ϓϩάϥϛϯάݴޠ Kotlinͷ঺հ ૣҴాେֶཧ޻ֶज़Ӄ ίϯϐϡʔλ࠙࿩ձ 
 ௕ᖒଠ࿠!OHTX@UBSP ͜ͱΓΜ

ࣗݾ঺հ w ௕ᖒଠ࿠!OHTX@UBSP w ਂᖒݚڀࣨ೥ଔۀ ֶ෦ w ࣗশ,PUMJOΤόϯδΣϦετ w ޷͖ͳ΋ͷɺ

ΞδΣϯμ +BWBͰ๊͑Δ໰୊ ,PUMJOొ৔

1. JavaͰ๊͑Δ໰୊

w ߴੑೳɾߴ৴པੑͷ+BWBԾ૝Ϛγϯ w ਐԽΛଓ͚Δϓϩάϥϛϯάݴޠ w ͔͠΋ޙํޓ׵ੑΛҡ࣋ w ྺ࢙௕͍ɺਓޱଟ͍ w ϥΠϒϥϦɾϑϨʔϜϫʔΫଟ͍ Javaૉఢ

w ৑௕ɺϘΠϥʔϓϨʔτ w OVMMϙΠϯλͷٯࢀর໰୊ w ܕ҆શੑͷ໰୊ ͔͠͠ɺͦͷ൓໘

৑௕ MyFavoriteService s =! new MyFavoriteService<>(banana);

ϘΠϥʔϓϨʔτ public final class Fruit {! ! private final String name;! ! private final int price;! ! private final Country country;! ! public Fruit(final String name, final int price, final Country country) {! this.name = name;! this.price = price;! this.country = country;! }! ! public String getName() {! return name;! }! ! public int getPrice() {! return price;! }! ! public Country getCountry() {! return country;! }! ! public Fruit withName(final String name) {! return new Fruit(name, price, country);! }! ! public Fruit withPrice(final int price) {! return new Fruit(name, price, country);! }! ! public Fruit withCountry(final Country country) {! return new Fruit(name, price, country);! }! ! // toStringͱ͔! // equalsͱ͔! // hashCodeͱ͔! ! public static Builder builder() {! return new Builder();! }! ! public static class Builder {! ! private String name;! ! private int price;! ! private Country country;! ! public Fruit build() {! return new Fruit(name, price, country);! }! ! public Builder name(final String name) {! this.name = name;! return this;! }! ! public Builder price(final int price) {! this.price = price;! return this;! }! ! public Builder country(final Country country) {! this.country = country;! return this;! }! }! } 'SVJUͷఆٛ w QSJWBUFpOBMϑΟʔϧυ w ίϯετϥΫλ w HFUUFS w UP4USJOH FRVBMT IBTI$PEF w #VJMEFSΫϥε

nullϙΠϯλͷٯࢀর String s = null;! s.toUpperCase(); /VMM1PJOUFS&YDFQUJPO

NPE͕ݏͳΒ nullνΣοΫ͢Ε͹͍͍͡Όͳ͍ String s = Ṗͷϝιου();! String upperCase = (s != null)! ? s.toUppserCase()! : null;

ͦΕຊ౰ʁ String s = reverse("Hello");! String upperCase = (s != null)! ? s.toUppserCase()! : null;

ͦΕຊ౰ʁ String s = reverse("Hello");! String upperCase = (s != null)! ? s.toUppserCase()! : null; OVMM͸ฦ͞ͳͦ͏ɻ ͱ͍͏͔࣮ࡍฦ͞ͳ͍

nullͳͷ͔ null͡Όͳ͍ͷ͔ Θ͔Βͳ͍

ͱΓ͋͑ͣJavaతͳ޻෉ @Nonnull! String reverse(String s) {…}! ! ! Optional! initial(String s) {…}

୭ʹ΋null͸ࢭΊΒΕͳ͍ʂ @Nonnull! Optional findFoo() {! return null;! }

ܕ҆શੑͷ໰୊ Integer[] ints = { 0 };! Number[] nums = ints;! nums[0] = 0.5;

ܕ҆શੑͷ໰୊ Integer[] ints = { 0 };! Number[] nums = ints;! nums[0] = 0.5; ໌Β͔ʹϚζ͍ૢ࡞ͳͷʹ ίϯύΠϥ͸ؾ෇͔ͳ͍

ܕ҆શ͚ͩͲ List ints = immutableListOf(1);! ! List extends Number> nums = ints; ڞมͷ໌ࣔతͳࢦఆ ৑௕

w ΋ͬͱ୹͘ɺಡΈ΍͍͢ίʔυΛॻ͖ ͍ͨ w ҆શͳίʔυΛॻ͖͍ͨɻةݥͳίʔ υ͸ίϯύΠϧλΠϜʹ஄͍ͯཉ͍͠ ࢥ͏͜ͱ

2. Kotlinొ৔

w ೥Նʹ+FU#SBJOTʹΑΓൃද w Φʔϓϯιʔε "QBDIF-JDFOTF w +7.ݴޠɺBMU+4ɺ"OESPJE΋αϙʔτ w +BWBࢿ࢈Λ׆͔ͤΔ w ੩తܕ෇͚ΦϒδΣΫτࢦ޲ݴޠ Kotlinͱ͸

w ৑௕ɺϘΠϥʔϓϨʔτ w OVMMϙΠϯλͷٯࢀর໰୊ w ܕ҆શੑͷ໰୊ Kotlinͷ౴͑

ܕਪ࿦ // Java! MyFavoriteService s =! new MyFavoriteService<>(banana);! ! ! // Kotlin! val s = MyFavoritesService(banana)

ϘΠϥʔϓϨʔτ public final class Fruit {! ! private final String name;! ! private final int price;! ! private final Country country;! ! public Fruit(final String name, final int price, final Country country) {! this.name = name;! this.price = price;! this.country = country;! }! ! public String getName() {! return name;! }! ! public int getPrice() {! return price;! }! ! public Country getCountry() {! return country;! }! ! public Fruit withName(final String name) {! return new Fruit(name, price, country);! }! ! public Fruit withPrice(final int price) {! return new Fruit(name, price, country);! }! ! public Fruit withCountry(final Country country) {! return new Fruit(name, price, country);! }! ! // toStringͱ͔! // equalsͱ͔! // hashCodeͱ͔! ! public static Builder builder() {! return new Builder();! }! ! public static class Builder {! ! private String name;! ! private int price;! ! private Country country;! ! public Fruit build() {! return new Fruit(name, price, country);! }! ! public Builder name(final String name) {! this.name = name;! return this;! }! ! public Builder price(final int price) {! this.price = price;! return this;! }! ! public Builder country(final Country country) {! this.country = country;! return this;! }! }! } data public class Fruit(! val name: String,! val price: Int,! val country: Country! )

nullϙΠϯλͷٯࢀর // Java! String s = null;! s.toUpperCase();! ! // Kotlin! val s1: String = null! val s2: String? = null! s2.toUppserCase()

nullϙΠϯλͷٯࢀর // Java! String s = null;! s.toUpperCase();! ! // Kotlin! val s1: String = null! val s2: String? = null! s2.toUppserCase() /1&

nullϙΠϯλͷٯࢀর // Java! String s = null;! s.toUpperCase();! ! // Kotlin! val s1: String = null! val s2: String? = null! s2.toUppserCase() ίϯύΠϧΤϥʔ ௨ৗͷܕͷม਺ʹɺ OVMM͸୅ೖͰ͖ͳ͍

nullϙΠϯλͷٯࢀর // Java! String s = null;! s.toUpperCase();! ! // Kotlin! val s1: String = null! val s2: String? = null! s2.toUppserCase() ܕ ͸OVMMͰ΋0,

nullϙΠϯλͷٯࢀর // Java! String s = null;! s.toUpperCase();! ! // Kotlin! val s1: String = null! val s2: String? = null! s2.toUppserCase() ίϯύΠϧΤϥʔ ܕ ʹର͢Δٯࢀর͸ ؾܰʹͰ͖ͳ͍ʂ

KotlinͰ͸ null͔൱͔Λ໌֬ ʹ۠ผ͢Δ ࢀߟIUUQTTQFBLFSEFDLDPNOUBSPLPUMJOOVNCFSTIJCVJHVKWN

ܕ҆શ val ints: Array = arrayOf(0)! ! val nums: Array = ints ίϯύΠϧΤϥʔ +BWBελΠϧͷ഑ྻ͸ͳ͍ɻ δΣωϦΫεͰදݱɻ

ܕࣗମʹมҐࢦఆͰ͖Δ val ints: List = listOf(0)! ! val nums: List = ints JOUFSGBDF-JTUPVU& ͷΑ͏ʹܕͷఆٛ࣌ʹ มҐΛࢦఆͰ͖Δ

w ͔ͳΓ୹͘ɺಡΈ΍͍͢ίʔυ͕ॻ͚ ͦ͏ɻ w ܕͷҧ͍΍OVMMʹΑΔ࣮ߦ࣌ΤϥʔΛ๷ ͍Ͱ҆શͳίʔυ͕ॻ͚ͦ͏ɻ ࢥ͏͜ͱ

ͦͷଞͷಛ௕ w ֦ுؔ਺੩తʹطଘܕʹϝιουΛੜ΍ͤ ΔΑ͏ͳ΍ͭ w ߴ֊ؔ਺ɺؔ਺ΦϒδΣΫτɺϥϜμࣜ w +BWBͱͷ૬ޓӡ༻ੑ ໨ඪ w +BWBͱಉ౳ͷίϯύΠϧ଎౓ ໨ඪ w "OESPJE։ൃΛެࣜαϙʔτ

w ҆ఆ൛ະϦϦʔε ݱࡏWFS w *%&ͷิॿ͕+BWBͱൺֱͯ͠·ͩऑ͍ w ਓޱɺೝ஌౓͕े෼Ͱͳ͍ ୹ॴ

·ͱΊ JavaͰ΋ΜʹΐΓ͢ Δͱ͜ΖɺKotlinͰ͸ ΠΠײ͡ʹͳͬͯΔΑ

w IUUQUSZLPUMJOMBOHPSH w खܰʹࢼͤΔ࣮ߦ؀ڥ w ͪΐͬͱ͚ͩಋೖ w ςετίʔυ͚ͩɺ6UJMతͳ΍͚ͭͩ w +BWBͱͷڞଘ͕༰қͳͷͰ ·ͣ࢝ΊΑ͏

͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ Let’s enjoy Kotlin!