    sb.builderAction()
    return sb.toString()
    }b
    fun main(args: Array) {c
    val s = buildString {
    append("Hello, ")
    append("World!")
    }d
    }e
    

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12. fun buildString(
    builderAction: StringBuilder.() -> Unit
    ): String {a
    val sb = StringBuilder()
    sb.builderAction()
    return sb.toString()
    }b
    fun main(args: Array) {c
    val s = buildString {
    append("Hello, ")
    append("World!")
    }d
    }e
    

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13. fun buildString(
    builderAction: StringBuilder.() -> Unit
    ): String {a
    val sb = StringBuilder()
    sb.builderAction()
    return sb.toString()
    }b
    fun main(args: Array) {c
    val s = buildString {
    this.append("Hello, ")
    append("World!")
    }d
    }e
    

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15. val taco = Taco()
    with(taco) {
    println(name)
    println(tasty)
    }
    

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16. fun with(
    receiver: T,
    block: T.() -> R
    ): R {
    return receiver.block()
    }
    

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17. When do we seal the casting?
    

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18. interface BinaryNumber
    object Zero : BinaryNumber
    object One : BinaryNumber
    

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19. interface BinaryNumber
    object Zero : BinaryNumber
    object One : BinaryNumber
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    else -> throw IllegalStateException()
    }c
    }d
    

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20. interface BinaryNumber
    object Zero : BinaryNumber
    object One : BinaryNumber
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    }c
    }d
    

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21. interface BinaryNumber
    object Zero : BinaryNumber
    object One : BinaryNumber
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    else -> throw IllegalStateException()
    }c
    }d
    

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22. interface BinaryNumber
    object Zero : BinaryNumber
    object One : BinaryNumber
    class Magic() : BinaryNumber() {
    fun abracadabra() {
    // ...
    }
    }
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    else -> throw IllegalStateException()
    }c
    }d
    

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23. interface BinaryNumber
    object Zero : BinaryNumber
    object One : BinaryNumber
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    else -> throw IllegalStateException()
    }c
    }d
    

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24. sealed class BinaryNumber
    object Zero : BinaryNumber()
    object One : BinaryNumber()
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    else -> throw IllegalStateException()
    }c
    }d
    

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25. sealed class BinaryNumber
    object Zero : BinaryNumber()
    object One : BinaryNumber()
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    }c
    }d
    

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26. sealed class BinaryNumber
    object Zero : BinaryNumber()
    object One : BinaryNumber()
    class Magic() : BinaryNumber() {z
    fun abracadabra() {w
    // ...
    }t
    }r
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    }c
    }d
    

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27. sealed class BinaryNumber
    object Zero : BinaryNumber()
    object One : BinaryNumber()
    class Magic() : BinaryNumber() {z
    fun abracadabra() {w
    // ...
    }t
    }r
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    }c
    }d
    

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28. sealed class BinaryNumber
    object Zero : BinaryNumber()
    object One : BinaryNumber()
    class Magic() : BinaryNumber() {z
    fun abracadabra() {w
    // ...
    }t
    }r
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    is Magic -> this.abracadabra()
    }c
    }d
    

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29. sealed class BinaryNumber
    object Zero : BinaryNumber()
    object One : BinaryNumber()
    class Magic() : BinaryNumber() {
    fun abracadabra() {
    // ...
    }
    }
    fun BinaryNumber.toInt():Int {a
    return when (this) {b
    is One -> 1
    is Zero -> 0
    is Magic -> this.abracadabra()
    }c
    }d
    

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30. View Slide

31. fun requireNotNull(obj: Any?) {a
    if (obj == null) throw IllegalArgumentException()
    }d
    

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32. fun requireNotNull(obj: Any?) {a
    if (obj == null) throw IllegalArgumentException()
    }d
    fun foo(s: String?) {e
    requireNotNull(s)
    s.length
    }f
    

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33. fun requireNotNull(obj: Any?) {a
    contract { returns() implies (obj != null) }c
    if (obj == null) throw IllegalArgumentException()
    }d
    fun foo(s: String?) {e
    requireNotNull(s)
    s.length
    }f
    

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35. Error is Ever the Sequence of Haste
    

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36. people // List
    

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37. people // List
    .map(People::name)
    .filter { it.startsWith("J") }
    

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38. people // List
    .map(People::name) // List
    .filter { it.startsWith("J") } // List
    

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39. people // List
    .asSequence()
    .map(People::name)
    .filter { it.startsWith("J") }
    

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40. people // List
    .asSequence() // Sequence
    .map(People::name) // Sequence
    .filter { it.startsWith("J") } // Sequence
    

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41. people // List
    .asSequence() // Sequence
    .map(People::name) // Sequence
    .filter { it.startsWith("J") } // Sequence
    .toList() // List
    

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42. people
    .map(People::name)
    .find { it.startsWith("J") }
    

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43. people
    .map(People::name)
    .find { it.startsWith("J") }
    And Car Jes Wil Pir
    A C J W P
    A C J
    

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44. people.asSequence()
    .map(People::name)
    .find { it.startsWith("J") }
    And Car Jes Wil Pir
    A C J
    A C J
    

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46. Generics at runtime
    

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47. fun sumUp(items: Collection<*>) {a
    if (items is List) {d
    println(ints.sum())
    }b
    }c
    val strings: List = listOf("a", "b")
    sumUp(strings)
    

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48. fun sumUp(items: Collection<*>) {a
    if (items is List) {d
    println(ints.sum())
    }b
    }c
    val strings: List = listOf("a", "b")
    sumUp(strings)
    

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49. fun sumUp(items: Collection<*>) {a
    val ints = items as? List ?: return
    println("We got a list of ints")
    println(ints.sum())
    }c
    val strings: List = listOf("a", "b")
    sumUp(strings)
    

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50. fun sumUp(items: Collection<*>) {a
    val ints = items as? List ?: return
    println("We got a list of ints")
    println(ints.sum())
    }c
    val strings: List = listOf("a", "b")
    sumUp(strings)
    -----
    We got a list of ints
    Exception in thread "main" java.lang.ClassCastException:
    java.lang.String cannot be cast to java.lang.Number
    

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51. fun sumUp(items: Collection<*>) {a
    val ints = items as? List ?: return
    println("We got a list of ints")
    println(ints.sum())
    }c
    val strings: List = listOf("a", "b")
    sumUp(strings)
    

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52. fun sumUp(items: Collection) {a
    val ints = items as? List ?: return
    println("We got a list of ints")
    println(ints.sum())
    }c
    val strings: List = listOf("a", "b")
    sumUp(strings)
    

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54. fun Iterable<*>.filterIsInstance(): List {a
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    

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55. fun Iterable<*>.filterIsInstance(): List {a
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    listOf("a", 1, 0x0, 2L, 'u')
    .filterIsInstance()
    

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56. fun Iterable<*>.filterIsInstance(): List {a
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    listOf("a", 1, 0x0, 2L, 'u')
    .filterIsInstance()
    

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57. fun Iterable<*>.filterIsInstance(): List {a
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    listOf("a", 1, 0x0, 2L, 'u')
    .filterIsInstance()
    

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58. fun Iterable<*>.filterIsInstance(): List {a
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    

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59. View Slide

60. fun Iterable<*>.filterIsInstance(): List {a
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    

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61. inline fun Iterable<*>.filterIsInstance(): List {a
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    

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62. inline fun Iterable<*>.filterIsInstance(): List
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    

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63. inline fun Iterable<*>.filterIsInstance(): List
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    

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64. inline fun Iterable<*>.filterIsInstance(): List
    val destination = mutableListOf()
    for (element in this) {c
    if (element is T) {d
    destination.add(element)
    }p
    }e
    return destination
    }f
    listOf("a", 1, 0x0, 2L, 'u')
    .filterIsInstance()
    

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65. View Slide

66. val moshi = Moshi.Builder().build()
    moshi.adapter(String::class.java) // JsonAdapter
    

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67. val moshi = Moshi.Builder().build()
    moshi.adapter(String::class.java)
    

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68. val moshi = Moshi.Builder().build()
    moshi.adapter()
    

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69. inline fun Moshi.adapter(): JsonAdapter {a
    return this.adapter(T::class.java)
    }b
    val moshi = Moshi.Builder().build()
    moshi.adapter()
    

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71. If you really want to grow as a Klass,
    you've got to learn to delegate
    

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72. class canTbeextended
    open class canbeextended
    

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73. class CountingSet(
    val innerSet: MutableCollection = HashSet()
    ) : MutableCollection {abcdefgh
    }t
    

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74. class CountingSet(
    val innerSet: MutableCollection = HashSet()
    ) : MutableCollection {abcdefgh
    var objectsAdded = 0
    }t
    

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75. class CountingSet(
    val innerSet: MutableCollection = HashSet()
    ) : MutableCollection {abcdefgh
    var objectsAdded = 0
    override fun add(element: T): Boolean {w
    objectsAdded++
    return innerSet.add(element)
    }p
    override fun addAll(c: Collection): Boolean {o
    objectsAdded += c.size
    return innerSet.addAll(c)
    }k
    }t
    

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76. class CountingSet(
    val innerSet: MutableCollection = HashSet()
    ) : MutableCollection {abcdefgh
    var objectsAdded = 0
    override fun add(element: T): Boolean {w
    objectsAdded++
    return innerSet.add(element)
    }p
    override fun addAll(c: Collection): Boolean {o
    objectsAdded += c.size
    return innerSet.addAll(c)
    }k
    }t
    

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77. class CountingSet(
    val innerSet: MutableCollection = HashSet()
    ) : MutableCollection {abcdefgh
    var objectsAdded = 0
    override fun add(element: T): Boolean {w
    objectsAdded++
    return innerSet.add(element)
    }p
    override fun addAll(c: Collection): Boolean {o
    objectsAdded += c.size
    return innerSet.addAll(c)
    }k
    override val size: Int
    get() = innerSet.size
    override fun contains(element: T): Boolean {
    return innerSet.contains(element)
    }
    override fun containsAll(elements: Collection): Boolean {
    return innerSet.containsAll(elements)
    }
    override fun isEmpty(): Boolean {
    return innerSet.isEmpty()
    }
    override fun clear() {
    innerSet.clear()
    }
    override fun iterator(): MutableIterator {
    return innerSet.iterator()
    }
    override fun remove(element: T): Boolean {
    return innerSet.remove(element)
    }
    override fun removeAll(elements: Collection): Boolean {
    return innerSet.removeAll(elements)
    }
    override fun retainAll(elements: Collection): Boolean {
    return innerSet.retainAll(elements)
    }
    }t
    

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78. class CountingSet(
    val innerSet: MutableCollection = HashSet()
    ) : MutableCollection {abcdefgh
    var objectsAdded = 0
    override fun add(element: T): Boolean {w
    objectsAdded++
    return innerSet.add(element)
    }p
    override fun addAll(c: Collection): Boolean {o
    objectsAdded += c.size
    return innerSet.addAll(c)
    }k
    }t
    

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79. class CountingSet(
    val innerSet: MutableCollection = HashSet()
    ) : MutableCollection by innerSet {abcdefgh
    var objectsAdded = 0
    override fun add(element: T): Boolean {w
    objectsAdded++
    return innerSet.add(element)
    }p
    override fun addAll(c: Collection): Boolean {o
    objectsAdded += c.size
    return innerSet.addAll(c)
    }k
    }t
    

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80. class CountingSet(
    val innerSet: MutableCollection = HashSet()
    ) : MutableCollection by innerSet {abcdefgh
    var objectsAdded = 0
    override fun add(element: T): Boolean {w
    objectsAdded++
    return innerSet.add(element)
    }p
    override fun addAll(c: Collection): Boolean {o
    objectsAdded += c.size
    return innerSet.addAll(c)
    }k
    }t
    

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82. class Foo {
    val data: Int by lazy {
    computeStuff()
    }
    }
    • lazy
    • observable
    • vetoable
    • notNull
    

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83. The Secret of Success of to
    Triple Your Quotes
    

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84. """(.+)"(.+)"(.+)""".toRegex()
    new Regex("(.+)\"(.+)\"(.+)")
    "C:\\Users\\yole\\kotlin-book" """C:\Users\yole\kotlin-book"""
    """${'$'}99.9"""
    "\$99.9"
    "$99.9"
    Java Kotlin
    

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85. assertThat(toString(taco)).isEqualTo(""
    + "package com.squareup.tacos\n"
    + "\n"
    + "import kotlin.String\n"
    + "\n"
    + "class Taco {\n"
    + " final override fun toString(): String = \"taco\"\n"
    + "}\n"
    + "")c
    

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86. assertThat(toString(taco)).isEqualTo("""
    package com.squareup.tacos
    import kotlin.String
    class Taco {
    final override fun toString(): String = "taco"
    }z
    """)c
    

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87. assertThat(toString(taco)).isEqualTo("""
    package com.squareup.tacos
    import kotlin.String
    class Taco {
    final override fun toString(): String = "taco"
    }z
    """)c
    

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88. assertThat(toString(taco)).isEqualTo("""
    |package com.squareup.tacos
    |
    |import kotlin.String
    |
    |class Taco {
    | final override fun toString(): String = "taco"
    |}z
    |""")c
    

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89. assertThat(toString(taco)).isEqualTo("""
    |package com.squareup.tacos
    |
    |import kotlin.String
    |
    |class Taco {
    | final override fun toString(): String = "taco"
    |}
    |""".trimMargin())c
    

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91. And if you want these kind of dreams
    it's Deprecation
    

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92. class SomeList {a
    fun remove(index: Int) {b
    }c
    }f
    

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93. class SomeList {a
    fun remove(index: Int) {b
    }c
    fun removeAt(index: Int) {d
    }e
    }f
    

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94. class SomeList {a
    @Deprecated("Use removeAt(index) instead.")h
    fun remove(index: Int) {b
    }c
    fun removeAt(index: Int) {d
    }e
    }f
    

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95. class SomeList {a
    @Deprecated("Use removeAt(index) instead.",
    ReplaceWith("removeAt(index)"))h
    fun remove(index: Int) {b
    }c
    fun removeAt(index: Int) {d
    }e
    }f
    

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96. class SomeList {a
    @Deprecated("Use removeAt(index) instead.",
    ReplaceWith("removeAt(index)"))h
    fun remove(index: Int) {b
    }c
    fun removeAt(index: Int) {d
    }e
    }f
    

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97. Live Demo
    

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98. View Slide