{"id":7056,"date":"2026-02-18T10:12:24","date_gmt":"2026-02-18T01:12:24","guid":{"rendered":"https:\/\/dandelions.co.jp\/blog\/?p=7056"},"modified":"2026-02-18T10:12:24","modified_gmt":"2026-02-18T01:12:24","slug":"2026-02-18","status":"publish","type":"post","link":"http:\/\/dandelions.co.jp\/blog\/blog\/2026\/02\/18\/2026-02-18\/","title":{"rendered":"\u6280\u8853\u30d6\u30ed\u30b0 &#8211; \u30e2\u30c0\u30f3Java\u306e\u4fbf\u5229\u306a\u6a5f\u80fd5\u9078"},"content":{"rendered":"\n<p>Java\u306f\u3053\u306e10\u5e74\u3067\u5927\u304d\u304f\u9032\u5316\u3057\u307e\u3057\u305f\u3002\u591a\u304f\u306e\u958b\u767a\u8005\u306f\u3044\u307e\u3060\u306b\u3001\u5197\u9577\u306a\u69cb\u6587\u3084\u5927\u91cf\u306e\u30dc\u30a4\u30e9\u30fc\u30d7\u30ec\u30fc\u30c8\u30b3\u30fc\u30c9\u3092\u9023\u60f3\u3059\u308b\u304b\u3082\u3057\u308c\u307e\u305b\u3093\u304c\u3001\u30e2\u30c0\u30f3Java\uff08Java 8\u4ee5\u964d\uff09\u3067\u306f\u3001\u3088\u308a\u30af\u30ea\u30fc\u30f3\u3067\u5b89\u5168\u3001\u305d\u3057\u3066\u8868\u73fe\u529b\u306e\u9ad8\u3044\u958b\u767a\u3092\u53ef\u80fd\u306b\u3059\u308b\u5f37\u529b\u306a\u6a5f\u80fd\u304c\u5c0e\u5165\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u3053\u306e\u8a18\u4e8b\u3067\u306f\u3001<strong>\u3059\u3079\u3066\u306e\u958b\u767a\u8005\u304c\u77e5\u3063\u3066\u304a\u304f\u3079\u304d5\u3064\u306e\u4fbf\u5229\u306aJava\u6a5f\u80fd<\/strong>\u3092\u7d39\u4ecb\u3057\u307e\u3059\u3002<\/p>\n\n\n<h2>1. \u30e9\u30e0\u30c0\u5f0f\uff08Lambda Expressions\uff09<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>\u30e9\u30e0\u30c0\u5f0f\u3092\u4f7f\u3046\u3053\u3068\u3067\u3001\u7c21\u6f54\u306a\u95a2\u6570\u578b\u30b9\u30bf\u30a4\u30eb\u306e\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u7121\u540d\u30af\u30e9\u30b9\u3092\u4f7f\u3046\u5fc5\u8981\u304c\u306a\u304f\u306a\u308a\u3001\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u304c\u5411\u4e0a\u3057\u307e\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:heading --><\/p>\n<h2>Java 8\u4ee5\u524d:<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:preformatted --><\/p>\n<pre class=\"wp-block-preformatted\">Runnable r = new Runnable() {\n    public void run() {\n        System.out.println(\"Hello World\");\n    }\n};<\/pre>\n<p><!-- \/wp:preformatted --><\/p>\n<p><!-- wp:heading --><\/p>\n<h2>\u30e9\u30e0\u30c0\u5f0f\u3092\u4f7f\u3046\u3068:<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:preformatted --><\/p>\n<pre class=\"wp-block-preformatted\">Runnable r = () -&gt; System.out.println(\"Hello World\");<\/pre>\n<p><!-- \/wp:preformatted --><\/p>\n<p><!-- wp:heading {\"level\":3} --><\/p>\n<h3>\u30e1\u30ea\u30c3\u30c8:<\/h3>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:list --><\/p>\n<ul>\n<li>\u30dc\u30a4\u30e9\u30fc\u30d7\u30ec\u30fc\u30c8\u30b3\u30fc\u30c9\u306e\u524a\u6e1b<\/li>\n<li>\u53ef\u8aad\u6027\u306e\u5411\u4e0a<\/li>\n<li>\u95a2\u6570\u578b\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u306e\u4fc3\u9032<\/li>\n<\/ul>\n<p><!-- \/wp:list --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>\u30e9\u30e0\u30c0\u5f0f\u306f\u3001Stream API\u3084\u30b3\u30ec\u30af\u30b7\u30e7\u30f3\u64cd\u4f5c\u3001\u30a4\u30d9\u30f3\u30c8\u51e6\u7406\u306a\u3069\u3067\u5e83\u304f\u5229\u7528\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:separator --><\/p>\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/><!-- \/wp:separator -->\n<p>\u00a0<\/p>\n<p><!-- wp:heading --><\/p>\n<h2>2. Stream API<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>Stream API\u3092\u4f7f\u7528\u3059\u308b\u3068\u3001\u30b3\u30ec\u30af\u30b7\u30e7\u30f3\u3092\u5ba3\u8a00\u7684\u304b\u3064\u95a2\u6570\u578b\u30b9\u30bf\u30a4\u30eb\u3067\u51e6\u7406\u3067\u304d\u307e\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:heading --><\/p>\n<h2>\u4f8b:<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:preformatted --><\/p>\n<pre class=\"wp-block-preformatted\">List&lt;String&gt; names = List.of(\"Alice\", \"Bob\", \"Andrew\");\n\nnames.stream()\n     .filter(name -&gt; name.startsWith(\"A\"))\n     .map(String::toUpperCase)\n     .forEach(System.out::println);\n<\/pre>\n<p><!-- \/wp:preformatted --><\/p>\n<p><!-- wp:heading {\"level\":3} --><\/p>\n<h3>\u30e1\u30ea\u30c3\u30c8:<\/h3>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:list --><\/p>\n<ul>\n<li>\u660e\u78ba\u3067\u8868\u73fe\u529b\u306e\u9ad8\u3044\u30c7\u30fc\u30bf\u51e6\u7406<\/li>\n<li>\u4e26\u5217\u5b9f\u884c\u306b\u5bfe\u5fdc<\/li>\n<li>\u30a4\u30df\u30e5\u30fc\u30bf\u30d6\u30eb\u306a\u8a2d\u8a08\u3092\u4fc3\u9032<\/li>\n<\/ul>\n<p><!-- \/wp:list --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>Stream\u3092\u4f7f\u3046\u3053\u3068\u3067\u3001\u8907\u96d1\u306a\u30c7\u30fc\u30bf\u5909\u63db\u3082\u8aad\u307f\u3084\u3059\u304f\u4fdd\u5b88\u3057\u3084\u3059\u3044\u30b3\u30fc\u30c9\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:separator --><\/p>\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/><!-- \/wp:separator -->\n<p>\u00a0<\/p>\n<p><!-- wp:heading --><\/p>\n<h2>3. Optional\u30af\u30e9\u30b9<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p><code>Optional<\/code>\u306f\u3001\u5024\u304c\u5b58\u5728\u3059\u308b\u304b\u3069\u3046\u304b\u3092\u660e\u793a\u7684\u306b\u8868\u73fe\u3059\u308b\u3053\u3068\u3067\u3001<code>NullPointerException<\/code>\u3092\u56de\u907f\u3059\u308b\u306e\u306b\u5f79\u7acb\u3061\u307e\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:heading --><\/p>\n<h2>\u4f8b:<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:preformatted --><\/p>\n<pre class=\"wp-block-preformatted\">Optional&lt;String&gt; username = Optional.ofNullable(getUsername());\n\nusername.ifPresent(System.out::println);<\/pre>\n<p><!-- \/wp:preformatted --><\/p>\n<p><!-- wp:heading {\"level\":3} --><\/p>\n<h3>\u91cd\u8981\u306a\u30dd\u30a4\u30f3\u30c8:<\/h3>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:list --><\/p>\n<ul>\n<li>null\u5b89\u5168\u306a\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u3092\u4fc3\u9032<\/li>\n<li>API\u306e\u610f\u56f3\u304c\u660e\u78ba\u306b\u306a\u308b<\/li>\n<li>\u5b9f\u884c\u6642\u30a8\u30e9\u30fc\u306e\u524a\u6e1b<\/li>\n<\/ul>\n<p><!-- \/wp:list --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>\u30e1\u30bd\u30c3\u30c9\u304c<code>null<\/code>\u3092\u8fd4\u3059\u4ee3\u308f\u308a\u306b\u3001<code>Optional&lt;T&gt;<\/code>\u3092\u8fd4\u3059\u3053\u3068\u3067\u3001\u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u53ef\u80fd\u6027\u3092\u660e\u78ba\u306b\u8868\u73fe\u3067\u304d\u307e\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:separator --><\/p>\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/><!-- \/wp:separator -->\n<p>\u00a0<\/p>\n<p><!-- wp:heading --><\/p>\n<h2>4. Records\uff08Java 16\u4ee5\u964d\uff09<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>Record\u306f\u3001\u4e0d\u5909\u306a\u30c7\u30fc\u30bf\u30af\u30e9\u30b9\u3092\u7c21\u6f54\u306b\u4f5c\u6210\u3059\u308b\u305f\u3081\u306e\u6a5f\u80fd\u3067\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:heading --><\/p>\n<h2>\u4f8b:<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:preformatted --><\/p>\n<pre class=\"wp-block-preformatted\">public record User(String name, int age) {}<\/pre>\n<p><!-- \/wp:preformatted --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>\u30b3\u30f3\u30d1\u30a4\u30e9\u304c\u81ea\u52d5\u7684\u306b\u751f\u6210\u3059\u308b\u3082\u306e:<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:list --><\/p>\n<ul>\n<li>\u30b3\u30f3\u30b9\u30c8\u30e9\u30af\u30bf<\/li>\n<li>Getter\u30e1\u30bd\u30c3\u30c9<\/li>\n<li><code>equals()<\/code>\u3068<code>hashCode()<\/code><\/li>\n<li><code>toString()<\/code><\/li>\n<\/ul>\n<p><!-- \/wp:list --><\/p>\n<p><!-- wp:heading {\"level\":3} --><\/p>\n<h3>\u30e1\u30ea\u30c3\u30c8:<\/h3>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:list --><\/p>\n<ul>\n<li>\u30dc\u30a4\u30e9\u30fc\u30d7\u30ec\u30fc\u30c8\u306e\u524a\u6e1b<\/li>\n<li>\u30c7\u30d5\u30a9\u30eb\u30c8\u3067\u30a4\u30df\u30e5\u30fc\u30bf\u30d6\u30eb<\/li>\n<li>DTO\u306b\u6700\u9069<\/li>\n<\/ul>\n<p><!-- \/wp:list --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>Record\u306f\u3001\u30b7\u30f3\u30d7\u30eb\u306a\u30c7\u30fc\u30bf\u4fdd\u6301\u7528\u30af\u30e9\u30b9\u306e\u30e2\u30c7\u30ea\u30f3\u30b0\u306b\u6700\u9069\u3067\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:separator --><\/p>\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/><!-- \/wp:separator -->\n<p>\u00a0<\/p>\n<p><!-- wp:heading --><\/p>\n<h2>5. Switch\u5f0f\uff08Switch Expressions\uff09<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>\u30e2\u30c0\u30f3Java\u3067\u306f\u3001<code>switch<\/code>\u304c\u5024\u3092\u8fd4\u305b\u308b\u3088\u3046\u306b\u306a\u308a\u3001\u30a2\u30ed\u30fc\u69cb\u6587\uff08-&gt;\uff09\u3082\u4f7f\u7528\u3067\u304d\u307e\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:heading --><\/p>\n<h2>\u4f8b:<\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:preformatted --><\/p>\n<pre class=\"wp-block-preformatted\">String dayType = switch (day) {\n    case \"Sat\", \"Sun\" -&gt; \"Weekend\";\n    default -&gt; \"Weekday\";\n};<\/pre>\n<p><!-- \/wp:preformatted --><\/p>\n<p><!-- wp:heading {\"level\":3} --><\/p>\n<h3>\u512a\u308c\u3066\u3044\u308b\u70b9:<\/h3>\n<p><!-- \/wp:heading --><\/p>\n<p><!-- wp:list --><\/p>\n<ul>\n<li>\u3088\u308a\u7c21\u6f54\u306a\u69cb\u6587<\/li>\n<li><code>break<\/code>\u304c\u4e0d\u8981<\/li>\n<li>\u30d0\u30b0\u306e\u6e1b\u5c11<\/li>\n<\/ul>\n<p><!-- \/wp:list --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>Switch\u5f0f\u306f\u53ef\u8aad\u6027\u3092\u5411\u4e0a\u3055\u305b\u3001\u610f\u56f3\u3057\u306a\u3044\u30d5\u30a9\u30fc\u30eb\u30b9\u30eb\u30fc\uff08fall-through\uff09\u306b\u3088\u308b\u30a8\u30e9\u30fc\u3092\u9632\u304e\u307e\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:separator --><\/p>\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/><!-- \/wp:separator -->\n<p>\u00a0<\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>\u30e2\u30c0\u30f3Java\u304c\u76ee\u6307\u3057\u3066\u3044\u308b\u306e\u306f\u3001\u3088\u308a\u30af\u30ea\u30fc\u30f3\u306a\u69cb\u6587\u3001\u3088\u308a\u5b89\u5168\u306a\u30b3\u30fc\u30c9\u3001\u305d\u3057\u3066\u512a\u308c\u305f\u958b\u767a\u8005\u4f53\u9a13\u3067\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>\u3082\u3057\u307e\u3060\u53e4\u3044Java\u306e\u66f8\u304d\u65b9\u3092\u4f7f\u3063\u3066\u3044\u308b\u306a\u3089\u3001\u3053\u308c\u3089\u306e\u6a5f\u80fd\u3092\u53d6\u308a\u5165\u308c\u308b\u3053\u3068\u3067\u3001\u751f\u7523\u6027\u3068\u30b3\u30fc\u30c9\u54c1\u8cea\u3092\u5927\u304d\u304f\u5411\u4e0a\u3055\u305b\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:paragraph --><\/p>\n<p>\u6b21\u56de\u306e\u8a18\u4e8b\u3082\u304a\u697d\u3057\u307f\u306b\uff01<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p><!-- wp:image {\"id\":7067,\"sizeSlug\":\"large\",\"linkDestination\":\"none\"} --><\/p>\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"272\" class=\"wp-image-7067\" src=\"http:\/\/dandelions.co.jp\/blog\/wp\/wp-content\/uploads\/2026\/02\/ChatGPT-Image-2026\u5e742\u670818\u65e5-09_59_38-1024x272.png\" alt=\"\" srcset=\"http:\/\/dandelions.co.jp\/blog\/wp\/wp-content\/uploads\/2026\/02\/ChatGPT-Image-2026\u5e742\u670818\u65e5-09_59_38-1024x272.png 1024w, http:\/\/dandelions.co.jp\/blog\/wp\/wp-content\/uploads\/2026\/02\/ChatGPT-Image-2026\u5e742\u670818\u65e5-09_59_38-300x80.png 300w, http:\/\/dandelions.co.jp\/blog\/wp\/wp-content\/uploads\/2026\/02\/ChatGPT-Image-2026\u5e742\u670818\u65e5-09_59_38-768x204.png 768w, http:\/\/dandelions.co.jp\/blog\/wp\/wp-content\/uploads\/2026\/02\/ChatGPT-Image-2026\u5e742\u670818\u65e5-09_59_38.png 1090w\" sizes=\"(max-width: 767px) 89vw, (max-width: 1000px) 54vw, (max-width: 1071px) 543px, 580px\" \/><\/figure>\n<p><!-- \/wp:image --><\/p>","protected":false},"excerpt":{"rendered":"<p>Java\u306f\u3053\u306e10\u5e74\u3067\u5927\u304d\u304f\u9032\u5316\u3057\u307e\u3057\u305f\u3002\u591a\u304f\u306e\u958b\u767a\u8005\u306f\u3044\u307e\u3060\u306b\u3001\u5197\u9577\u306a\u69cb\u6587\u3084\u5927\u91cf\u306e\u30dc\u30a4\u30e9\u30fc\u30d7\u30ec\u30fc\u30c8\u30b3\u30fc\u30c9\u3092\u9023\u60f3\u3059\u308b\u304b\u3082\u3057\u308c\u307e\u305b\u3093\u304c\u3001\u30e2\u30c0\u30f3Java\uff08Java 8\u4ee5\u964d\uff09\u3067\u306f\u3001\u3088\u308a\u30af\u30ea\u30fc\u30f3\u3067\u5b89\u5168\u3001\u305d\u3057\u3066\u8868\u73fe\u529b\u306e\u9ad8\u3044\u958b\u767a\u3092\u53ef &hellip; <\/p>\n<p class=\"link-more\"><a href=\"http:\/\/dandelions.co.jp\/blog\/blog\/2026\/02\/18\/2026-02-18\/\" class=\"more-link\"><span class=\"screen-reader-text\">&#8220;\u6280\u8853\u30d6\u30ed\u30b0 &#8211; \u30e2\u30c0\u30f3Java\u306e\u4fbf\u5229\u306a\u6a5f\u80fd5\u9078&#8221; \u306e<\/span>\u7d9a\u304d\u3092\u8aad\u3080<\/a><\/p>\n","protected":false},"author":52,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"jetpack_publicize_message":"","jetpack_is_tweetstorm":false,"jetpack_publicize_feature_enabled":true},"categories":[8],"tags":[9],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paR9rw-1PO","_links":{"self":[{"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/posts\/7056"}],"collection":[{"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/users\/52"}],"replies":[{"embeddable":true,"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/comments?post=7056"}],"version-history":[{"count":4,"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/posts\/7056\/revisions"}],"predecessor-version":[{"id":7071,"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/posts\/7056\/revisions\/7071"}],"wp:attachment":[{"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/media?parent=7056"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/categories?post=7056"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/dandelions.co.jp\/blog\/wp-json\/wp\/v2\/tags?post=7056"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}