60分で体験するStream/Lambdaハンズオン

෼Ͱମݧ͢Δ  4USFBN-BNCEB  ϋϯζΦϯ !HJTIJ@ZBNB +BWB%Pד׃׳ֲ劦䌽

HJTIJ@ZBNB w ๭஍ํେֶͰFϥʔχϯάͳͲͷ৘ใγεςϜͷ  ։ൃɾݚڀʹैࣄ w 8JDLFU4BQQPSP +BWB%Pˡ/FX w 8JDLFU6TFS(VJEFͷ຋༁ʹνϟϨϯδத IUUQTHJUIVCDPNXJDLFUTBQQPSPXJDLFU@VTFS@HVJEF@KQ

ϋϯζΦϯͷ֓ཁ +BWBͷϦϦʔε͔Β೥͋·Γ͕ܦա͠ɺ4USFBN "1*΍-BNCEB͕ࣜ։ൃ؀ڥʹಋೖ͞ΕΔࣄྫ΋࣍ୈ ʹ૿͖͍͑ͯͯΔ͜ͱͱࢥ͍·͢ɻ 4USFBN"1*΍-BNEBࣜͷ͘͠Έɾॻ͖ํɾϧʔϧͷ جຊͱɺ͜ΕΒΛ༻͍ͯطଘͷ+BWBίʔυΛͲ͏ม Խͤ͞Δ͜ͱ͕Ͱ͖Δͷ͔ɺମݧͯ͠Έ·͠ΐ͏ɻ

࿅शɾԋशϓϩδΣΫτ https://github.com/java-‐do/20150823_seminar b%PXOMPBE;JQ`Λͯ͠ల։ʢ΋͘͠͸HJUͰDMPOFʣ TUSFBNϑΥϧμΛΠϯϙʔτ &DMJQTFɿ&YJTUJOH.BWFO1SPKFDUʢطଘͷ.BWFOϓϩδΣΫτʣ /FU#FBOTɿϓϩδΣΫτΛ։͘ ࢦࣔʹैͬͯ)BOET0OKBWBΛฤू͠ɺϑΝΠϧΛ࣮ߦ͢Δ ղ౴ྫ͸"OTXFSKBWBʹهࡌ͞Ε͍ͯΔ

4USFBN-BNCEB +BWBʹࡉ͔͍ฒྻॲཧΛಋೖ͢ΔͨΊɺ+BWB͔Βಋ ೖ͞Εͨ"1*΍ه๏ͷ͜ͱ w 4USFBNɿ  ഑ྻɺ-JTUɺ4FUɺ.BQͱ͍ͬͨίϨΫγϣϯతͳ ΦϒδΣΫτ΁ͷॱ࣍ɾฒྻॲཧΛهड़͢Δ"1* w -BNCEBɿ  ಗ໊ͷؔ਺ΦϒδΣΫτΛ࡞ΔͨΊͷؔ਺ܕΠϯ
λʔϑΣʔεͷ࣮૷ʢͱͦͷه๏ʣ

BHFT ͨͱ͑͹ɺ഑ྻΛදࣔ͢Δ ‣ BHFTΛཁૉ਺෼܁Γฦ͢ ‣
JΛཁૉ൪߸ͱͯ͠ɺBHFT͔ΒཁૉΛऔΓग़͢ ‣ औΓग़ͨ͠ཁૉΛදࣔ͢Δ int[] ages = new int[]{22, 10, 19, 38}; for (int i = 0; i < ages.length; i++) { System.out.println(ages[i]); }

BHFT ͨͱ͑͹ɺ഑ྻΛදࣔ͢Δ 4USFBN int[] ages
= new int[]{22, 10, 19, 38}; Arrays.stream(ages) .forEach(n -‐> System.out.println(n)); ‣ BHFTΛTUSFBNʹ͢Δ ‣ TUSFBNͷཁૉOΛ4ZTUFNPVUQSJOUMO O Ͱදࣔ͢Δ

Ⳣ椚ׇׁ׋ְֿהָ  ״׶僇然ח٥知稆ח剅ֽ׷ ‣ BHFTΛཁૉ਺෼܁Γฦ͢ ‣ JΛཁૉ൪߸ͱͯ͠ɺBHFT͔ΒཁૉΛऔΓग़͢ ‣ औΓग़ͨ͠ཁૉΛදࣔ͢Δ ‣
BHFTΛTUSFBNʹ͢Δ ‣ TUSFBNͷཁૉOΛ4ZTUFNPVUQSJOUMO O Ͱදࣔ͢Δ

BHFT ͨͱ͑͹ɺબΜͰදࣔ͢Δ ‣ BHFTΛཁૉ਺෼܁Γฦ͢ ‣ JΛཁૉ൪߸ͱͯ͠ɺBHFT͔ΒཁૉOΛऔΓग़͢
‣ O͕Ҏ্ͷ͚࣌ͩɺԼΛ࣮ߦ͢Δ ‣ OΛදࣔ͢Δ ˞Ҏ্Λදࣔ int[] ages = new int[]{22, 10, 19, 38}; for (int i = 0; i < ages.length; i++) { int n = ages[i]; if (n >= 20) { System.out.println(n); } }

BHFT ͨͱ͑͹ɺબΜͰදࣔ͢Δ 4USFBN ‣ BSHTΛ4USFBNʹ͢Δ
‣ TUSFBNͷཁૉO͕Ҏ্ͷ΋ͷ͚ͩʹϑΟϧλ͢Δ ‣ ࢒ͬͨཁૉOΛදࣔ͢Δ ˞Ҏ্Λදࣔ int[] ages = new int[]{22, 10, 19, 38}; Arrays.stream(ages) .filter(n -‐> n >= 20) // 22, 38ͷΈͷStream͕Ͱ͖Δ .forEach(n -‐> System.out.println(n));

Ⳣ椚ׇׁ׋ְֿהָ  ״׶僇然ח٥知稆ח剅ֽ׷ 㣐✲ז✲זךד䏝 ‣ BHFTΛཁૉ਺෼܁Γฦ͢ ‣ JΛཁૉ൪߸ͱͯ͠ɺBHFT͔ΒཁૉOΛऔΓग़͢ ‣ O͕Ҏ্ͷ͚࣌ͩɺԼΛ࣮ߦ͢Δ
‣ OΛදࣔ͢Δ ‣ BSHTΛ4USFBNʹ͢Δ ‣ TUSFBNͷཁૉO͕Ҏ্ͷ΋ͷ͚ͩʹϑΟϧλ͢Δ ‣ ࢒ͬͨཁૉOΛදࣔ͢Δ

࿅शΛ ΍ͬͯΈ·͠ΐ͏

4USFBNͷߏ଄ int[] ages = new int[]{22, 10, 19, 38};
Arrays.stream(ages) .filter(n -‐> n >= 20) .forEach(n -‐> System.out.println(n)); ˘4USFBNך欰䧭 ˘⚥꟦乼⡲ ˘穄畭乼⡲ ‣ ऴ୺ૢ࡞͕࣮ߦ͞ΕΔͱ͖ʹɺύΠϓϥΠϯͷશ͕࣮ͯߦ͞ΕΔ ‣ ͦΕͧΕʹͲͷΑ͏ͳछྨ͕͋Δͷ͔͸  !IJTJEBNB͞Μͷ  IUUQXXXOFKQBTBIJIJTIJEBNBIPNFUFDIKBWB TUSFBNIUNMI@NFUIPE͕Θ͔Γ΍͍͢ ετϦʔϜɾύΠϓϥΠϯ

BHFT ฒྻॲཧ 4USFBN ˞Ҏ্Λදࣔ int[]
ages = new int[]{22, 10, 19, 38}; Arrays.stream(ages) .parallel() .filter(n -‐> n >= 20) .forEach(n -‐> System.out.println(n)); TUSFBNΛQBSBMMFMTUSFBNʹมԽͤ͞Δ͚ͩͰɺ  ฒྻॲཧʹͳΔ ˞ॱংอূͩͱύϑΥʔϚϯε͸Լ͕Δ

BHFT ཁૉͷೖΕସ͑ 4USFBN NBQɺNBQ5P99ͱ͍͏ϝιουͰɺཁૉΛೖΕସ͑ͨ 4USFBNΛੜ੒͠ɺॲཧΛܧଓ͢Δ
Arrays.stream(ages) .filter(n -‐> n >= 20) // 22, 38ͷΈͷStream͕Ͱ͖Δ .mapToObj(n -‐> Integer.toBinaryString(n)) // 2ਐ਺Խͨ͠Stream͕Ͱ͖Δ .forEach(n -‐> System.out.println(n));

-BNCEBࣜ ɾn -‐> n >= 20 ɾn -‐>
Integer.toBinaryString(n) ɾn -‐> System.out.println(n) 4USFBNͷதʹݱΕͨ ͜ΕΒ͕-BNCEBʢϥϜμʣࣜɻ ϥϜμࣜ͸ɺzࣜzͷ༷ʹॲཧʢؔ਺ʣΛॻ͚Δ ʮؔ਺ΦϒδΣΫτʯ +BWBͰ͸ɺؔ਺ܕΠϯλʔϑΣʔεͷແ໊Ϋϥε͕ݪܕ

ແ໊Ϋϥε ΠϯελϯεԽͷࡍʹ\^Λ͚ͭΔ͜ͱͰɺαϒΫϥε΍Πϯλʔ ϑΣʔεͷ࣮૷ΫϥεͷΦϒδΣΫτΛͦͷ৔Ͱ࡞Δ͜ͱ͕Ͱ͖Δɻ ͜ͷαϒΫϥεʹ͸ɺΫϥε໊͕ͳ͍ɻ ͜ͷख๏ʢͱɺ࡞ΒΕͨΫϥεʣΛແ໊Ϋϥεͱ͍͏ɻ public class GamePlayer extends AbstractPlayer
{ // AbstractPlayerͷαϒΫϥε // ͜ͷαϒΫϥεʹ͸(BNF1MBZFSͱ͍͏Ϋϥε໊લ͕͋Δ } AbstractPlayer player = new AbstractPlayer() { // ͜ͷΦϒδΣΫτ͸ɺAbstractPlayerͷαϒΫϥεͷΦϒδΣΫτͱͳΔ // αϒΫϥεʹ͸Ϋϥε໊͕ଘࡏ͠ͳ͍ͷͰɺແ໊Ϋϥεͱݺ͹ΕΔ }; ˣ௨ৗͷαϒΫϥε ˢແ໊Ϋϥε

ؔ਺ܕΠϯλʔϑΣʔε 4USFBNװ؎كٝزⳢ椚זוד遤׻׸׷Ⳣ椚ꟼ侧׾㹀纏דֹ׷؎ٝة٦ؿؑ٦أ 4VQQMJFS⦼ך欰䧭䒷侧ז׃ 鵤⦼֮׶  1SFEJDBUF勴⟝ⴻ㹀䒷侧א 鵤⦼כCPPMFBO  'VODUJPO⦼ך㢌䳔䒷侧א 鵤⦼֮׶  $POTVNFS⦼ךⳢ椚䒷侧א
鵤⦼ז׃  3VOOBCMFⳢ椚㹋遤䒷侧ז׃ 鵤⦼ז׃ זוך垥彊ꟼ侧㘗؎ٝة٦ؿؑ٦أָ֮׷  KBWBVUJMGVODUJPO

int[] ages = new int[]{22, 10, 19, 38}; IntConsumer
consumer = new IntConsumer() { // $POTVNFSͷແ໊Ϋϥε @Override public void accept(int n) { System.out.println(n); } }; Arrays.stream(ages) .forEach(consumer);ɹ ྫɿ഑ྻΛදࣔ͢Δऴ୺ૢ࡞ͷ $POTVNFSͷແ໊Ϋϥε

consumer = new IntConsumer() { // $POTVNFSͷແ໊Ϋϥε @Override public void accept(int n) { System.out.println(n); } }; Arrays.stream(ages) .forEach(consumer);ɹ ແ໊Ϋϥε͔ΒϥϜμࣜ΁

consumer = n -‐> System.out.println(n); Arrays.stream(ages) .forEach(consumer);ɹ ϥϜμࣜ

consumer = n -‐> System.out.println(n); Arrays.stream(ages) .forEach(n -‐> System.out.println(n));ɹ Ҿ਺ʹ௚઀౉͢

Ξϩʔԋࢉࢠͷࠨล͕ෳ਺ߦ ʹͳΔͱ͖͸\^ͰғΉ int[] ages = new int[]{22, 10, 19, 38};
Arrays.stream(ages) .forEach(n -‐> { String s = n + "ࡀ"; System.out.println(s); });

࿅श ԋशʙΛ ΍ͬͯΈ·͠ΐ͏

List<String> choiced = profiles.stream() .filter(p -‐> p.isFamale())
.filter(p -‐> p.isAdult()) .map(p -‐> p.getName()) .forEach(i -‐> System.out.println(i)); List<String> choiced = profiles.stream() .filter(Profile::isFamale) .filter(Profile::isAdult) .map(Profile::getName) .forEach(System.out::println); ϝιουࢀর ϥϜμࣜͷ෦෼Λ ΦϒδΣΫτϝιου໊ Ϋϥεϝιου໊ ʹॻ͖׵͑ΒΕΔʢҾ਺΋ਪଌ͞ΕΔʣ

෭࡞༻͸ʢۃྗʣආ͚Δ StringJoiner joiner = new StringJoiner(",", "Profile{", "}"); Stream.of(name,
sex.toString(), age.toString(), state, policy) .forEach(joiner::add); StringJoiner joiner = new StringJoiner(",", "Profile{", "}"); Stream.of(name, sex.toString(), age.toString(), state, policy) .parallel() .forEach(joiner::add); KPJOFSʹมԽʢ෭࡞༻ʣΛ༩͑Δ4USFBN ্ʢॱ࣍ॲཧʣͱԼʢฒྻॲཧʣͰ݁Ռ͕ҟͳΔʂ ΍ΉΛ͑ͳ͍৔߹΋͋Δ͕ɺ෭࡞༻ͷ͋Δॲཧ͸ۃྗ͚͞Δ͜ͱͰɺ Τϥʔͷ๷ࢭ΍ฒྻԽΛ͠΍͘͢ͳΔ ˞ͳ͓ɺϥϜμࣜͷ໊Ͱݺͼग़͞ΕΔม਺͸҉໧తʹpOBMͱͳΔ  ɹʢ্ͷྫͰ͸ɺKPJOFS͕pOBMͱͯ͠ѻΘΕΔʣ

·ͱΊ

·ͱΊ Stream: ίϨΫγϣϯతͳΦϒδΣΫτ΁ͷॱ࣍ɾฒྻ ॲཧΛύΠϓϥΠϯͰهड़Ͱ͖Δ Lambda: ؔ਺ܕΠϯλʔϑΣʔεͷ࣮૷ʢStream಺Ͱ  ॲཧ͍ͤͨ͞಺༰ͳͲʣΛࣜ΍ϝιουࢀরͰॻ͚Δ Stream
API / LambdaΛ࢖͏͜ͱͰɺforจΛ࢖͏ॲཧ  ΛΑΓ໌֬ʹɾ؆ૉʹॻ͚Δ streamΛparallelԽ͢Δ͚ͩͰฒྻॲཧΛߦΘͤΔ͜ͱ ͕Ͱ͖ΔΑ͏ʹͳΔʢ෭࡞༻ͷ༗ແʹ஫ҙʣ

8JDLFU΋কདྷతʹ͸ʜ .BSUJKO%BTIPSTU "QBDIF8JDLFUZFBSTCFZPOE

ࢀߟจݙ ɾ+BWBʹΑΔؔ਺ܕϓϩάϥϛϯάʢ*4#/ʣ ɾ+BWBϓϩάϥϚʔͳΒशಘ͓͖͍ͯͨ͠+BWB4&࣮ફϓϩάϥϛϯά ʢ*4#/ʣ

ࢀߟจݙ ɾ͖ͭͶ͞ΜͱֶͿ-BNCEBࣜ4USFBN"1*ϋϯζΦϯ IUUQXXXTMJEFTIBSFOFUCJUUFS@GPYIBOETPO  IUUQTCJUCVDLFUPSHCJUUFS@GPYMBNCEBHJU ɾͻͩ͠·ͷϗʔϜϖʔδɿ+BWB4USFBN IUUQXXXOFKQBTBIJIJTIJEBNBIPNFUFDIKBWBTUSFBNIUNM ɾ+BWBͷTUSFBNΛ࢖͍͜ͳ͢ɿ͖ͩ͠ͷ͸ͯͳ IUUQEIBUFOBOFKQOPXPLBZ ɾ+BWBͷ4USFBNͰֶͿ஗Ԇॲཧ࣮૷ύλʔϯ IUUQXXXTMJEFTIBSFOFUNJLFOFDLKBWBTUSFBN
ɾࣾ಺+BWBษڧձϥϜμࣜͱετϦʔϜ"1* IUUQXXXTMJEFTIBSFOFU[PFUSPQFKBWBMBNCEBBOETUSFBN ɾ"QBDIF8JDLFUZFBSTCFZPOE IUUQXXXTMJEFTIBSFOFUEBTIPSTUXJDLFUZFBSTBOECFZPOE

60分で体験するStream/Lambdaハンズオン

60分で体験するStream/Lambdaハンズオン

Hiroto YAMAKAWA

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෼Ͱମݧ͢Δ  4USFBN-BNCEB  ϋϯζΦϯ !HJTIJ@ZBNB +BWB%Pד׃׳ֲ劦䌽

HJTIJ@ZBNB w ๭஍ํେֶͰFϥʔχϯάͳͲͷ৘ใγεςϜͷ  ։ൃɾݚڀʹैࣄ w 8JDLFU4BQQPSP +BWB%Pˡ/FX w 8JDLFU6TFS(VJEFͷ຋༁ʹνϟϨϯδத IUUQTHJUIVCDPNXJDLFUTBQQPSPXJDLFU@VTFS@HVJEF@KQ

ϋϯζΦϯͷ֓ཁ +BWBͷϦϦʔε͔Β೥͋·Γ͕ܦա͠ɺ4USFBN "1΍-BNCEB͕ࣜ։ൃ؀ڥʹಋೖ͞ΕΔࣄྫ΋࣍ୈ ʹ૿͖͍͑ͯͯΔ͜ͱͱࢥ͍·͢ɻ 4USFBN"1΍-BNEBࣜͷ͘͠Έɾॻ͖ํɾϧʔϧͷ جຊͱɺ͜ΕΒΛ༻͍ͯطଘͷ+BWBίʔυΛͲ͏ม Խͤ͞Δ͜ͱ͕Ͱ͖Δͷ͔ɺମݧͯ͠Έ·͠ΐ͏ɻ

4USFBN-BNCEB +BWBʹࡉ͔͍ฒྻॲཧΛಋೖ͢ΔͨΊɺ+BWB͔Βಋ ೖ͞Εͨ"1΍ه๏ͷ͜ͱ w 4USFBNɿ  ഑ྻɺ-JTUɺ4FUɺ.BQͱ͍ͬͨίϨΫγϣϯతͳ ΦϒδΣΫτ΁ͷॱ࣍ɾฒྻॲཧΛهड़͢Δ"1 w -BNCEBɿ  ಗ໊ͷؔ਺ΦϒδΣΫτΛ࡞ΔͨΊͷؔ਺ܕΠϯ

BHFT ͨͱ͑͹ɺ഑ྻΛදࣔ͢Δ ‣ BHFTΛཁૉ਺෼܁Γฦ͢ ‣

BHFT ͨͱ͑͹ɺ഑ྻΛදࣔ͢Δ 4USFBN int[] ages

Ⳣ椚ׇׁ׋ְֿהָ  ״׶僇然ח٥知稆ח剅ֽ׷ ‣ BHFTΛཁૉ਺෼܁Γฦ͢ ‣ JΛཁૉ൪߸ͱͯ͠ɺBHFT͔ΒཁૉΛऔΓग़͢ ‣ औΓग़ͨ͠ཁૉΛදࣔ͢Δ ‣

BHFT ͨͱ͑͹ɺબΜͰදࣔ͢Δ ‣ BHFTΛཁૉ਺෼܁Γฦ͢ ‣ JΛཁૉ൪߸ͱͯ͠ɺBHFT͔ΒཁૉOΛऔΓग़͢

BHFT ͨͱ͑͹ɺબΜͰදࣔ͢Δ 4USFBN ‣ BSHTΛ4USFBNʹ͢Δ

Ⳣ椚ׇׁ׋ְֿהָ  ״׶僇然ח٥知稆ח剅ֽ׷ 㣐✲ז✲זךד䏝 ‣ BHFTΛཁૉ਺෼܁Γฦ͢ ‣ JΛཁૉ൪߸ͱͯ͠ɺBHFT͔ΒཁૉOΛऔΓग़͢ ‣ O͕Ҏ্ͷ͚࣌ͩɺԼΛ࣮ߦ͢Δ

࿅शΛ ΍ͬͯΈ·͠ΐ͏

4USFBNͷߏ଄ int[] ages = new int[]{22, 10, 19, 38};

BHFT ฒྻॲཧ 4USFBN ˞Ҏ্Λදࣔ int[]

BHFT ཁૉͷೖΕସ͑ 4USFBN NBQɺNBQ5P99ͱ͍͏ϝιουͰɺཁૉΛೖΕସ͑ͨ 4USFBNΛੜ੒͠ɺॲཧΛܧଓ͢Δ

-BNCEBࣜ ɾn -‐> n >= 20 ɾn -‐>

ແ໊Ϋϥε ΠϯελϯεԽͷࡍʹ\^Λ͚ͭΔ͜ͱͰɺαϒΫϥε΍Πϯλʔ ϑΣʔεͷ࣮૷ΫϥεͷΦϒδΣΫτΛͦͷ৔Ͱ࡞Δ͜ͱ͕Ͱ͖Δɻ ͜ͷαϒΫϥεʹ͸ɺΫϥε໊͕ͳ͍ɻ ͜ͷख๏ʢͱɺ࡞ΒΕͨΫϥεʣΛແ໊Ϋϥεͱ͍͏ɻ public class GamePlayer extends AbstractPlayer

ؔ਺ܕΠϯλʔϑΣʔε 4USFBNװ؎كٝزⳢ椚זוד遤׻׸׷Ⳣ椚ꟼ侧׾㹀纏דֹ׷؎ٝة٦ؿؑ٦أ 4VQQMJFS⦼ך欰䧭䒷侧ז׃ 鵤⦼֮׶  1SFEJDBUF勴⟝ⴻ㹀䒷侧א 鵤⦼כCPPMFBO  'VODUJPO⦼ך㢌䳔䒷侧א 鵤⦼֮׶  $POTVNFS⦼ךⳢ椚䒷侧א

int[] ages = new int[]{22, 10, 19, 38}; IntConsumer

int[] ages = new int[]{22, 10, 19, 38}; IntConsumer

int[] ages = new int[]{22, 10, 19, 38}; IntConsumer

int[] ages = new int[]{22, 10, 19, 38}; IntConsumer

Ξϩʔԋࢉࢠͷࠨล͕ෳ਺ߦ ʹͳΔͱ͖͸\^ͰғΉ int[] ages = new int[]{22, 10, 19, 38};

࿅श ԋशʙΛ ΍ͬͯΈ·͠ΐ͏

List<String> choiced = profiles.stream() .filter(p -‐> p.isFamale())

෭࡞༻͸ʢۃྗʣආ͚Δ StringJoiner joiner = new StringJoiner(",", "Profile{", "}"); Stream.of(name,

·ͱΊ

·ͱΊ Stream: ίϨΫγϣϯతͳΦϒδΣΫτ΁ͷॱ࣍ɾฒྻ ॲཧΛύΠϓϥΠϯͰهड़Ͱ͖Δ Lambda: ؔ਺ܕΠϯλʔϑΣʔεͷ࣮૷ʢStream಺Ͱ  ॲཧ͍ͤͨ͞಺༰ͳͲʣΛࣜ΍ϝιουࢀরͰॻ͚Δ Stream

8JDLFU΋কདྷతʹ͸ʜ .BSUJKO%BTIPSTU "QBDIF8JDLFUZFBSTCFZPOE

ࢀߟจݙ ɾ+BWBʹΑΔؔ਺ܕϓϩάϥϛϯάʢ4#/ʣ ɾ+BWBϓϩάϥϚʔͳΒशಘ͓͖͍ͯͨ͠+BWB4&࣮ફϓϩάϥϛϯά ʢ4#/ʣ