{"id":9947,"date":"2016-01-04T10:00:26","date_gmt":"2016-01-04T01:00:26","guid":{"rendered":"http:\/\/www.techscore.com\/blog\/?p=9947"},"modified":"2018-11-14T16:33:46","modified_gmt":"2018-11-14T07:33:46","slug":"java8-stream-%e3%81%a7%e3%81%8a%e6%89%8b%e8%bb%bd%e3%81%ab%e4%b8%a6%e5%88%97%e5%87%a6%e7%90%86%e3%81%97%e3%82%88%e3%81%86","status":"publish","type":"post","link":"https:\/\/www.techscore.com\/blog\/2016\/01\/04\/java8-stream-%e3%81%a7%e3%81%8a%e6%89%8b%e8%bb%bd%e3%81%ab%e4%b8%a6%e5%88%97%e5%87%a6%e7%90%86%e3%81%97%e3%82%88%e3%81%86\/","title":{"rendered":"Java8 Stream \u3067\u304a\u624b\u8efd\u306b\u4e26\u5217\u51e6\u7406\u3057\u3088\u3046"},"content":{"rendered":"

\u3053\u3093\u306b\u3061\u306f\u3001\u5bfa\u5ca1\u3067\u3059\u3002
\n\u4eca\u65e5\u306fJava8\u306eStream\u3092\u4f7f\u3063\u305f\u304a\u624b\u8efd\u306a\u4e26\u5217\u51e6\u7406\u3068\u3001\u3061\u3087\u3063\u3068\u3057\u305f\u6ce8\u610f\u70b9\u3092\u3054\u7d39\u4ecb\u3057\u307e\u3059\u3002<\/p>\n

Stream#parallel() \u3067\u4e26\u5217\u51e6\u7406<\/h2>\n

Java8 \u306e Stream#parallel()<\/a> \u30e1\u30bd\u30c3\u30c9\u3092\u4f7f\u3046\u3068\u3001\u7c21\u5358\u306b\u4e26\u5217\u51e6\u7406\u3092\u884c\u3046\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n

\r\nIntStream.rangeClosed(1, 10).parallel().forEach(System.out::println);\r\n\/\/ \u30de\u30eb\u30c1\u30b9\u30ec\u30c3\u30c9\u306a\u306e\u3067\u9806\u4e0d\u540c\u3067\u51fa\u529b\u3055\u308c\u308b\r\n7\r\n6\r\n1\r\n2\r\n8\r\n10\r\n3\r\n5\r\n4\r\n9\r\n<\/pre>\n
<\/p>\n
Stream#parallel() \u306f\u8981\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5<\/h2>\n
Stream#parallel() \u3067\u4e26\u5217\u5316\u3055\u308c\u305f\u30b9\u30c8\u30ea\u30fc\u30e0\u306f\u30de\u30eb\u30c1\u30b9\u30ec\u30c3\u30c9\u3067\u51e6\u7406\u3055\u308c\u308b\u305f\u3081\u3001map \u3084 filter \u306a\u3069\u306e\u4e2d\u9593\u64cd\u4f5c\u3001forEach \u306a\u3069\u306e\u7d42\u7aef\u64cd\u4f5c\u304c\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5\u3067\u306f\u306a\u3044\u5834\u5408\u306b\u554f\u984c\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n
\r\npublic static void main(String[] a) throws Exception {\r\n    Set set1 = new ConcurrentSkipListSet<>();\r\n    digestStream().parallel().map(String::new).forEach(set1::add);   \r\n}\r\n\r\n\/\/ 1\uff5e10000\u307e\u3067\u306e\u6570\u5b57\u6587\u5b57\u5217\u306eSHA-1\u30cf\u30c3\u30b7\u30e5\u5024\u306eStream\u3092\u8fd4\u3059\u3002\r\npublic static Stream digestStream() throws NoSuchAlgorithmException{\r\n    \/\/ \u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u7a3c\u3050\u305f\u3081\u3001MessageDigest\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u3092\u4f7f\u3044\u56de\u3059\u3002\r\n    MessageDigest md = MessageDigest.getInstance(\"SHA-1\");\r\n    \/\/ MessageDigest#digest\u306f\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5\u3067\u306f\u306a\u3044\u306e\u3067\u4e26\u5217\u5b9f\u884c\u3055\u308c\u308b\u3068\u307e\u305a\u3044\u3002\r\n    return IntStream.rangeClosed(1, 10000).mapToObj(i -> String.valueOf(i).getBytes()).map(i -> md.digest(i));\r\n}\r\n<\/pre>\n
\r\nException in thread \"main\" java.lang.ArrayIndexOutOfBoundsException\r\n\tat java.lang.System.arraycopy(Native Method)\r\n\tat sun.security.provider.DigestBase.engineUpdate(DigestBase.java:114)\r\n\tat sun.security.provider.SHA.implDigest(SHA.java:94)\r\n\tat sun.security.provider.DigestBase.engineDigest(DigestBase.java:181)\r\n\tat sun.security.provider.DigestBase.engineDigest(DigestBase.java:160)\r\n\tat java.security.MessageDigest$Delegate.engineDigest(MessageDigest.java:588)\r\n\tat java.security.MessageDigest.digest(MessageDigest.java:365)\r\n\tat com.techscore.Sample.lambda$1(Sample.java:28)\r\n\tat com.techscore.Sample$$Lambda$2\/1406718218.apply(Unknown Source)\r\n\tat java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)\r\n\tat java.util.stream.IntPipeline$4$1.accept(IntPipeline.java:250)\r\n\tat java.util.stream.Streams$RangeIntSpliterator.forEachRemaining(Streams.java:110)\r\n\tat java.util.Spliterator$OfInt.forEachRemaining(Spliterator.java:693)\r\n\tat java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)\r\n\tat java.util.stream.ForEachOps$ForEachTask.compute(ForEachOps.java:291)\r\n\tat java.util.concurrent.CountedCompleter.exec(CountedCompleter.java:731)\r\n\tat java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)\r\n\tat java.util.concurrent.ForkJoinTask.doInvoke(ForkJoinTask.java:401)\r\n\tat java.util.concurrent.ForkJoinTask.invoke(ForkJoinTask.java:734)\r\n\tat java.util.stream.ForEachOps$ForEachOp.evaluateParallel(ForEachOps.java:160)\r\n\tat java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateParallel(ForEachOps.java:174)\r\n\tat java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:233)\r\n\tat java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)\r\n<\/pre>\n
<\/p>\n
Iterator\u3067\u3082\u4e26\u5217\u51e6\u7406<\/h2>\n
Stream#parallel() \u3092\u5229\u7528\u3057\u3066\u3001Iterator \u306b\u5bfe\u3057\u3066\u3082\u4e26\u5217\u51e6\u7406\u3092\u884c\u3048\u307e\u3059\u3002
\n\u30b3\u30ec\u30af\u30b7\u30e7\u30f3\u306f Collection#stream()<\/a> \u3092\u4f7f\u3063\u3066\u7c21\u5358\u306b Stream \u306b\u5909\u63db\u3067\u304d\u307e\u3059\u304c\u3001Iterator \u306e\u5834\u5408\u306f\u3061\u3087\u3063\u3068\u624b\u9806\u304c\u8907\u96d1\u3067\u3059\u3002
\nIterator \u3092\u4e00\u65e6\u3001Spliterator\u3001\u3042\u308b\u3044\u306f Iterable \u306a\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u306b\u5909\u63db\u3057\u3001StreamSupport#stream()<\/a> \u306e\u7b2c\u4e00\u5f15\u6570\u306b\u6e21\u3059\u3053\u3068\u3067 Stream \u306b\u5909\u63db\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n
\r\nIterator iterator = Arrays.asList(1,2,3).iterator();\r\n\r\nStream stream= StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED), false);\r\n      \r\n\/\/ \u3053\u3063\u3061\u3067\u3082OK\r\n\/\/ Iterable iterable = () -> iterator;\r\n\/\/ Stream stream= StreamSupport.stream(iterable.spliterator(), false);\r\n<\/pre>\n
Stream\u306b\u3055\u3048\u306a\u3063\u3066\u3057\u307e\u3048\u3070\u3001\u3042\u3068\u306fparallel\u3092\u547c\u3076\u3060\u3051\u3067\u3059\u306d\u3002<\/p>\n
\r\nstream.parallel().forEach(System.out::println);\r\n<\/pre>\n
Stream \u51e6\u7406\u6642\u306e\u52b9\u7387\u3092\u4e0a\u3052\u308b\u305f\u3081\u306b\u3001\u53ef\u80fd\u3067\u3042\u308c\u3070 Spliterators.spliterator()<\/a> \u306b\u3088\u308a\u30b5\u30a4\u30ba\u6307\u5b9a\u3092\u884c\u3063\u305f\u307b\u3046\u304c\u826f\u3044\u3067\u3057\u3087\u3046\u3002
\n\u307e\u305f\u3001parallel \u3092\u547c\u3073\u3060\u3055\u305a\u3068\u3082\u3001StreamSupport#stream() \u306e\u7b2c\u4e8c\u5f15\u6570\u306btrue\u3092\u6e21\u3059\u3060\u3051\u3067\u4e26\u5217\u5316\u53ef\u80fd\u306a Stream \u3092\u4f5c\u6210\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n
\r\nList list = Arrays.asList(1,2,3);\r\nIterator iterator = list.iterator();\r\nStream stream = StreamSupport.stream(Spliterators.spliterator(iterator, list.size(), 0), false);\r\n<\/pre>\n
<\/p>\n
\u3042\u308c\uff1f Iterator \u3063\u3066\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5\u3058\u3083\u306a\u3044\u3088\u306d\u2026\u2026<\/h2>\n
Iterator \u306f\u5185\u90e8\u306b\u72b6\u614b\u3092\u6301\u3064\u305f\u3081\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5\u3067\u306f\u306a\u3044\u7b48\u3002
\n\u3067\u306f\u306a\u305c Stream \u3067\u4e26\u5217\u5b9f\u884c\u304c\u884c\u3048\u308b\u306e\u3067\u3057\u3087\u3046\u304b\u3002<\/p>\n
\u5148\u307b\u3069\u3001Iterator \u3092 Stream \u306b\u5909\u63db\u3059\u308b\u969b\u306b\u3001\u4e00\u5ea6 Spliterator \u306b\u5909\u63db\u3059\u308b\u65b9\u6cd5\u3092\u7d39\u4ecb\u3057\u307e\u3057\u305f\u3002
\n\u3053\u306e Spliterator \u306e\u4e3b\u306a\u5f79\u5272\u306f\u3001\u5206\u5272\u7d71\u6cbb\u6cd5\u30a2\u30eb\u30b4\u30ea\u30ba\u30e0\u3092\u5229\u7528\u3059\u308b\u305f\u3081\u306bIterator\u3092\u5206\u5272\u3059\u308b\u3053\u3068\u306b\u3042\u308a\u307e\u3059\u3002<\/p>\n
Spliteraotr \u306e\u5206\u5272\u306f Spliterator#trySplit \u3067\u884c\u308f\u308c\u307e\u3059\u304c\u3001Iterator \u3092\u5143\u306b\u3057\u305f Spliterator \u306f trySplit \u30e1\u30bd\u30c3\u30c9\u3067\u306e\u5206\u5272\u6642\u306b\u30d0\u30c3\u30d5\u30a1\u30ea\u30f3\u30b0\u3055\u308c\u3001\u5206\u5272\u5f8c\u306f\u914d\u5217\u3092\u4f7f\u3063\u305f Spliterator \u306b\u5909\u63db\u3055\u308c\u307e\u3059\u3002
\n\u305d\u3057\u3066\u3001Spliterator \u306f\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5\u3067\u306f\u306a\u3044\u305f\u3081 trySplit \u30e1\u30bd\u30c3\u30c9\u304c\u4e26\u5217\u5b9f\u884c\u3055\u308c\u308b\u3053\u3068\u306f\u3042\u308a\u307e\u305b\u3093\u3002<\/p>\n
\n\u4e26\u5217\u30a2\u30eb\u30b4\u30ea\u30ba\u30e0\u3067\u306e\u6709\u7528\u6027\u306f\u660e\u3089\u304b\u3067\u3059\u304c\u3001\u30b9\u30d7\u30ea\u30c3\u30c6\u30ec\u30fc\u30bf\u306f\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5\u3068\u306f\u898b\u306a\u3055\u308c\u307e\u305b\u3093\u3002
\n\u30b9\u30d7\u30ea\u30c3\u30c6\u30ec\u30fc\u30bf\u3092\u4f7f\u7528\u3057\u3066\u4e26\u5217\u30a2\u30eb\u30b4\u30ea\u30ba\u30e0\u3092\u5b9f\u88c5\u3059\u308b\u5834\u5408\u306f\u3001\u4e00\u5ea6\u306b1\u3064\u306e\u30b9\u30ec\u30c3\u30c9\u306e\u307f\u304c\u30b9\u30d7\u30ea\u30c3\u30c6\u30ec\u30fc\u30bf\u3092\u4f7f\u7528\u3059\u308b\u3088\u3046\u306b\u3057\u3066\u304f\u3060\u3055\u3044\u3002
\nhttp:\/\/docs.oracle.com\/javase\/jp\/8\/docs\/api\/java\/util\/Spliterator.html<\/a>\n<\/p><\/blockquote>\n
\u3064\u307e\u308a\u3001Iterator\u304b\u3089\u4f5c\u6210\u3055\u308c\u305fStream\u306e\u5834\u5408\u3001 Stream#parallel() \u3067\u4e26\u5217\u5316\u3055\u308c\u305f\u30b9\u30c8\u30ea\u30fc\u30e0\u3067\u306f\u3001Spliterator#trySplit \u3092\u4f7f\u3063\u3066Iterator\u306b\u30a2\u30af\u30bb\u30b9\u3059\u308b\u969b\u306b\u306f\u4e26\u5217\u51e6\u7406\u306f\u884c\u308f\u308c\u305a\u3001
\n\u4e2d\u9593\u64cd\u4f5c\u3068\u7d42\u7aef\u64cd\u4f5c\u306b\u5bfe\u3057\u3066\u4e26\u5217\u306b\u51e6\u7406\u304c\u884c\u308f\u308c\u308b\u3053\u3068\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n
\u306a\u304a\u3001Iterator \u304b\u3089\u4f5c\u6210\u3057\u305f Spliterator \u3092\u4f7f\u3063\u305f Stream \u306f Collection \u306a\u3069\u304b\u3089\u4f5c\u6210\u3057\u305f Stream \u3068\u6bd4\u3079\u3066\u3001\u4e26\u5217\u51e6\u7406\u306e\u52b9\u7387\u306f\u304b\u306a\u308a\u843d\u3061\u307e\u3059\u3002
\n\u305d\u3082\u305d\u3082\u3001\u3042\u308b\u7a0b\u5ea6\u8981\u7d20\u6570\u304c\u591a\u304f\u306a\u3044\u3068\u4e26\u5217\u51e6\u7406\u3059\u3089\u884c\u3063\u3066\u304f\u308c\u307e\u305b\u3093\u3002<\/p>\n
<\/p>\n
\u4e26\u5217\u51e6\u7406\u3055\u308c\u306a\u3044Stream\u306b\u5909\u63db\u3059\u308b<\/h2>\n
Stream \u306b\u306f\u4e26\u5217\u5b9f\u884c\u3092\u7981\u6b62\u3059\u308b API \u306f\u7528\u610f\u3055\u308c\u3066\u3044\u307e\u305b\u3093\u3002
\n\u305d\u306e\u305f\u3081\u3001\u30b5\u30f3\u30d7\u30eb\u30b3\u30fc\u30c9\u306b\u3042\u3063\u305f digestStream \u30e1\u30bd\u30c3\u30c9\u306e\u3088\u3046\u306b\u3001public \u306b\u516c\u958b\u3059\u308b\u30e1\u30bd\u30c3\u30c9\u304c\u975e\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5\u306a\u4e2d\u9593\u64cd\u4f5c\u3092\u542b\u3093\u3060 Stream \u3092\u8fd4\u3059\u306e\u306f\u5371\u967a\u3067\u3059\u3002<\/p>\n
\u305d\u3093\u306a\u6642\u306f\u3001Stream \u304b\u3089 Spliterator \u3092\u4f5c\u6210\u3057\u3001\u305d\u308c\u3092\u5143\u306b Stream \u3092\u7d44\u307f\u7acb\u3066\u308b\u3053\u3068\u3067\u3001\u4e26\u5217\u51e6\u7406\u53ef\u80fd\u306a<\/strike> \u4e26\u5217\u51e6\u7406\u304c\u884c\u308f\u308c\u306a\u3044 Stream \u306b\u5909\u63db\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002
\n\uff08Iterator\u304b\u3089\u4f5c\u6210\u3057\u305f Spliterator \u3068\u9055\u3063\u3066\u3001\u4e2d\u9593\u64cd\u4f5c\u3092\u542b\u3080 Stream \u306e Stream#spliterator \u3092\u5143\u306b\u3057\u305f Stream \u306f Stream#parallel \u3092\u547c\u3073\u51fa\u3057\u3066\u3082\u4e26\u5217\u306b\u51e6\u7406\u3055\u308c\u308b\u3053\u3068\u306f\u306a\u3044\u3088\u3046\u3067\u3059\uff09<\/p>\n
\r\npublic static void main(String[] a) throws Exception {\r\n    Set set1 = new ConcurrentSkipListSet<>();\r\n    digestStream().parallel().map(String::new).forEach(set1::add);\r\n}\r\n\r\n\/\/ 1\uff5e10000\u307e\u3067\u306e\u6570\u5b57\u6587\u5b57\u5217\u306eSHA-1\u30cf\u30c3\u30b7\u30e5\u5024\u306eStream\u3092\u8fd4\u3059\u3002\r\npublic static Stream digestStream() throws NoSuchAlgorithmException {\r\n    MessageDigest md = MessageDigest.getInstance(\"SHA-1\");\r\n    Stream stream = IntStream.rangeClosed(1, 10000).mapToObj(i -> String.valueOf(i).getBytes()).map(i -> md.digest(i));\r\n    \/\/ map\u4e2d\u9593\u64cd\u4f5c\u307e\u3067\u3092\u542b\u3093\u3060Spliterator\u3092\u4f5c\u6210\u3057\u3001\u305d\u308c\u3092\u30bd\u30fc\u30b9\u3068\u3057\u305fStream\u3092\u8fd4\u3059\u3002\r\n    return StreamSupport.stream(stream.spliterator(), false);\r\n}\r\n<\/pre>\n
<\/p>\n
\u307e\u3068\u3081<\/h2>\n
Stream#parallel() \u3092\u4f7f\u3046\u3068\u3001\u3068\u3066\u3082\u7c21\u5358\u306b\u4e26\u5217\u51e6\u7406\u3092\u884c\u3048\u307e\u3059\u3002
\n\u305f\u3060\u3001\u30de\u30eb\u30c1\u30b9\u30ec\u30c3\u30c9\u3067\u52d5\u4f5c\u3059\u308b\u306e\u3067\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5\u306b\u306a\u308b\u3088\u3046\u5341\u5206\u6c17\u3092\u3064\u3051\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002
\n\u307e\u305f\u3001Stream \u3092\u8fd4\u3059\u30e1\u30bd\u30c3\u30c9\u3092\u4f5c\u308b\u5834\u5408\u3001\u30e1\u30bd\u30c3\u30c9\u5229\u7528\u8005\u5074\u306e\u547c\u3073\u51fa\u3057\u6b21\u7b2c\u3067\u4e26\u5217\u51e6\u7406\u304c\u884c\u308f\u308c\u308b\u53ef\u80fd\u6027\u304c\u3042\u308b\u70b9\u306b\u6ce8\u610f\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
\u3053\u3093\u306b\u3061\u306f\u3001\u5bfa\u5ca1\u3067\u3059\u3002
\n\u4eca\u65e5\u306fJava8\u306eStream\u3092\u4f7f\u3063\u305f\u304a\u624b\u8efd\u306a\u4e26\u5217\u51e6\u7406\u3068\u3001\u3061\u3087\u3063\u3068\u3057\u305f\u6ce8\u610f\u70b9\u3092\u3054\u7d39\u4ecb\u3057\u307e\u3059\u3002<\/p>\n
Stream#parallel() \u3067\u4e26\u5217\u51e6\u7406<\/p>\n
Java8 \u306e Stream#parallel() \u30e1\u30bd\u30c3\u30c9\u3092\u4f7f\u3046\u3068\u3001\u7c21\u5358\u306b\u4e26\u5217\u51e6\u7406\u3092\u884c\u3046\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002
\u7d9a\u304d\u3092\u8aad\u3080...<\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[18],"tags":[57,192],"_links":{"self":[{"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/posts\/9947"}],"collection":[{"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/comments?post=9947"}],"version-history":[{"count":59,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/posts\/9947\/revisions"}],"predecessor-version":[{"id":10023,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/posts\/9947\/revisions\/10023"}],"wp:attachment":[{"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/media?parent=9947"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/categories?post=9947"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.techscore.com\/blog\/wp-json\/wp\/v2\/tags?post=9947"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}