{"id":118678,"date":"2024-03-23T15:20:57","date_gmt":"2024-03-23T06:20:57","guid":{"rendered":"https:\/\/www.silicloud.com\/ja\/blog\/java%e3%81%aereduce%e9%96%a2%e6%95%b0%e3%81%af%e4%bd%95%e3%82%92%e3%81%97%e3%81%be%e3%81%99%e3%81%8b%ef%bc%9f\/"},"modified":"2024-03-28T09:09:43","modified_gmt":"2024-03-28T00:09:43","slug":"java%e3%81%aereduce%e9%96%a2%e6%95%b0%e3%81%af%e4%bd%95%e3%82%92%e3%81%97%e3%81%be%e3%81%99%e3%81%8b%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/ja\/blog\/java%e3%81%aereduce%e9%96%a2%e6%95%b0%e3%81%af%e4%bd%95%e3%82%92%e3%81%97%e3%81%be%e3%81%99%e3%81%8b%ef%bc%9f\/","title":{"rendered":"Java\u306ereduce\u95a2\u6570\u306f\u4f55\u3092\u3057\u307e\u3059\u304b\uff1f"},"content":{"rendered":"

Stream API \u306e\u30e1\u30bd\u30c3\u30c9\u306e 1 \u3064\u3067\u3042\u308b reduce \u95a2\u6570\u306f\u3001\u30b9\u30c8\u30ea\u30fc\u30e0\u5185\u306e\u8981\u7d20\u3092\u6307\u5b9a\u306e\u64cd\u4f5c (\u52a0\u7b97\u3001\u5408\u8a08\u3001\u9023\u7d50\u306a\u3069) \u3067\u7d50\u5408\u3059\u308b\u305f\u3081\u306b\u4f7f\u7528\u3055\u308c\u307e\u3059\u3002reduce \u95a2\u6570\u306f 2 \u9805\u6f14\u7b97\u5b50\u3092\u30d1\u30e9\u30e1\u30fc\u30bf\u30fc\u3068\u3057\u3066\u53d7\u3051\u53d6\u308a\u3001\u521d\u671f\u5024\u3092\u6307\u5b9a\u3067\u304d\u307e\u3059\u3002<\/p>\n

reduce\u95a2\u6570\u306f\u3001\u30b9\u30c8\u30ea\u30fc\u30e0\u5185\u306e\u8981\u7d20\u3092\u9806\u6b21\u53d7\u3051\u53d6\u308a\u3001\u6307\u5b9a\u3055\u308c\u305f2\u9805\u6f14\u7b97\u5b50\u3067\u7d50\u5408\u3057\u3066\u6700\u7d42\u7684\u306a\u7d50\u679c\u3092\u751f\u6210\u3057\u307e\u3059\u3002\u30b9\u30c8\u30ea\u30fc\u30e0\u5185\u306e\u8981\u7d20\u306f\u5de6\u304b\u3089\u53f3\u3078\u9806\u6b21\u7d50\u5408\u3055\u308c\u3001\u6bce\u56de\u524d\u306e\u7d50\u5408\u7d50\u679c\u3068\u73fe\u5728\u306e\u8981\u7d20\u304c2\u9805\u6f14\u7b97\u5b50\u306b\u6e21\u3055\u308c\u307e\u3059\u3002\u3053\u308c\u306b\u3088\u308a\u3001\u3059\u3079\u3066\u306e\u8981\u7d20\u304c\u8a08\u7b97\u306b\u7d44\u307f\u8fbc\u307e\u308c\u3001\u6700\u7d42\u7684\u306b\u306f1\u3064\u306e\u7d50\u679c\u304c\u8fd4\u3055\u308c\u307e\u3059\u3002<\/p>\n

reduce\u95a2\u6570\u3092\u7528\u3044\u3066\u6574\u6570\u306e\u30ea\u30b9\u30c8\u306e\u5408\u8a08\u3092\u6c42\u3081\u308b\u65b9\u6cd5\u306e\u4f8b\u3092\u793a\u3057\u307e\u3059\u3002<\/p>\n

List<Integer>\u00a0numbers\u00a0=\u00a0Arrays.asList(1,\u00a02,\u00a03,\u00a04,\u00a05);<\/pre>\n
int\u00a0sum\u00a0=\u00a0numbers.stream()<\/p>\n
.reduce(0,\u00a0(a,\u00a0b)\u00a0->\u00a0a\u00a0+\u00a0b);<\/p>\n
System.out.println(sum);\u00a0\/\/\u00a0\u8f93\u51fa15<\/p>\n
<\/pre>\n
\u4e0a\u306e\u4f8b\u3067\u306f\u3001\u521d\u671f\u5024\u304c0\u3067\u30012\u9805\u6f14\u7b97\u5b50\u306f\u5358\u7d14\u306a\u52a0\u7b97\u3067\u3059\u3002reduce\u95a2\u6570\u3092\u547c\u3073\u51fa\u3059\u3053\u3068\u3067\u3001\u521d\u671f\u5024\u3068\u30ea\u30b9\u30c8\u306e\u5404\u8981\u7d20\u304c\u9806\u6b21\u52a0\u7b97\u3055\u308c\u3001\u6700\u7d42\u7684\u306b15\u3068\u3044\u3046\u5408\u8a08\u5024\u304c\u5f97\u3089\u308c\u307e\u3059\u3002<\/p>\n
reduce\u95a2\u6570\u306fOptional\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u8fd4\u3059\u306e\u3067\u3001Null\u306e\u53ef\u80fd\u6027\u304c\u3042\u308b\u5834\u5408\u306e\u5bfe\u5fdc\u3092\u9069\u5207\u306a\u65b9\u6cd5\u3067\u884c\u3046\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
Stream API \u306e\u30e1\u30bd\u30c3\u30c9\u306e 1 \u3064\u3067\u3042\u308b reduce \u95a2\u6570\u306f\u3001\u30b9\u30c8\u30ea\u30fc\u30e0\u5185\u306e\u8981\u7d20\u3092\u6307\u5b9a\u306e\u64cd\u4f5c (\u52a0\u7b97\u3001\u5408\u8a08\u3001\u9023\u7d50\u306a\u3069) \u3067\u7d50\u5408\u3059\u308b\u305f\u3081\u306b\u4f7f\u7528\u3055\u308c\u307e\u3059\u3002reduce \u95a2\u6570\u306f 2 \u9805\u6f14\u7b97\u5b50\u3092\u30d1\u30e9\u30e1\u30fc\u30bf\u30fc\u3068\u3057\u3066\u53d7\u3051\u53d6 […]<\/p>\n","protected":false},"author":8,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-118678","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"yoast_head":"\nJava\u306ereduce\u95a2\u6570\u306f\u4f55\u3092\u3057\u307e\u3059\u304b\uff1f - Blog - Silicon Cloud<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.silicloud.com\/ja\/blog\/java\u306ereduce\u95a2\u6570\u306f\u4f55\u3092\u3057\u307e\u3059\u304b\uff1f\/\" \/>\n<meta property=\"og:locale\" content=\"ja_JP\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Java\u306ereduce\u95a2\u6570\u306f\u4f55\u3092\u3057\u307e\u3059\u304b\uff1f\" \/>\n<meta property=\"og:description\" content=\"Stream API \u306e\u30e1\u30bd\u30c3\u30c9\u306e 1 \u3064\u3067\u3042\u308b reduce \u95a2\u6570\u306f\u3001\u30b9\u30c8\u30ea\u30fc\u30e0\u5185\u306e\u8981\u7d20\u3092\u6307\u5b9a\u306e\u64cd\u4f5c (\u52a0\u7b97\u3001\u5408\u8a08\u3001\u9023\u7d50\u306a\u3069) \u3067\u7d50\u5408\u3059\u308b\u305f\u3081\u306b\u4f7f\u7528\u3055\u308c\u307e\u3059\u3002reduce \u95a2\u6570\u306f 2 \u9805\u6f14\u7b97\u5b50\u3092\u30d1\u30e9\u30e1\u30fc\u30bf\u30fc\u3068\u3057\u3066\u53d7\u3051\u53d6 […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.silicloud.com\/ja\/blog\/java\u306ereduce\u95a2\u6570\u306f\u4f55\u3092\u3057\u307e\u3059\u304b\uff1f\/\" \/>\n<meta property=\"og:site_name\" content=\"Blog - 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