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Mapped&TypeͱPla+orm&Typeͷ
@RyotaMurohoshi
2016/12/13(Ր))ୈ4ճKotlinษڧձ)ˏ)Sansan
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ࣗݾհ
• ྄ࣨଠ(ΉΖ΄͠)
• @RyotaMurohoshi
• ࣄͰKotlin+Android
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·ͣ؆୯ʹPla$orm(TypeͷΛͯ͠
ͦͷޙMapped&TypeͷΛ͠·͢
ʰ(Mutable)List!ʱܕͱ͔ͷ
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ͬͦ͘͞ԣಓʹͦΕ·͕͢
String?String!ɺͳΜͯಡΈ·͢ʁ
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͞Βͬͱཧղ͢ΔPla$orm(Type
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ʰKotlinͩͬͨΒɺઈରNullPointerExep/onى͖ͳ͍ʱ
͜Εؒҧ͍ʂ
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Kotlinͱnull
// ίϯύΠϧΤϥʔ
val string : String = null
// ͜ΕOK
val string : String? = null
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String?Λฦ͕ؔ͋ͬͯ͢
fun loadMessage(): String? = /*ུ*/
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// OK
val message : String? = loadMessage()
// ίϯύΠϧΤϥʔ
val message : String = loadMessage()
// Nullableܕ?.Ͱͳ͍ͱϝϯόΞΫηεͰ͖ͳ͍
// ͠message͕nullͳΒmessage?.lengthnull
println(message?.length)
// ίϯύΠϧΤϥʔ
println(message.length)
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Kotlin͚ͩͳΒ
ͦ͏ͦ͏NullPointerExcep/onى͖ͳ͍
࣮Kotlin͚ͩͰNullPointerExcep0onग़ͤΔΒ͍͠
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Java͔ΒདྷͨΦϒδΣΫτʁ
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Java͔ΒདྷͨΦϒδΣΫτͷ͍ํΛؒҧ͑Δͱ
NullPointerExcep/onͱ͔IllegalStateExcep/onʹͳΔ
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Pla$orm(Type
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ݪଇJava͔ΒདྷͨΦϒδΣΫτPla&orm*Type
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Javaͷίʔυ
public class Utility {
public static String loadMessage() {
/* ུ */
}
}
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Kotlinͷίʔυ
// IDEͩͱʮString!ʯͬͯදࣔ͞ΕΔ Platform Type
val message = Utility.loadMessage()
// String?ܕʹɻString!String?ʹೖՄ
val message : String? = Utility.loadMessage()
// StringܕʹɻString!StringʹೖՄ
val message : String = Utility.loadMessage()
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ҙ
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IllegalStateExcep,onʹͳΔྫ
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IllegalStateExcep,onʹͳΔྫ
// Platform TypeͷString!ܕΛStringܕʹೖͨ࣌͠ɺ
// ͦͷΦϒδΣΫτ͕nullͳΒIllegalStateException
val message: String = Utility.loadMessage()
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NullPointerExcep/onʹͳΔྫ
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NullPointerExcep/onʹͳΔྫ
// String!ܕ
val message = Utility.loadMessage()
// Platform TypeͷString!ܕͷϝϯόʹΞΫηεͨ࣌͠ɺ
// ͦͷΦϒδΣΫτ͕nullͩͬͨΒNullPointerException
println(message.length)
// ͜ΕͳΒOKɻnullʹͳΔ
println(message?.length)
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ίϯύΠϧΤϥʔʹͳΒͳͯ͘
࣮ߦ࣌ʹΤϥʔʹͳΔ͔Βҙʂ
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@Nullable@NotNullΛ͏·͓͘͏ʂ
@NullableΛ͚ͭͨJavaͷStringString?
@NotNullΛ͚ͭͨJavaͷStringString
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ۦ͚ͰPla$orm(Type
ৄ͘͠ɺQiitaͷΞυϕϯτΧϨϯμʔݟͯͶ
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ͱ͜ΖͰPla$orm(TypeΫϥεܕͷ
͡Ό͋intͱ͔doubleͱ͔booleanͱ͔ɺ
primi%veͲ͏ͳΔʁ
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Mapped&Type
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JavaͷintɾdoubleɾboolenͳͲ
KotlinͰɺkotlin.Intɺkotlin.Doubleɺkotlin.BooleanʹͳΓ·͢
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ݴ͍͑ΔͱJavaͷprimi(veɺ
KotlinͰݻ༗ͷTypeͱͯ͠ѻΘΕΔ
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Mapped&Type
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(͜ΕυΩϡϝϯτʹॻ͍ͯ͋ͬͨ)
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͡Ό͋JavaͷIntegerͱ͔Doubleͱ͔Boolenͱ͔ɺ
primi%veܕͷϥούʔܕKotlin͔ΒͲ͏ݟ͑Δʁ
(ͳ͔ͥυΩϡϝϯτʹͳ͔ͬͨ)
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JavaͷInteger
KotlinͰInt!
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Javaͷίʔυ
public class JInts {
public static Integer getWrapperInteger() {
return /*ུ*/;
}
}
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Kotlinͷίʔυ
// numPlatform TypeͷInt!ܕ
val num = JInts.getWrapperInteger()
ѻ͍ํΛؒҧ͑ͨΒIllegalStateExcep,onʹͳͬͨΓɺNullPointerExcep,onʹͳͬͨΓ
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ଞͷPla$orm(Typeͱಉ༷ʹ
@Nullable@NotNullΛ͓͏
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Javaͷίʔυ
public class JInts {
public static Integer getWrapperInteger() { return /*ུ*/; }
@Nullable
public static Integer getWrapperIntegerNullable() { return /*ུ*/; }
@NotNull
public static Integer getWrapperIntegerNotNull() { return /*ུ*/; }
}
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Kotlinͷίʔυ
// numPlatform TypeͷInt!ܕ
val num = JInts.getWrapperInteger()
// numInt?ܕ
val num = JInts.getWrapperIntegerNullable()
// numIntܕ
val num = JInts.getWrapperIntegerNotNull()
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ͳΔ΄Ͳ
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ͰٯʹɺKotlinͷInt?Double?Java͔ΒͲ͏ݟ͑Δʁ
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KotlinͷInt?
JavaͰInterger
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Kotlinͷίʔυ
class KInts {
companion object {
@JvmStatic
fun getInt(): Int = 0
@JvmStatic
fun getNullableInt(): Int? = 0
}
}
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Javaͷίʔυ
public class KIntsUsage {
public static void main(String[] args) {
int num0 = KInts.getInt();
Integer num1 = KInts.getNullableInt();
// ΞϯϘΫγϯάͰ͜͏͔͚Δ
int num2 = KInts.getNullableInt();
}
}
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KotlinͷInt?
JavaͰInterger
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ͳΔ΄Ͳ
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Mapped&Type࣮primi,ve͚ͩ͡Όͳͯ͘ࢀরܕʹ͋Δ
• java.lang.Enum,<.>,kotlin.Enum!
• java.lang.Void,<.>,kotlin.Nothing!
• java.lang.String,<.>,kotlin.String!
• java.lang.Number,<.>,kotlin.Number!
࣮Stringʂʂʂ
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࠷ޙʹ
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ʰ(Mutable)List!ʱͱʁ
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Mapped&TypeͱPla+orm&Typeͷ߹Θٕͤ
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Kotlinͷ
2ͭͷϦετΠϯλʔϑΣʔε
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kotlin.collec*ons.List
count()ͱ͔ཁૉऔಘͱ͔ReadOnlyͳϝιου͔͠ͳ͍
(ͪͳΈʹListΠϛϡʔλϒϧͰͳ͍)
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kotlin.collec*ons.MutableList
ListΛܧঝ͠͞ΒʹཁૉΛมߋ͢ΔϝιουΛ࣋ͭ
(clearͱ͔addͱ͔Ͱ͖Δ)
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ͲͪΒJavaͰ
java.u&l.List
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Kotlinͷίʔυ
class KLists {
companion object {
@JvmStatic
fun getStringList(): List = listOf("")
@JvmStatic
fun getMutableStringList(): MutableList = mutableListOf("")
}
}
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Javaͷίʔυ
List list0 = KLists.getStringList();
List list1 = KLists.getMutableStringList();
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ͰJavaͷjava.u'l.List
Kotlin͔ΒͲ͏ݟ͑Δ?
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Javaͷίʔυ
public class JLists {
public static List getList() {
return new ArrayList<>();
}
}
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Kotlinͷίʔυ
// IDEͰͷදࣔʰ(Mutable)List!ʱܕ
val list = JLists.getList()
println(list.count)
// MutableListͷϝιου͕asͳ͠ͰݺΔ
list.clear()
println(list.count)
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MutableList͡Όͳͯ͘Listͱͯ͠ѻ͍͍ͨ߹ʁ
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@ReadOnly
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@ReadOnlyͱ@MutableΛ༩ͨ͠Javaͷίʔυ(@NotNull)
public class JLists {
@NotNull
@ReadOnly
public static List getReadonlyList() {
return new ArrayList<>();
}
@NotNull
@Mutable
public static List getMutableList() {
return new ArrayList<>();
}
}
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Kotlinͷίʔυ
// kotlin.collections.List
val list = JLists.getReadonlyList()
// ͜ΕOK
val list : List = JLists.getReadonlyList()
// ίϯύΠϧΤϥʔ
val list : MutableList = JLists.getReadonlyList()
println(list.count()) // OK
list.clear() // ίϯύΠϧΤϥʔ
@ReadOnlyͱ@MutableΛ͚ͭΔ͜ͱͰมԽ
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// kotlin.collections.MutableList
val list = JLists.getMutableList()
// ͜ΕOK
val list : MutableList = JLists.getMutableList()
println(list.count()) // OK
list.clear() // OK
// MutableListListΛܧঝ͍ͯ͠ΔͷͰɺͭ͜͡ΕOK
// ͨͩclearͱ͔addݺͳ͍
// val list : List = JLists.getMutableList()
@ReadOnlyͱ@MutableΛ͚ͭΔ͜ͱͰมԽ
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͜ΕΒList͚ͩͰͳ͘
SetMapͰ͍ͬ͠ΐ
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·ͱΊ
Pla$orm(TyoeͱMapped(Type
ཧղ͓ͯ͜͠͏ʂ