パターンマッチングを学んで新しいJavaの世界へ！Java 18までの目玉機能をおさらいしよう / Java 18 pattern matching

Transcript

1. ύλʔϯϚονϯάΛֶΜͰ ৽͍͠+BWBͷੈք΁ʂ +BWB
   ·Ͱͷ໨ۄػೳΛ ͓͞Β͍͠Α͏ 
   ++6(
   $$$
   
   4QSJOH
2. Θͨ͠ • Α͜ͳ !JIDPNFHB • %FWFMPQFS
   "EWPDBUF
   !
   +'SPH • ݩ͸ݱ৔ͷόοΫΤϯυΤϯδχΞ • ʰ͍ͪ͹Μ΍͍͞͠(JU(JU)VCͷڭՊॻʱ • ࠷ۙεΧΠμΠϏϯάΛͨ͠ 1
3. ϦϦʔεαΠΫϧ͕มΘͬͨͷ͸ ೥݄ +BWB
   ͔Β ΋͏೥͕ܦա͠Α͏ͱͯ͠Δʜ 2
4. ΩϟονΞοϓͷ ਐḿͲ͏Ͱ͔͢ʁ 3
5. Ξοϓσʔτͷྫ +BWB
    var nanikore = Map.of( 1, List.of("いぬ", "ねこ", "たぬき"), 2, List.of("こあら", "ぱんだ")); ϩʔΧϧม਺ͷ ܕਪ࿦ 4
6. Ξοϓσʔτͷྫ +BWB
    String memo = """ %s 以降 テキストブロックで 複数⾏の⽂字が 書けるようになった """.formatted("Java 15"); ςΩετϒϩοΫ 5
7. Ξοϓσʔτͷྫ +BWB
    if (sth instanceof String s) { System.out.println(s); } JOTUBODFPGʹΑΔ ύλʔϯ Ϛονϯά 6
8. ෼͔Γ΍͍͢΋ͷɺ ΠϚΠνԿ͕خ͍͠ͷ͔ ௫ΈͮΒ͍΋ͷ ৭ʑ͋ΔΑͶ 7
9. ࠓ೔ͷςʔϚ͸ ύλʔϯϚονϯά 8
10. ͡Θ͡ΘਐΉػೳ֦ுʹΑΓ ݟ͑ͮΒ͘ͳ͍ͬͯΔ͔΋ ͠Εͳ͍ศར͞Λ Ұॹʹֶ΅͏ʂ 9
11. ͜ͷηογϣϯͰ஌Ζ͏ • ύλʔϯϚονϯά • +BWB
    ·ͰΛ࢖ͬͨύλʔϯϚονϯά • +BWB
    Ҏ߱ͰͷਐԽ • 1SPKFDU
    "NCFS΍ϦϦʔεαΠΫϧ 10
12. ύλʔϯϚονϯάͱ͸ Ұൠ࿦ • ෼͔Γ΍͘͢ݴ͏ͱ৚݅൑ఆͷͻͱͭ • ஋Λύλʔϯͱর߹͠ɺҰக Ϛον ͢Δ͔֬ೝ͢Δ • Ұக͔ͨ͠Ͳ͏͔Ͱ৚݅Λ෼ذͨ͠Γɺ஋Λ෼ղͯ͠ ࢖ͬͨΓ͢Δ͜ͱ΋Ͱ͖Δ 11
13. ύλʔϯϚονϯάͱ͸ Ұൠ࿦ “Ն” “य़” “Ն” “ळ” “ౙ” 12
14. ύλʔϯϚονϯάͱ͸ Ұൠ࿦ 🌻 🌹 🌸 🌷 🌸 🌸 🌸 🌸 🌷 🌹 🌻 🌸 🌻 🌹 🌸 🌷 🌻 🌹 ❓ ❓ 💐 💐 💐 💐 13
15. ύλʔϯϚονϯάͱ͸ 🌻 🌹 🌸 🌷 🌻 🌹 ❓ 🌷 B
    ʹ 🌹 র߹ ෼ղ C
    ʹ 🌸 14
16. +BWB
    ͰύλʔϯϚονϯά • TXJUDIࣜ • JOTUBODFPGΛ࢖ͬͨύλʔϯϚονϯά • TXJUDIΛ࢖ͬͨύλʔϯϚονϯά • Ϩίʔυ 3FDPSE • γʔϧΫϥε 4FBMFE
    DMBTT +BWB
    ͔Β গͣͭ͠ ಋೖ͞Ε͍ͯΔΑ 15
17. ͲͷόʔδϣϯͰԿ͕ೖ͔ͬͨ͸ ͍ͬͨΜ๨Εͯɺ +BWB
     ϓϨϏϡʔؚΉ
    ͰͰ͖Δ͜ͱ Λ ·ͣ͸஌Ζ͏ 16
18. ϓϨϏϡʔػೳͱ͸ • ਖ਼ࣜϦϦʔεલͷػೳ • ࣮ࡍʹ࢖ͬͯͷϑΟʔυόοΫΛಘΔͨΊެ։͞ΕΔ • KBWBD΍KBWBίϚϯυʹ FOBCMFQSFWJFX
    ϑϥάΛ ෇͚࣮ͯߦ͢Δͱ༗ޮʹͳΔ • KBWBD
    SFMFBTFE
    
    FOBCMFQSFWJFX
    )PHFKBWB • KBWB
    FOBCMFQSFWJFX
    )PHF • KTIFMM΍KBWBEPDίϚϯυͰ΋࢖͑Δ • *%&Ͱ΋αϙʔτ͕͋Δ 17
19. γϯϓϧͳύλʔϯϚονϯά String season = “夏”; String result = switch (season) { case “春” -> “Spring”; case “夏” -> “Summer”; case “秋” -> “Fall”; case “冬” -> “Winter”; default -> "Nothing"; } 18
20. TXJUDIࣜ • TXJUDIΛʮࣜʯͱͯ͠࢖͑Δʢ஋Λฦ͢ʣ • ͜Ε΋ύλʔϯϚονϯάͷͻͱͭʢఆ਺ύλʔϯʣ 19
21. ΋͏গ͠ෳࡶͳྫͰ ύλʔϯϚον ϏϑΥʔΞϑλʔΛ ݟ͍ͯ͜͏ 20
22. ߟ͑Δͷʹ࢖͏αϯϓϧ ϝϞா • ςΩετϝϞ • 50%0Ϧετ • ը૾͖ͭςΩετϝϞ • શͯ*%ͱλΠτϧΛ࣋ͭ • ϝϞͷߏ଄͕֤ʑҟͳΔ 21
23. γφϦΦ ϞσϧΛ༻ҙ͢Δ ௚઀తʹ͸ ύλʔϯϚονϯάͷ ࿩Ͱ͸ͳ͍͚Ͳ ޙʑ࢖͏ͷͰ঺հ͠·͢ 22
24. ϞσϧΛ༻ҙ͢Δ • େྔͷΫϥεΛ࡞੒͢Δ • ͦͷ෼ϘΠϥʔϓϨʔτ΋ॻ͘ 23
25. ϞσϧΛ༻ҙ͢Δ چ public class Text implements Memo { private Id id; private Title title; private Body body; public Text(Id id, Title title, Body body) { this.id = id; this.title = title; this.body = body; } // setter/getter // toString() // equals() // hashCode() } 24
26. ՝୊ • ͍ͨ΁Μ 25
27. ϞσϧΛ༻ҙ͢Δ ৽ record Text(Id id, Title title, Body body) implements Memo {} 26
28. ϨίʔυΫϥε record Text(Id id, Title title, Body body) implements Memo {} • SFDPSEΩʔϫʔυ෇͖ͰΫϥεΛఆٛ͢Δ • (Id id, Title title, Body body) ෦෼
    
    ʮ Ϩίʔυ ϔομʔʯʹ ʮ Ϩίʔυ ίϯϙʔωϯτʯΛఆٛͰ͖Δ 27
29. ϨίʔυΫϥε Լه͕ࣗಈͰੜ੒͞ΕΔ • ϔομʔͱಉ͡ϑΟʔϧυΛ࣋ͬͨίϯετϥΫλ • ֤ίϯϙʔωϯτʹରͯ͠ͷ • QSJWBUF
    GJOBMͳϑΟʔϧυ ίϯϙʔωϯτͱಉ໊ • QVCMJDͳΞΫηαʔϝιου ίϯϙʔωϯτͱಉ໊ • FRVBMT ϝιου
    IBTI$PEF ϝιου ಉ͡ܕͰ֤ίϯϙʔωϯτ͕ಉ͡஋Λ࣋ͬͨϨίʔυ͔Ͳ͏͔ • UP4USJOH ϝιου
    ίϯϙʔωϯτͷ໊લͱ஋Λฦ͢ 28
30. ϨίʔυΫϥε • ϨίʔυΫϥεɺίϯϙʔωϯτ͔Βੜ੒͞ΕͨϑΟʔϧυ͸ ҉໧తʹGJOBM
    ΠϯελϯεΛΠϛϡʔλϒϧʹอͭࢥ૝ • ଞͷΫϥεΛܧঝͰ͖ͳ͍ KBWBMBOH3FDPSE
    Λܧঝ͍ͯ͠Δ ͨΊ • ΠϯλʔϑΣʔεͷ࣮૷͸Ͱ͖Δ • ଞͷΫϥε͔Βͷܧঝ΋Ͱ͖ͳ͍ GJOBMͳͷͰ • Ϋϥεͱಉ༷ϝιου͕એݴͰ͖Δ • ϔομʔҎ֎ʹΠϯελϯεϑΟʔϧυ͸એݴͰ͖ͳ͍ 29
31. ϨίʔυΫϥε public interface Memo { … record Text(Id id, Title title, Body body) implements Memo {} record TodoList(Id id, Title title, List<Task> tasks) implements Memo {} record Image … } • Ϋϥε΍ΠϯλʔϑΣʔεͷதʹఆٛͰ͖Δ • ೖΕࢠʹ͢Δ͜ͱͳ͘ಉϑΝΠϧʹఆٛ΋Ͱ͖Δ • ΋ͪΖΜผϑΝΠϧͰͷఆٛ΋Ͱ͖Δ ͜͏͢Ε͹ϑΝΠϧʹఆٛͰ͖Δ͕ QVCMJDͳϨίʔυʹ͍ͨ͠৔߹ ೖΕࢠʹ͢Δ͔͠ͳ͍ɻ ݟ׳Εͳ͍ίʔυʹͳΔ΋ͷͷศར 30
32. γφϦΦ ϏδωεϩδοΫ࣮૷ฤ ϝϞͷछྨ͝ͱʹॲཧΛৼΓ෼͚Δ 31
33. String doSomethingForEach(Memo memo) { if (memo == null) { return "nullが来た"; } else if (memo instanceof Text) { Text text = (Text) memo; return doSomethingForText(text); } else if (memo instanceof TodoList) { TodoList todo = (TodoList) memo; return doSomethingForTodoList(todo); } else if (memo instanceof Image) { Image image = (Image) memo; return doSomethingForImage(image); } else { return "おかしな値が来た"; } } ϝϞͷछྨ͝ͱʹ ॲཧΛৼΓ෼͚Δ چ 32
34. ՝୊ • JGFMTF
    ஍ࠈʹؕΔ • ܕʹΑΔ൑ఆΛߦ͏ࡍɺ൑ఆͱ࢖༻͕ผͷεςοϓʹ෼͔ΕΔ • ͭ·Γɺίʔυྔ͕΍ͨΒͱଟ͘ͳͬͯಡΈͮΒ͍ 33
35. String doSomethingForEach(Memo memo) { return switch (memo) { case null -> “nullが来た”; case Text t -> doSomethingForText(t); case TodoList td -> doSomethingForTodoList(td); case Image i -> doSomethingForImage(i); default -> "おかしな値が来た"; }; } ϝϞͷछྨ͝ͱʹ ॲཧΛৼΓ෼͚Δ ৽ 34 ໼ҹ͕ἧ͏Α͏ͳ ϑΥʔϚοτʹ͢Δͱ ಡΈ΍͍͢
36. ܕͰύλʔϯϚονϯά • ܕͰύλʔϯϚονϯάͰ͖Δ ܕʗλΠϓύλʔϯ • ܕʹϚονͨ͠Β஋͕ม਺ʹऔΓग़͞ΕΔ • ύλʔϯม਺ͱݴ͍ɺείʔϓ͸Ϛονͨ͠έʔεͷதͷΈ • Ϩίʔυͱͯ͠ఆٛ͞ΕͨܕͰ΋ύλʔϯϚονϯάͰ͖Δ 35
37. case null, Text t -> “null͔ςΩετϝϞ”; case null, default -> “null͔͓͔͠ͳ஋”; • ࠓͷͱ͜ΖҟͳΔܕΛ·ͱΊͯॻ͘͜ͱ͸Ͱ͖ͳ͍͕ɺOVMMͱ ଞͷέʔε͸·ͱΊΒΕΔ • OVMMͷ৔߹ύλʔϯม਺Λ࢖͏ͱ౰વ/VMM1PJOUFS&YDFQUJPO ϝϞͷछྨ͝ͱʹ ॲཧΛৼΓ෼͚Δ ৽ 36
38. γφϦΦ ϏδωεϩδοΫ࣮૷ฤ ͞Βʹࡉ͔͘ॲཧΛৼΓ෼͚Δ 37
39. String doSomethingForEach(Memo memo) { if (memo == null) { return “nullが来た”; } else if (memo instanceof Text) { Text text = (Text) memo; return doSomethingForText(text); } else if (memo instanceof TodoList) { TodoList todo = (TodoList) memo; if (0 < todo.tasks().size()) { return doSomethingForTodoList(todo); } else { return "ToDoが空っぽ"; } } else if (memo instanceof Image) { Image image = (Image) memo; return doSomethingForImage(image); } else { return "おかしな値が来た"; } } ৚݅Λ௥Ճ͢Δ چ 38
40. … } else if (memo instanceof TodoList) { TodoList todo = (TodoList) memo; if (0 < todo.tasks().size()) { return doSomethingForTodoList(todo); } else { return "ToDoが空っぽ"; } } else if… ৚݅Λ௥Ճ͢Δ چɾ֦େ 39
41. ՝୊ • ෳࡶ͕͞ߴ·ΓՄಡੑ͕ͲΜͲΜԼ͕Δ 40
42. return switch (memo) { case null -> "nullが来た"; case Text t -> doSomethingForText(t); case TodoList td && 0 < td.tasks().size() -> doSomethingForTodoList(td); case TodoList td -> "ToDoが空っぽ"; case Image i -> doSomethingForImage(i); default -> "おかしな値が来た"; }; ৚݅Λ௥Ճ͢Δ ৽ 41
43. ΨʔυύλʔϯʗύλʔϯΨʔυ case TodoList td && 0 < td.tasks().size() -> doSomethingForTodoList(td); case TodoList td -> "ToDoが空っぽ"; • ύλʔϯϚονϯάʹ৚݅Λ௥ՃͰ͖Δ • ৚݅ʹ߹க͠ͳ͍৔߹ͷॲཧΛॻ͖๨Εͳ͍Α͏ʹ͠Α͏ 42
44. γφϦΦ ࢓༷มߋฤ ϝϞͷछྨΛ૿΍͢ 43
45. ϝϞͷछྨΛ૿΍͢ public interface Memo { … record Text(Id id, Title title, Body body ) implements Memo {} record TodoList(Id id, Title title, List<Task> tasks) implements Memo {} record Image(Id id, Title title, ImageUrl url, Body body ) implements Memo {} record Video(Id id, Title title, VideoUrl url ) implements Memo {} } 44
46. return switch (memo) { case null -> "nullが来た"; case Text t -> doSomethingForText(t); case TodoList td && 0 < td.tasks().size() -> doSomethingForTodoList(td); case TodoList td -> "ToDoが空っぽ"; case Image i -> doSomethingForImage(i); case Video v -> doSomethingForVideo(v); default -> "おかしな値が来た"; }; ϝϞͷछྨΛ૿΍͢ 45
47. ՝୊ • ݺͼग़͠Օॴͷௐ͕ࠪେมɾݟམͱ͠ͷ΋ͱ 46
48. ϝϞͷछྨΛ૿΍͢ sealed public interface Memo { … record Text(Id id, Title title, Body body ) implements Memo {} record TodoList(Id id, Title title, List<Task> tasks) implements Memo {} record Image(Id id, Title title, ImageUrl url, Body body) implements Memo {} record Video(Id id, Title title, Video Url url) implements Memo {} } 47
49. γʔϧ υ Ϋϥε • TFBMFEΩʔϫʔυΛ͚ͭͯఆٛͨ͠Ϋϥε΍ΠϯλʔϑΣʔε • ܧঝɾ࣮૷ՄೳͳΫϥεΛԼهͷΈʹݶఆ͢Δ Ϩίʔυ΋Մ • QFSNJUT۟Λ͚ͭͯڐՄͨ͠Ϋϥε sealed public interface Memo permits Text, TodoList, Image, Video • ಉ͡ϑΝΠϧʹఆٛͨ͠Ϋϥε • ܕʹΑΔύλʔϯϚονϯάͰ͢΂ͯͷܕΛ໢ཏ͍ͯ͠Δ͜ͱ Λ୲อͰ͖Δ ໢ཏ͍ͯ͠ͳ͍৔߹͸ίϯύΠϧΤϥʔ • ύλʔϯϚονϯάʹ͓͚ΔEFGBVMU͕ඞਢͰͳ͘ͳΔ 48
50. return switch (memo) { case null -> "nullが来た"; case Text t -> doSomethingForText(t); case TodoList td && 0 < td.tasks().size() -> doSomethingForTodoList(td); case TodoList td -> "ToDoが空っぽ"; case Image i -> doSomethingForImage(i) ; case Video v -> doSomethingForVideo(v); }; ϝϞͷछྨΛ૿΍͢ 49
51. ͜͜·Ͱͷ͓͞Β͍ • ύλʔϯϚονϯάΛ׆༻ͯ͠ϘΠϥʔϓϨʔτ͕ݮΒͤΔ • ݱঢ়
    +BWBͷύλʔϯϚονϯά͸TXJUDIΛ׆༻͢Δ • ܕύλʔϯΛ࢖͏ͱ͖͸γʔϧΫϥεͰϛε΋ݮΒͤΔ • ܕΛ׆༻͢Δ্ͰϨίʔυ͸͔ܽͤͳ͍ 50
52. Ϩίʔυ͚ͩ ύλʔϯϚονϯάͱ བྷΊΔʹ͸ͪΐͬͱऑ͍ʜʁ 51 ͋ͱɺࠓ೔ͷྫͷΑ͏ʹ ෼ذޙʹ݁ہಉ͡Α͏ͳ ॲཧΛ͍ͤͨ͞৔߹ɺ ܧঝͰྑ͍ͷͰ͸ʁͱ͔
53. +BWB
    ʹظ଴ if (memo instanceof Text(Id id, Title title, Body body)) { show(body); } --- OR --- if (memo instanceof Text(var id, var title, var body)) { show(body); } • Ϩίʔυύλʔϯ͕ಋೖ͞ΕΔ༧ఆ ϓϨϏϡʔ • ϨίʔυΛ༻͍ͨύλʔϯϚονϯάʹ͓͍ͯ෼ղ͕༰қʹͳΔ 52
54. ΋ͬͱকདྷ ˞ΠϝʔδͰ͢ String doSomethingForEach(Memo memo) { return switch (memo) { case null -> "nullが来た"; case Text(Id id, Title title, Body body) -> doSomethingForText(body); case TodoList(Id id Title title, List<Task> tasks) && 0 < tasks().size() -> doSomethingForTodoList(tasks); case TodoList _ -> "ToDoが空っぽ"; case Image(Id id, Title title, ImageUrl url, Body body) -> doSomethingForImage(url, body); }; } 53
55. Ϩίʔυύλʔϯɺ෼ղ 54 • ʮͲͷܕ͔ʯͷΈͳΒͣʮͲΜͳߏ଄͔ʯΛ;·͑ͯύλʔϯ ϚονϯάͰ͖Δ • ܧঝʹΑΔϙϦϞʔϑΟζϜ͚ͩͰදݱͮ͠Β͍ෳࡶͳέʔε ʢΦʔόʔϩʔυͨ͘͠ͳͬͨ࣌ͱ͔ʣͰ͸ಛʹ׆༻Ͱ͖Δ
56. +BWB
    Ͱͷখ͞ͳมߋ case TodoList td when 0 < td.tasks().size() -> doSomethingForTodoList(td); • Ψʔυύλʔϯͷࢦఆ͕ 
    Ͱ͸ͳ͘ XIFO
    ʹมΘΔ • ෼͔Γ΍͢͞ͷͨΊΒ͍͠ 55
57. +BWBύλʔϯϚονϯάมભ         ϓϨϏϡʔ ਖ਼ࣜϦϦʔε TXJUDIࣜ JOTUBODFPG ύλʔϯϚον Ϩίʔυ γʔϧυ TXJUDI ύλʔϯϚον Ϩίʔυ ύλʔϯ 56
58. 1SPKFDU
    "NCFS • 0QFO+%,ͷ։ൃ͸ϓϩδΣΫτ୯ҐͰਐΉ • IUUQTPQFOKELKBWBOFUQSPKFDUT • ΰʔϧΛ໨ࢦͯ͠গͣͭ͠ػೳ௥Ճ͞ΕΔͷͰɺϓϩδΣΫτ ͱ͍͏୯Ґʹ஫໨͢Δͱ෼͔Γ΍͍͢ • ͜͜·Ͱ঺հͨ͠ύλʔϯϚονϯάɺςΩετϒϩοΫɺ WBS͸શ෦ʮ1SPKFDU
    "NCFSʯͷ੒Ռ • IUUQTPQFOKELKBWBOFUQSPKFDUTBNCFS • 1SPKFDU
    "NCFS͸ݴޠʹؔ͢Δػೳվળू 57
59. ࠷৽ͷ৘ใΛಘΔʹ͸ • +&1
    +%,
    &OIBODFNFOU1SPQPTBM
    ͰϩʔυϚοϓΛ֬ೝͰ͖Δ • ྫ
    TXJUDIࣜ͸+&1 
    +&1ͦͷ΋ͷͷઆ໌͸+&1  • 0QFO
    +%,ͷެࣜϖʔδΛݟΔͱ෼͔Γ΍͍͢ • IUUQTPQFOKELKBWBOFUQSPKFDUTKEL • ໨తɾ࢓༷΍࢖͍ํɾલճͱͷࠩ෼͕؆ܿʹॻ͔Ε͍ͯΔ • 'VUVSF
    XPSLΛಡΉͱ͞ΒͳΔల๬͕෼͔Δ • +&1ಉ࢜ͷؔΘΓ͕௫ΊΔ 58
60. ࠷ޙʹҰൠ+BWBϢʔβʔ໨ઢͰʜ • ௥͏ͷ͸େม • ͲΜͲΜ৽͍͠όʔδϣϯ͕΍ͬͯ͘Δ • ϓϨϏϡʔػೳ΋͋ͬͯࠓԿ͕ग़དྷΔͷ͔෼͔Βͳ͍ • ԕ͘ʹ͋Δ໨త΍ҙຯΛ೺Ѳ͢Δͱ͔͑ͬͯ෼͔Γ΍͍͢ • +&1΍ϓϩδΣΫτ͸ϚχΞοΫͳ஌ࣝͩͱࢥ͍ͬͯΔํ΋ɺ ஌Δ͜ͱͰָʹͳΕΔ͔΋ʜʁ ʜͦ͏͸͍ͬͯ΋େมͳͷͰίϛϡχςΟ΋׆༻͠Α͏ʂ🌟 59
61. 5IBOL
    ZPV 60