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Lightweight-Stream-API ͷ͋ΔAndroidΞϓϦ։ൃ ୈ1ճελʔτΞοϓAndroidษڧձ

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About Me Shinobu Okano @operandoOS Mercari, Inc. Souzoh, Inc.

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Lightweight-Stream-API? "Stream API from Java 8 rewritten on iterators for Java 7 and below." https://github.com/aNNiMON/Lightweight-Stream-API

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Lightweight-Stream-API? AndroidͰ΋࢖͑Δʂʂ

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Lightweight-Stream-API? Ϡλʔ

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Lightweight-Stream-API Includes • Functional interfaces • Stream/IntStream • Optional class • Exceptional class • Objects from Java 7

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Stream͚ͩ͡Όͳ͍Μ΍Ͱʔʂʂ Lightweight-Stream-API Includes

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ͪͳΈʹ... • Lightweight-Stream-API໊ͬͯલ͕௕͍... • LSAͬͯ༁ͬ͢Ά͍ • READMEʹLSAͬͯهड़͕͋ͬͨ • ࢿྉͳ͍ͰLSAͱॻ͍ͯ͋Δͷ͸
 Lightweight-Stream-APIͱ͍͏ҙຯͰ͢

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Stream

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Stream? Java 8Ͱಋೖ͞ΕͨAPI

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Stream? "A sequence of elements supporting sequential and parallel aggregate operations."

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Stream(ਖ਼͘͠͸ͳ͍͚Ͳࡶʹ...) ܁Γฦ͠ॲཧͷfor΍whileΛStreamʹͯ͠ ύΠϓϥΠϯతʹॲཧ͢Δ

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Lightweight-Stream-API • "without parallel processing but with a variety of additional methods and with custom operators" • parallel͸ఏڙ͞Ε͍ͯͳ͍

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Lightweight-Stream-API ≠ Java 8 Stream • ΠίʔϧͰ͸ͳ͍ • Java 8 Stream APIͷΑ͏ͳΠϯλʔϑΣΠε ΋ͬͨ΋ͷ

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StreamͷྲྀΕ • Streamͷੜ੒ • தؒૢ࡞ (map,filter,etc.) • ͋ΔετϦʔϜΛผͷετϦʔϜʹม׵͢Δૢ࡞ • ऴ୺ૢ࡞ (forEach,count,collect,etc.) • ݁Ռ·ͨ͸෭࡞༻Λੜ੒͢Δૢ࡞

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Java 8 Stream • είΞͷList͔Β30఺Ҏ্ͷ΋ͷΛදࣔ͢Δ • Java 8ͷCollectionʹStreamʹม׵͢Δϝιου͕͋Δ List scores = Arrays.asList(100, 30, 35, 20); scores.stream() // Streamͷੜ੒ .filter(score -> score >= 30) // தؒૢ࡞ .forEach(System.out::println); // ऴ୺ૢ࡞

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for • είΞͷList͔Β30఺Ҏ্ͷ΋ͷΛදࣔ͢Δ for (Integer score : scores) { if (score >= 30) { System.out.println(score); } }

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Java 8 Parallel Stream • parallelStream()Ͱฒྻॲཧ • ฒྻͰॲཧ͢ΔͷͰ݁Ռͷॱ൪͸มΘΔՄೳੑ͕͋Δ List scores = Arrays.asList(100, 30, 35, 20); scores.parallelStream() .filter(score -> score >= 30) .forEach(System.out::println);

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Lightweight-Stream-API • είΞͷList͔Β30఺Ҏ্ͷ΋ͷΛදࣔ͢Δ • Stream.ofͰStreamΛ࡞Δ List scores = Arrays.asList(100, 30, 35, 20); Stream.of(scores) // Streamͷੜ੒ .filter(score -> score >= 30) // தؒૢ࡞ .forEach(System.out::println); // ऴ୺ૢ࡞

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ग़ྗ͡Όͳͯ͘Listʹ͍ͨ͠ʂ(Lightweight-Stream-API) • ऴ୺ૢ࡞Λcollectʹ͢Δ͚ͩͳͷͰ؆୯ʂ List scores = Arrays.asList(100, 30, 35, 20); List filteredScores = Stream.of(scores) .filter(score -> score >= 30) .collect(Collectors.toCollection(ArrayList::new));

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தؒૢ࡞ɺऴ୺ૢ࡞ͷϝιου͸৭ʑ͋Δ! • શ෦આ໌Ͱ͖ͳ͍ͷͰɺjavadocͱ͔Έͯࢼͯ͠Ͷʂ • େମ΄͍͠ͱࢥ͏ػೳ͸ἧͬͯΔ͸ͣ • Stream - Lightweight-Stream-API javadoc • http://static.javadoc.io/com.annimon/stream/ 1.1.3/com/annimon/stream/Stream.html

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Lightweight-Stream-API • AndroidͰJava 8ͷStreamͬΆ͍΋ͷ͕࢖͑Δʂ • தؒૢ࡞ͱऴ୺ૢ࡞͸ಉ͡Ͱॻ͚Δ • ྲྀΕΔΑ͏ʹॲཧΛॻ͚ΔͷͰؾ͍͍࣋ͪ! • Javaྗ UP • Java 9ͰStreamʹ௥Ճ͞ΕΔfunction΋࢖͑Δ! • good-bye for??

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Optional

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Optional? "A container object which may or may not contain a non-null value."

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Optional?(ࡶ) ஋Λϥοϓͯ͠null͔΋͠Εͳ͍ ͜ͱΛදݱ͢ΔΫϥε

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good-bye NullPointerException? NO

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Optional - Java 8 Optional optional = OptionalΛฦ͢ϝιου(); // nullͰͳ͚Ε͹දࣔ͞ΕΔ optional.ifPresent(System.out::println);

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Optional - Lightweight-Stream-API Optional optional = OptionalΛฦ͢ϝιου(); // nullͰͳ͚Ε͹දࣔ͞ΕΔ optional.ifPresent(System.out::println);

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ಉ͡΍☺

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Optional + Android • Android SDKͷAPIͬͯࢥͬͨҎ্ʹnullΛฦ͢΋ͷ͕ଟ͍ • υΩϡϝϯτಡΜͰʮ͑?nullฦΔͷ?ʯͱ஌Δ΋ͷ΋౓ʑ • FragmentͶʔgetContextͱ͔getActivityͱ͔… • ίʔυϨϏϡʔͰ͔ͭͬͭΕͨ͘ͳ͍… • Fragment#getResources΋mHost͕nullͩͱ IllegalStateException

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Fragment#getContext() "Return the Context this fragment is currently associated with." https://developer.android.com/reference/android/support/v4/app/Fragment.html#getContext()

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Fragment#getContext() • nullฦΔ΍Μ public Context getContext() { return mHost == null ? null : mHost.getContext(); }

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Fragment + Optional public static Optional getOptionalContext(Fragment fragment) { if (fragment.isDetached()) { return Optional.empty(); } return Optional.ofNullable(fragment.getContext()); } // ҆શ! FragmentUtil.getOptionalContext(this) .ifPresent(context -> { Toast.makeText(context, "Optional", Toast.LENGTH_SHORT).show(); });

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Fragment + Optional public static Optional getOptionalFragmentActivity(Fragment fragment) { if (fragment.isDetached()) { return Optional.empty(); } return Optional.ofNullable(fragment.getActivity()); } // menuͷߋ৽ // ҆શ! FragmentUtil.getOptionalFragmentActivity(this) .ifPresent(FragmentActivity::supportInvalidateOptionsMenu);

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Fragment + Optional public static Optional getArguments(Fragment fragment) { return Optional.ofNullable(fragment.getArguments()); } // ҆શ! FragmentUtil.getArguments(this) .ifPresent(bundle -> { // bundle͔Β஋ΛऔΓग़͢ });

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ෳ਺ͷOptionalΛѻ͏ • Optional AͱOptional Bͷ྆ํ͕nullͰͳ͚Ε͹...Έ͍ͨͳύλʔϯ • ͦ΋ͦ΋͜ΕͰਖ਼͍͠ͷ͔Θ͔Βͳ͍... Optional optionalFragmentActivity = FragmentUtil.getOptionalFragmentActivity(this); Optional titleOptional = titleOptional(); optionalFragmentActivity.ifPresent(fragmentActivity -> { titleOptional.ifPresent(title -> { fragmentActivity.setTitle(title); }); });

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ෳ਺ͷOptionalΛѻ͏ • 2ͭͷOptionalʹ஋͕ೖ͍ͬͯΕ͹
 TupleΛOptionalͰϥοϓͯ͠ฦ͢ • ͜ΕͳΒͲ͏ͩ

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ෳ਺ͷOptionalΛѻ͏ public static Optional> flatMapPair(Optional a, Optional b) { if (a.isPresent() && b.isPresent()) { // 2ͭͷOptionalʹ஋͕ೖ͍ͬͯΕ͹TupleΛOptionalͰϥοϓͯ͠ฦ͢ return Optional.ofNullable(Pair.create(a.get(), b.get())); } else { // ͦ͏Ͱͳ͍ͳΒempty return Optional.empty(); } } OptionalUtil.flatMapPair(optionalFragmentActivity,titleOptional) .ifPresent(pair -> { pair.getFirst()setTitle(pair.getSecond()); });

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ෳ਺ͷOptionalΛѻ͏ public static Optional> flatMapTriplet(Optional a, Optional b, Optional c) { if (a.isPresent() && b.isPresent() && c.isPresent()) { return Optional.ofNullable( Triplet.create(a.get(), b.get(), c.get())); } else { return Optional.empty(); } }

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Ͱ΋ JavaʹTupleͳ͍΍Μ...

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Guild • • Simple java tuples. • https://github.com/operando/Guild

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LSAͷOptionalʹ͔͠ͳ͍ศརͳϝιου • Optional.stream() • Optional͔ΒStreamʹม׵Ͱ͖Δ • ଞʹ΋͍͔ͭ͋͘Δ… Optional.ofNullable(integers) .stream() .forEach(System.out::println);

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Java 8Ͱಉ͜͡ͱΛ͢Δͱ • Ұखؒඞཁ Optional.ofNullable(integers) .map(integers1 -> integers1.stream()) .orElse(Stream.empty()) .forEach(System.out::println);

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Optionalʹ΋தؒૢ࡞ɺऴ୺ૢ࡞తͳͷ͕͋Δ • தؒૢ࡞?తͳͷ • map,flagMap,filter,etc… • ऴ୺ૢ࡞?తͳͷ • ifPresent,orElse,etc… • Optional javadoc - Lightweight-Stream-API • http://static.javadoc.io/com.annimon/stream/1.1.3/com/ annimon/stream/Optional.html

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Optional • AndroidͰJava 8ͷOptionalͱಉ͡Α͏ͳ΋ͷ͕࢖͑Δ • Javaྗ UP • ifͰnullνΣοΫ͢ΔΑΓࣗવͳײ͡ͰϓϩάϥϜ͕ॻ͚Δ • null͕ͳ͘ͳΔΘ͚Ͱ͸ͳ͍ • ѻ͍͕೉͍͜͠ͱ΋͋Δ • Optionalͷϥοϓͯ͠Δ஋͕nullͩͬͨ࣌ͷॲཧΛ๨ΕΔͱ͔...

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Objects

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Objects΋͍͍ͧʂ • Java 7͔Β௥Ճ͞ΕͨAPI • AndroidͰ͸minSdkVersion 19Ҏ্͡Όͳ͍ ͱJava 7ͷAPI͸࢖͑ͳ͍͸ͣ

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Objects΋͍͍ͧʂ • ̎ͭͷจࣈྻΛൺֱ͍ͨ͠ String s1 = Stringฦ͢ϝιου(); String s2 = Stringฦ͢ϝιου(); // s1͸null͔΋͠Εͳ͍... s1.equals(s2); // Objects - Lightweight-Stream-API // ͲͪΒ͔͕nullͰ΋҆શ! Objects.equals(s1,s2);

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Andorid N minSdkVersion 24 • Java 8ͷAPI͕͍͔ͭ͘ೖͬͯΔ • StreamͱOptional͸ೖͬͯΔ • ଞʹ΋͍͔ͭ͘… • Lightweight-Stream-API࢖Θͳͯ͘΋Α͍ • minSdkVersion 24...Կ೥ઌ?

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Android-Java-8-Stream-Example • Lightweight-Stream-APIͷ࡞ऀ͕AndroidͰ Java 8ͬΆ͘ॻ͘αϯϓϧΛॻ͍ͯΔ • https://github.com/aNNiMON/Android- Java-8-Stream-Example

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·ͱΊ • Lightweight-Stream-APIΛ࢖͑͹
 AndroidͰ΋StreamͬΆ͍΋ͷͱOptional͕࢖͑Δ • Javaྗ UPʹͭͳ͕Δ • Android։ൃͷJavaͩͱJava 6,7Ͱٕज़͕ࢭ·ͬͯ͠·͏Մೳੑ΋… • ๻ͱҰॹʹ։ൃ͢Δਓʹ͸Javaͷྗ΋͚ͭͯ΄͍͠ • Java 9΋དྷ೥ग़ΔͷͰJavaࣗମʹؔ৺Λʂ

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Links • Lightweight-Stream-API version 1.1.3 javadoc • http://static.javadoc.io/com.annimon/stream/1.1.3/overview-summary.html • Stream - Java 8 • https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html • Java 8 Stream Tutorial • http://winterbe.com/posts/2014/07/31/java8-stream-tutorial-examples/ • Optional - Java 8 • https://docs.oracle.com/javase/8/docs/api/java/util/Optional.html • OptionalͷऔΓѻ͍͔ͨ • http://irof.hateblo.jp/entry/2015/05/05/071450

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Thanks