{"id":341,"date":"2024-10-23T11:44:48","date_gmt":"2024-10-23T02:44:48","guid":{"rendered":"https:\/\/dexall.co.jp\/articles\/?p=341"},"modified":"2025-03-24T08:53:23","modified_gmt":"2025-03-23T23:53:23","slug":"java-optional%e5%ae%8c%e5%85%a8%e3%82%ac%e3%82%a4%e3%83%89%ef%bc%9a5%e3%81%a4%e3%81%ae%e6%b4%bb%e7%94%a8%e6%b3%95%e3%81%a7-null%e3%81%ae%e4%b8%8d%e5%ae%89%e3%81%8b%e3%82%89%e8%a7%a3%e6%94%be%e3%81%95","status":"publish","type":"post","link":"https:\/\/dexall.co.jp\/articles\/?p=341","title":{"rendered":"Java Optional\u5b8c\u5168\u30ac\u30a4\u30c9\uff1a5\u3064\u306e\u6d3b\u7528\u6cd5\u3067 null\u306e\u4e0d\u5b89\u304b\u3089\u89e3\u653e\u3055\u308c\u308b"},"content":{"rendered":"<div id=\"sgb-css-id-1\">\n<div class=\"toc\"><br \/>\n<b>Warning<\/b>:  Undefined array key \"is_admin\" in <b>\/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/sango-theme\/library\/gutenberg\/dist\/classes\/Toc.php<\/b> on line <b>116<\/b><br \/>\n<br \/>\n<b>Warning<\/b>:  Undefined array key \"is_category_top\" in <b>\/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/sango-theme\/library\/gutenberg\/dist\/classes\/Toc.php<\/b> on line <b>121<\/b><br \/>\n<br \/>\n<b>Warning<\/b>:  Undefined array key \"is_top\" in <b>\/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/sango-theme\/library\/gutenberg\/dist\/classes\/Toc.php<\/b> on line <b>128<\/b><br \/>\n    <div id=\"toc_container\" class=\"sgb-toc--bullets js-smooth-scroll\" data-dialog-title=\"\u76ee\u6b21\">\n      <p class=\"toc_title\">\u76ee\u6b21 <\/p>\n      <ul class=\"toc_list\">  <li class=\"first\">    <a href=\"#i-0\">1. Java Optional\u3068\u306f\uff1f\u521d\u5fc3\u8005\u3067\u3082\u308f\u304b\u308b\u57fa\u672c\u6982\u5ff5<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-1\">1.1 Optional\u30af\u30e9\u30b9\u306e\u8a95\u751f\u80cc\u666f\uff1a\u306a\u305cJava 8\u3067\u5c0e\u5165\u3055\u308c\u305f\u306e\u304b<\/a>      <\/li>      <li>        <a href=\"#i-2\">1.2 Optional\u306e\u57fa\u672c\uff1anull\u3092\u5b89\u5168\u306b\u6271\u3046\u305f\u3081\u306e\u65b0\u3057\u3044\u65b9\u6cd5<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-3\">1.3 \u5f93\u6765\u306enull\u30c1\u30a7\u30c3\u30af\u3068Optional\u306e\u6bd4\u8f03\uff1a\u3069\u3053\u304c\u9055\u3046\uff1f<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-4\">2. Java Optional\u306e\u57fa\u672c\u64cd\u4f5c\uff1a5\u3064\u306e\u6d3b\u7528\u6cd5\u3092\u5fb9\u5e95\u89e3\u8aac<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-5\">2.1 \u6d3b\u7528\u6cd51\uff1aof()\u3068ofNullable()\u3067Optional\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4f5c\u6210\u3059\u308b<\/a>      <\/li>      <li>        <a href=\"#i-6\">2.2 \u6d3b\u7528\u6cd52\uff1aisPresent()\u3068ifPresent()\u3067\u5024\u306e\u5b58\u5728\u3092\u78ba\u8a8d\u3057\u51e6\u7406\u3059\u308b<\/a>      <\/li>      <li>        <a href=\"#i-7\">2.3 \u6d3b\u7528\u6cd53\uff1aorElse()\u3068orElseGet()\u3067\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u3092\u63d0\u4f9b\u3059\u308b<\/a>      <\/li>      <li>        <a href=\"#i-8\">2.4 \u6d3b\u7528\u6cd54\uff1amap()\u3068flatMap()\u3067\u5024\u3092\u5909\u63db\u3059\u308b<\/a>      <\/li>      <li>        <a href=\"#i-9\">2.5 \u6d3b\u7528\u6cd55\uff1afilter()\u3067\u6761\u4ef6\u306b\u57fa\u3065\u3044\u3066\u5024\u3092\u30d5\u30a3\u30eb\u30bf\u30ea\u30f3\u30b0\u3059\u308b<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-10\">\u8907\u6570\u306e\u6d3b\u7528\u6cd5\u3092\u7d44\u307f\u5408\u308f\u305b\u305f\u5b9f\u8df5\u4f8b<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-11\">3. Optional\u3092\u4f7f\u3063\u3066\u30b3\u30fc\u30c9\u306e\u54c1\u8cea\u3092\u5411\u4e0a\u3055\u305b\u308b\u5b9f\u8df5\u30c6\u30af\u30cb\u30c3\u30af<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-12\">3.1 \u30e1\u30bd\u30c3\u30c9\u306e\u623b\u308a\u5024\u3068\u3057\u3066Optional\u3092\u4f7f\u7528\u3059\u308b\uff1aAPI\u306e\u8a2d\u8a08\u6539\u5584<\/a>      <\/li>      <li>        <a href=\"#i-13\">3.2 StreamAPI\u3068Optional\u306e\u7d44\u307f\u5408\u308f\u305b\uff1a\u3088\u308a\u8868\u73fe\u529b\u8c4a\u304b\u306a\u30b3\u30fc\u30c9\u306e\u5b9f\u73fe<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-14\">3.3 Optional.stream()\u3092\u6d3b\u7528\u3057\u305f\u30b3\u30ec\u30af\u30b7\u30e7\u30f3\u64cd\u4f5c\u306e\u7c21\u7565\u5316<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-15\">4. Java Optional\u306e\u6ce8\u610f\u70b9\u3068\u843d\u3068\u3057\u7a74\uff1a\u3088\u308a\u5b89\u5168\u306a\u4f7f\u3044\u65b9<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-16\">4.1 Optional\u3092\u30d5\u30a3\u30fc\u30eb\u30c9\u3084\u5f15\u6570\u3068\u3057\u3066\u4f7f\u7528\u3059\u308b\u3053\u3068\u306e\u554f\u984c\u70b9<\/a>      <\/li>      <li>        <a href=\"#i-19\">4.2 get()\u30e1\u30bd\u30c3\u30c9\u306e\u9069\u5207\u306a\u4f7f\u7528\uff1aNoSuchElementException\u3092\u907f\u3051\u308b<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-20\">4.3 Optional\u3068Optional&gt;\uff1a\u30cd\u30b9\u30c8\u3092\u907f\u3051\u308b\u65b9\u6cd5<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-21\">5. Optional\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\uff1anull\u306e\u4e0d\u5b89\u304b\u3089\u5b8c\u5168\u306b\u89e3\u653e\u3055\u308c\u308b\u65b9\u6cd5<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-22\">5.1 Optional.isEmpty()\u306e\u6d3b\u7528\uff1aJava 11\u4ee5\u964d\u3067\u306e\u65b0\u6a5f\u80fd<\/a>      <\/li>      <li>        <a href=\"#i-23\">5.2 orElseThrow()\u3092\u4f7f\u7528\u3057\u305f\u4f8b\u5916\u51e6\u7406\uff1a\u3088\u308a\u660e\u78ba\u306a\u30a8\u30e9\u30fc\u30cf\u30f3\u30c9\u30ea\u30f3\u30b0<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-24\">5.3 \u30c6\u30b9\u30c8\u30b3\u30fc\u30c9\u3067\u306eOptional\u306e\u6271\u3044\uff1a\u3088\u308a\u5805\u7262\u306a\u30e6\u30cb\u30c3\u30c8\u30c6\u30b9\u30c8\u306e\u66f8\u304d\u65b9<\/a>      <\/li>    <\/ul>  <\/li>  <li class=\"last\">    <a href=\"#i-25\">6. \u307e\u3068\u3081\uff1aJava Optional\u3067\u5b9f\u73fe\u3059\u308b\u3001\u3088\u308a\u5b89\u5168\u3067\u7f8e\u3057\u3044\u30b3\u30fc\u30c9\u306e\u4e16\u754c<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-26\">6.1 Optional\u304c\u3082\u305f\u3089\u30595\u3064\u306e\u30e1\u30ea\u30c3\u30c8\uff1a\u518d\u78ba\u8a8d<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-27\">6.2 \u4eca\u5f8c\u306eJava\u958b\u767a\uff1aOptional\u3092\u6d3b\u7528\u3057\u305f\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u6a19\u6e96\u306e\u78ba\u7acb<\/a>      <\/li>    <\/ul>  <\/li><\/ul>\n      <a href=\"#\" class=\"sgb-toc-button js-toc-button\" rel=\"nofollow\" data-open-dialog=\"true\"><i class=\"fa fa-list\"><\/i><span class=\"sgb-toc-button__text\">\u76ee\u6b21\u3078<\/span><\/a>\n    <\/div><\/div><h2 class=\"wp-block-heading\" id=\"i-0\">1. Java Optional\u3068\u306f\uff1f\u521d\u5fc3\u8005\u3067\u3082\u308f\u304b\u308b\u57fa\u672c\u6982\u5ff5<\/h2>\n<\/div>\n\n<div id=\"sgb-css-id-2\">\n<p>Java Optional\u306f\u3001Java 8\u3067\u5c0e\u5165\u3055\u308c\u305f\u9769\u65b0\u7684\u306a\u6a5f\u80fd\u3067\u3001null\u5b89\u5168\u6027\u3092\u9ad8\u3081\u3001\u3088\u308a\u5805\u7262\u306a\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u305f\u3081\u306e\u30c4\u30fc\u30eb\u3067\u3059\u3002\u7c21\u5358\u306b\u8a00\u3048\u3070\u3001Optional\u306f\u300c\u5024\u304c\u3042\u308b\u304b\u3082\u3057\u308c\u306a\u3044\u3057\u3001\u306a\u3044\u304b\u3082\u3057\u308c\u306a\u3044\u300d\u3068\u3044\u3046\u72b6\u6cc1\u3092\u8868\u73fe\u3059\u308b\u30af\u30e9\u30b9\u3067\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-3\">\n<h3 class=\"wp-block-heading\" id=\"i-1\">1.1 Optional\u30af\u30e9\u30b9\u306e\u8a95\u751f\u80cc\u666f\uff1a\u306a\u305cJava 8\u3067\u5c0e\u5165\u3055\u308c\u305f\u306e\u304b<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-4\">\n<p>Java 7\u4ee5\u524d\u3067\u306f\u3001null\u53c2\u7167\u306b\u3088\u308bNullPointerException\u304c\u983b\u767a\u3057\u3001\u958b\u767a\u8005\u3092\u60a9\u307e\u305b\u3066\u3044\u307e\u3057\u305f\u3002\u307e\u305f\u3001null\u30c1\u30a7\u30c3\u30af\u306e\u305f\u3081\u306e\u30b3\u30fc\u30c9\u304c\u5197\u9577\u306b\u306a\u308a\u304c\u3061\u3067\u3001\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u3092\u4e0b\u3052\u308b\u539f\u56e0\u3068\u306a\u3063\u3066\u3044\u307e\u3057\u305f\u3002\u3055\u3089\u306b\u3001null\u304c\u300c\u610f\u56f3\u7684\u306a\u7a7a\u5024\u300d\u306a\u306e\u304b\u300c\u30a8\u30e9\u30fc\u306b\u3088\u308b\u672a\u5b9a\u7fa9\u5024\u300d\u306a\u306e\u304b\u304c\u66d6\u6627\u3067\u3057\u305f\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-5\">\n<p>Java 8\u3067Optional\u304c\u5c0e\u5165\u3055\u308c\u305f\u4e3b\u306a\u7406\u7531\u306f\u4ee5\u4e0b\u306e\u901a\u308a\u3067\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-8\">\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">Java 8\u3067Optional\u304c\u5c0e\u5165\u3055\u308c\u305f\u4e3b\u306a\u7406\u7531<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ol class=\"wp-block-list\"><div id=\"sgb-css-id-6\">\n<li>\u95a2\u6570\u578b\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u306e\u30b5\u30dd\u30fc\u30c8<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-7\">\n<li>Stream API\u3068\u306e\u89aa\u548c\u6027\u306e\u5411\u4e0a<\/li>\n<\/div>\n\n\n<li>\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u3068\u4fdd\u5b88\u6027\u306e\u5411\u4e0a<\/li>\n<\/ol>\n<\/div><\/div>\n<\/div>\n\n<div id=\"sgb-css-id-9\">\n<p>\u3053\u308c\u3089\u306e\u7406\u7531\u306b\u3088\u308a\u3001Optional\u306f\u73fe\u4ee3\u306eJava\u958b\u767a\u306b\u304a\u3044\u3066\u91cd\u8981\u306a\u5f79\u5272\u3092\u679c\u305f\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-10\">\n<h3 class=\"wp-block-heading\" id=\"i-2\">1.2 Optional\u306e\u57fa\u672c\uff1anull\u3092\u5b89\u5168\u306b\u6271\u3046\u305f\u3081\u306e\u65b0\u3057\u3044\u65b9\u6cd5<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-11\">\n<p>Optional\u306f\u3001\u5024\u306e\u5b58\u5728\u3084\u4e0d\u5728\u3092\u660e\u793a\u7684\u306b\u8868\u73fe\u3067\u304d\u308b\u4fbf\u5229\u306a\u30e9\u30c3\u30d1\u30fc\u30af\u30e9\u30b9\u3067\u3059\u3002\u57fa\u672c\u7684\u306a\u4f7f\u3044\u65b9\u306f\u4ee5\u4e0b\u306e\u901a\u308a\u3067\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-12\">\n<p>1.Optional\u306e\u751f\u6210<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ \u975enull\u5024\u3067Optional\u3092\u4f5c\u6210\nOptional&lt;String&gt; optional = Optional.of(\"Hello\");\n\n\/\/ null\u306e\u53ef\u80fd\u6027\u304c\u3042\u308b\u5024\u3067Optional\u3092\u4f5c\u6210\nOptional&lt;String&gt; nullableOptional = Optional.ofNullable(nullableName);\n\n\/\/ \u7a7a\u306eOptional\u3092\u4f5c\u6210\nOptional&lt;String&gt; empty = Optional.empty();<\/pre>\n\n\n<div id=\"sgb-css-id-13\">\n<p>2.\u5024\u306e\u53d6\u5f97\u3068\u51e6\u7406<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ \u5024\u304c\u5b58\u5728\u3059\u308b\u5834\u5408\u306e\u51e6\u7406\noptional.ifPresent(value -&gt; System.out.println(\"Value: \" + value));\n\n\/\/ \u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u3092\u8a2d\u5b9a\nString result = optional.orElse(\"Default\");\n\n\/\/ \u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u5834\u5408\u306b\u4f8b\u5916\u3092\u30b9\u30ed\u30fc\nString value = optional.orElseThrow(() -&gt; new NoSuchElementException());<\/pre>\n\n\n<div id=\"sgb-css-id-14\">\n<h3 class=\"wp-block-heading\" id=\"i-3\">1.3 \u5f93\u6765\u306enull\u30c1\u30a7\u30c3\u30af\u3068Optional\u306e\u6bd4\u8f03\uff1a\u3069\u3053\u304c\u9055\u3046\uff1f<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-15\">\n<p>\u5f93\u6765\u306enull\u30c1\u30a7\u30c3\u30af\u3068Optional\u3092\u4f7f\u7528\u3057\u305f\u65b9\u6cd5\u3092\u6bd4\u8f03\u3057\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ \u5f93\u6765\u306enull\u30c1\u30a7\u30c3\u30af\nif (name != null) {\n    System.out.println(name.toUpperCase());\n} else {\n    System.out.println(\"Name is null\");\n}\n\n\/\/ Optional\u3092\u4f7f\u7528\u3057\u305f\u65b9\u6cd5\nOptional.ofNullable(name)\n    .map(String::toUpperCase)\n    .ifPresentOrElse(\n        System.out::println,\n        () -&gt; System.out.println(\"Name is null\")\n    );<\/pre>\n\n\n<div id=\"sgb-css-id-16\">\n<p>Optional\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u4ee5\u4e0b\u306e\u30e1\u30ea\u30c3\u30c8\u304c\u5f97\u3089\u308c\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-19\">\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">Optional\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u306e\u30e1\u30ea\u30c3\u30c8<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ol class=\"wp-block-list\"><div id=\"sgb-css-id-17\">\n<li>\u30b3\u30fc\u30c9\u306e\u610f\u56f3\u304c\u660e\u78ba\u306b\u306a\u308b\uff1a\u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u53ef\u80fd\u6027\u3092\u578b\u3067\u8868\u73fe<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-18\">\n<li>NullPointerException\u306e\u30ea\u30b9\u30af\u304c\u4f4e\u6e1b\u3059\u308b\uff1a\u5024\u306e\u5b58\u5728\u78ba\u8a8d\u304c\u5f37\u5236\u3055\u308c\u308b<\/li>\n<\/div>\n\n\n<li>\u30e1\u30bd\u30c3\u30c9\u30c1\u30a7\u30fc\u30f3\u306b\u3088\u308b\u7c21\u6f54\u306a\u8a18\u8ff0\u304c\u53ef\u80fd\uff1a\u8907\u96d1\u306a\u6761\u4ef6\u5206\u5c90\u3092\u6e1b\u3089\u305b\u308b<\/li>\n<\/ol>\n<\/div><\/div>\n<\/div>\n\n<div id=\"sgb-css-id-20\">\n<p>Optional\u3092\u9069\u5207\u306b\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u5b89\u5168\u3067\u8aad\u307f\u3084\u3059\u3044\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001Optional\u306e\u5177\u4f53\u7684\u306a\u6d3b\u7528\u6cd5\u306b\u3064\u3044\u3066\u8a73\u3057\u304f\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-21\">\n<h2 class=\"wp-block-heading\" id=\"i-4\">2. Java Optional\u306e\u57fa\u672c\u64cd\u4f5c\uff1a5\u3064\u306e\u6d3b\u7528\u6cd5\u3092\u5fb9\u5e95\u89e3\u8aac<\/h2>\n<\/div>\n\n<div id=\"sgb-css-id-22\">\n<p>Java Optional\u3092\u52b9\u679c\u7684\u306b\u4f7f\u7528\u3059\u308b\u305f\u3081\u306e5\u3064\u306e\u4e3b\u8981\u306a\u6d3b\u7528\u6cd5\u3092\u8a73\u3057\u304f\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002\u3053\u308c\u3089\u306e\u65b9\u6cd5\u3092\u7fd2\u5f97\u3059\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u5b89\u5168\u3067\u8aad\u307f\u3084\u3059\u3044\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-23\">\n<h3 class=\"wp-block-heading\" id=\"i-5\">2.1 \u6d3b\u7528\u6cd51\uff1aof()\u3068ofNullable()\u3067Optional\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4f5c\u6210\u3059\u308b<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-24\">\n<p>Optional\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4f5c\u6210\u3059\u308b\u969b\u3001\u4e3b\u306b2\u3064\u306e\u30e1\u30bd\u30c3\u30c9\u3092\u4f7f\u7528\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<ol class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-25\">\n<li><code>Optional.of(value)<\/code>\uff1a\u975enull\u306e\u5024\u3067Optional\u3092\u4f5c\u6210\u3057\u307e\u3059\u3002<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   Optional&lt;String&gt; opt = Optional.of(\"Hello\");<\/pre>\n\n\n\n<p>\u6ce8\u610f\uff1anull\u3092\u6e21\u3059\u3068NullPointerException\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<ol start=\"2\" class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-26\">\n<li><code>Optional.ofNullable(value)<\/code>\uff1anull\u306e\u53ef\u80fd\u6027\u304c\u3042\u308b\u5024\u3067Optional\u3092\u4f5c\u6210\u3057\u307e\u3059\u3002<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   String nullableValue = getValueFromSomewhere();\n   Optional&lt;String&gt; opt = Optional.ofNullable(nullableValue);<\/pre>\n\n\n<div id=\"sgb-css-id-27\">\n<p>\u7279\u5fb4\uff1anull\u304c\u6e21\u3055\u308c\u305f\u5834\u5408\u3001\u7a7a\u306eOptional\u3092\u8fd4\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-28\">\n<p>\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\uff1a\u5024\u304cnull\u3067\u306a\u3044\u3053\u3068\u304c\u78ba\u5b9f\u306a\u5834\u5408\u306f<code>of()<\/code>\u3092\u3001null\u306e\u53ef\u80fd\u6027\u304c\u3042\u308b\u5834\u5408\u306f<code>ofNullable()<\/code>\u3092\u4f7f\u7528\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-29\">\n<h3 class=\"wp-block-heading\" id=\"i-6\">2.2 \u6d3b\u7528\u6cd52\uff1aisPresent()\u3068ifPresent()\u3067\u5024\u306e\u5b58\u5728\u3092\u78ba\u8a8d\u3057\u51e6\u7406\u3059\u308b<\/h3>\n<\/div>\n\n\n<ol class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-30\">\n<li><code>isPresent()<\/code>\uff1aOptional\u304c\u5024\u3092\u6301\u3063\u3066\u3044\u308b\u304b\u3092boolean\u5024\u3067\u8fd4\u3057\u307e\u3059\u3002<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   if (opt.isPresent()) {\n       System.out.println(\"Value is present: \" + opt.get());\n   }<\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-31\">\n<li><code>ifPresent(Consumer&lt;? super T&gt; consumer)<\/code>\uff1a\u5024\u304c\u5b58\u5728\u3059\u308b\u5834\u5408\u306b\u6307\u5b9a\u3055\u308c\u305f\u51e6\u7406\u3092\u5b9f\u884c\u3057\u307e\u3059\u3002<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   opt.ifPresent(value -&gt; System.out.println(\"Value: \" + value));<\/pre>\n\n\n<div id=\"sgb-css-id-32\">\n<p>\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\uff1a\u53ef\u80fd\u306a\u9650\u308a<code>ifPresent()<\/code>\u3092\u4f7f\u7528\u3057\u3001\u660e\u793a\u7684\u306a<code>isPresent()<\/code>\u30c1\u30a7\u30c3\u30af\u3068<code>get()<\/code>\u306e\u7d44\u307f\u5408\u308f\u305b\u3092\u907f\u3051\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-33\">\n<h3 class=\"wp-block-heading\" id=\"i-7\">2.3 \u6d3b\u7528\u6cd53\uff1aorElse()\u3068orElseGet()\u3067\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u3092\u63d0\u4f9b\u3059\u308b<\/h3>\n<\/div>\n\n\n<ol class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-34\">\n<li><code>orElse(T other)<\/code>\uff1a\u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u5834\u5408\u306b\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u3092\u8fd4\u3057\u307e\u3059\u3002<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   String result = opt.orElse(\"Default\");<\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-35\">\n<li><code>orElseGet(Supplier&lt;? extends T&gt; supplier)<\/code>\uff1a\u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u5834\u5408\u306b\u95a2\u6570\u3092\u5b9f\u884c\u3057\u3066\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u3092\u53d6\u5f97\u3057\u307e\u3059\u3002<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   String result = opt.orElseGet(() -&gt; computeDefaultValue());<\/pre>\n\n\n<div id=\"sgb-css-id-36\">\n<p>\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\uff1a\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u306e\u8a08\u7b97\u306b\u30b3\u30b9\u30c8\u304c\u304b\u304b\u308b\u5834\u5408\u306f<code>orElseGet()<\/code>\u3092\u4f7f\u7528\u3057\u307e\u3057\u3087\u3046\u3002<code>orElse()<\/code>\u306f\u5e38\u306b\u5f15\u6570\u3092\u8a55\u4fa1\u3059\u308b\u305f\u3081\u3001\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306b\u5f71\u97ff\u3092\u4e0e\u3048\u308b\u53ef\u80fd\u6027\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-37\">\n<h3 class=\"wp-block-heading\" id=\"i-8\">2.4 \u6d3b\u7528\u6cd54\uff1amap()\u3068flatMap()\u3067\u5024\u3092\u5909\u63db\u3059\u308b<\/h3>\n<\/div>\n\n\n<ol class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-38\">\n<li><code>map(Function&lt;? super T, ? extends U&gt; mapper)<\/code>\uff1a\u5024\u304c\u5b58\u5728\u3059\u308b\u5834\u5408\u306b\u5909\u63db\u3092\u9069\u7528\u3057\u3001\u65b0\u3057\u3044Optional\u3092\u8fd4\u3057\u307e\u3059\u3002<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   Optional&lt;Integer&gt; length = opt.map(String::length);<\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-39\">\n<li><code>flatMap(Function&lt;? super T, Optional&lt;U&gt;&gt; mapper)<\/code>\uff1a\u5024\u304c\u5b58\u5728\u3059\u308b\u5834\u5408\u306b\u5909\u63db\u3092\u9069\u7528\u3057\u3001\u7d50\u679c\u306eOptional\u3092\u30d5\u30e9\u30c3\u30c8\u5316\u3057\u307e\u3059\u3002<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">   Optional&lt;String&gt; upper = opt.flatMap(this::toUpperCase);\n\n   private Optional&lt;String&gt; toUpperCase(String s) {\n       return Optional.ofNullable(s).map(String::toUpperCase);\n   }<\/pre>\n\n\n<div id=\"sgb-css-id-40\">\n<p>\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\uff1a\u5909\u63db\u7d50\u679c\u304cOptional\u306e\u5834\u5408\u306f<code>flatMap()<\/code>\u3092\u4f7f\u7528\u3057\u3001\u30cd\u30b9\u30c8\u3055\u308c\u305fOptional\u3092\u907f\u3051\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-41\">\n<h3 class=\"wp-block-heading\" id=\"i-9\">2.5 \u6d3b\u7528\u6cd55\uff1afilter()\u3067\u6761\u4ef6\u306b\u57fa\u3065\u3044\u3066\u5024\u3092\u30d5\u30a3\u30eb\u30bf\u30ea\u30f3\u30b0\u3059\u308b<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-42\">\n<p><code>filter(Predicate&lt;? super T&gt; predicate)<\/code>\uff1a\u6761\u4ef6\u306b\u57fa\u3065\u3044\u3066\u5024\u3092\u30d5\u30a3\u30eb\u30bf\u30ea\u30f3\u30b0\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">Optional&lt;String&gt; filtered = opt.filter(s -&gt; s.length() &gt; 5);<\/pre>\n\n\n<div id=\"sgb-css-id-43\">\n<p>\u7279\u5fb4\uff1a\u6761\u4ef6\u3092\u6e80\u305f\u3055\u306a\u3044\u5834\u5408\u306f\u7a7a\u306eOptional\u3092\u8fd4\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-44\">\n<p>\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\uff1a\u8907\u96d1\u306a\u6761\u4ef6\u5206\u5c90\u3092\u7c21\u6f54\u306b\u8868\u73fe\u3059\u308b\u305f\u3081\u306b<code>filter()<\/code>\u3092\u6d3b\u7528\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-45\">\n<h3 class=\"wp-block-heading\" id=\"i-10\">\u8907\u6570\u306e\u6d3b\u7528\u6cd5\u3092\u7d44\u307f\u5408\u308f\u305b\u305f\u5b9f\u8df5\u4f8b<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-46\">\n<p>\u3053\u308c\u3089\u306e\u6d3b\u7528\u6cd5\u3092\u7d44\u307f\u5408\u308f\u305b\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u8868\u73fe\u529b\u8c4a\u304b\u3067\u5b89\u5168\u306a\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">public Optional&lt;String&gt; processName(String input) {\n    return Optional.ofNullable(input)\n        .map(String::trim)\n        .filter(s -&gt; !s.isEmpty())\n        .map(String::toUpperCase)\n        .flatMap(this::addPrefix);\n}\n\nprivate Optional&lt;String&gt; addPrefix(String name) {\n    return Optional.of(\"Mr. \" + name);\n}\n\n\/\/ \u4f7f\u7528\u4f8b\nprocessName(\"  john  \")\n    .ifPresent(System.out::println);  \/\/ \u51fa\u529b: Mr. JOHN\n\nprocessName(\"\")\n    .orElse(\"No name provided\");  \/\/ \u51fa\u529b: No name provided<\/pre>\n\n\n<div id=\"sgb-css-id-47\">\n<p>\u3053\u306e\u4f8b\u3067\u306f\u3001\u5165\u529b\u6587\u5b57\u5217\u3092\u30c8\u30ea\u30e0\u3057\u3001\u7a7a\u3067\u306a\u3044\u5834\u5408\u306b\u5927\u6587\u5b57\u306b\u5909\u63db\u3057\u3001\u63a5\u982d\u8a9e\u3092\u8ffd\u52a0\u3057\u3066\u3044\u307e\u3059\u3002\u5404\u30b9\u30c6\u30c3\u30d7\u3067Optional\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001null\u30c1\u30a7\u30c3\u30af\u3092\u660e\u793a\u7684\u306b\u884c\u3046\u3053\u3068\u306a\u304f\u3001\u5b89\u5168\u306b\u51e6\u7406\u3092\u9032\u3081\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-48\">\n<p>Optional\u306e\u9069\u5207\u306a\u4f7f\u7528\u306f\u3001\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u3092\u5411\u4e0a\u3055\u305b\u3001NullPointerException\u306e\u30ea\u30b9\u30af\u3092\u5927\u5e45\u306b\u6e1b\u5c11\u3055\u305b\u307e\u3059\u3002\u3053\u308c\u3089\u306e\u6d3b\u7528\u6cd5\u3092\u7fd2\u5f97\u3057\u3001\u65e5\u3005\u306e\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u3067\u5b9f\u8df5\u3059\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u5805\u7262\u306aJava\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3092\u958b\u767a\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u3067\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-49\">\n<h2 class=\"wp-block-heading\" id=\"i-11\">3. Optional\u3092\u4f7f\u3063\u3066\u30b3\u30fc\u30c9\u306e\u54c1\u8cea\u3092\u5411\u4e0a\u3055\u305b\u308b\u5b9f\u8df5\u30c6\u30af\u30cb\u30c3\u30af<\/h2>\n<\/div>\n\n<div id=\"sgb-css-id-50\">\n<p>Optional\u3092\u52b9\u679c\u7684\u306b\u6d3b\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u30b3\u30fc\u30c9\u306e\u54c1\u8cea\u3001\u53ef\u8aad\u6027\u3001\u305d\u3057\u3066\u5b89\u5168\u6027\u3092\u5927\u5e45\u306b\u5411\u4e0a\u3055\u305b\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u3053\u3053\u3067\u306f\u3001Optional\u3092\u4f7f\u7528\u3057\u305f3\u3064\u306e\u5b9f\u8df5\u7684\u306a\u30c6\u30af\u30cb\u30c3\u30af\u3092\u7d39\u4ecb\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-51\">\n<h3 class=\"wp-block-heading\" id=\"i-12\">3.1 \u30e1\u30bd\u30c3\u30c9\u306e\u623b\u308a\u5024\u3068\u3057\u3066Optional\u3092\u4f7f\u7528\u3059\u308b\uff1aAPI\u306e\u8a2d\u8a08\u6539\u5584<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-52\">\n<p>\u30e1\u30bd\u30c3\u30c9\u306e\u623b\u308a\u5024\u3068\u3057\u3066Optional\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001API\u306e\u8a2d\u8a08\u3092\u6539\u5584\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">\u5229\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-53\">\n<li>null\u306e\u53ef\u80fd\u6027\u3092\u660e\u793a\u7684\u306b\u8868\u73fe\u3067\u304d\u308b<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-54\">\n<li>API\u306e\u5229\u7528\u8005\u306b\u5024\u306e\u4e0d\u5728\u3092\u8003\u616e\u3059\u308b\u3053\u3068\u3092\u5f37\u5236\u3067\u304d\u308b<\/li>\n<\/div>\n\n\n<li>NullPointerException\u306e\u30ea\u30b9\u30af\u3092\u4f4e\u6e1b\u3067\u304d\u308b<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n<div id=\"sgb-css-id-55\">\n<p>\u4f8b\u3048\u3070\u3001\u30e6\u30fc\u30b6\u30fc\u540d\u3092\u691c\u7d22\u3059\u308b\u30e1\u30bd\u30c3\u30c9\u3092\u8003\u3048\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ \u5f93\u6765\u306e\u65b9\u6cd5\npublic String findUserName(int id) {\n    \/\/ \u30e6\u30fc\u30b6\u30fc\u304c\u898b\u3064\u304b\u3089\u306a\u3044\u5834\u5408\u306fnull\u3092\u8fd4\u3059\n    \/\/ ...\n}\n\n\/\/ Optional\u3092\u4f7f\u7528\u3057\u305f\u65b9\u6cd5\npublic Optional&lt;String&gt; findUserName(int id) {\n    \/\/ \u30e6\u30fc\u30b6\u30fc\u304c\u898b\u3064\u304b\u3089\u306a\u3044\u5834\u5408\u306fOptional.empty()\u3092\u8fd4\u3059\n    \/\/ ...\n}<\/pre>\n\n\n<div id=\"sgb-css-id-56\">\n<p>Optional\u3092\u4f7f\u7528\u3057\u305f\u65b9\u6cd5\u3067\u306f\u3001\u547c\u3073\u51fa\u3057\u5074\u3067\u6b21\u306e\u3088\u3046\u306b\u51e6\u7406\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">findUserName(123).ifPresentOrElse(\n    name -&gt; System.out.println(\"User found: \" + name),\n    () -&gt; System.out.println(\"User not found\")\n);<\/pre>\n\n\n<div id=\"sgb-css-id-58\">\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">\u6ce8\u610f\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-57\">\n<li>\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306b\u82e5\u5e72\u306e\u30aa\u30fc\u30d0\u30fc\u30d8\u30c3\u30c9\u304c\u3042\u308b<\/li>\n<\/div>\n\n\n<li>\u3059\u3079\u3066\u306e\u30e1\u30bd\u30c3\u30c9\u3067Optional\u3092\u4f7f\u7528\u3059\u3079\u304d\u3067\u306f\u306a\u3044\uff08\u4f8b\uff1a\u30b3\u30ec\u30af\u30b7\u30e7\u30f3\u306e\u623b\u308a\u5024\uff09<\/li>\n<\/ul>\n<\/div><\/div>\n<\/div>\n\n<div id=\"sgb-css-id-59\">\n<h3 class=\"wp-block-heading\" id=\"i-13\">3.2 StreamAPI\u3068Optional\u306e\u7d44\u307f\u5408\u308f\u305b\uff1a\u3088\u308a\u8868\u73fe\u529b\u8c4a\u304b\u306a\u30b3\u30fc\u30c9\u306e\u5b9f\u73fe<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-60\">\n<p>StreamAPI\u3068Optional\u3092\u7d44\u307f\u5408\u308f\u305b\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u5ba3\u8a00\u7684\u3067\u8868\u73fe\u529b\u8c4a\u304b\u306a\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:#009EF3;color:#FFF\" class=\"sgb-box-simple__title\">\u4e3b\u306a\u5229\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:#009EF3;background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-61\">\n<li>\u8907\u96d1\u306a\u6761\u4ef6\u5206\u5c90\u3092\u7c21\u6f54\u306b\u8868\u73fe\u3067\u304d\u308b<\/li>\n<\/div>\n\n\n<li>\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u304c\u5411\u4e0a\u3059\u308b<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n<div id=\"sgb-css-id-62\">\n<p>\u4f8b\u3048\u3070\u3001\u30e6\u30fc\u30b6\u30fc\u30ea\u30b9\u30c8\u304b\u3089\u6709\u52b9\u306a\u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u3092\u6301\u3064\u30e6\u30fc\u30b6\u30fc\u306e\u540d\u524d\u3092\u53d6\u5f97\u3059\u308b\u51e6\u7406\u3092\u8003\u3048\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">List&lt;User&gt; users = getUserList();\nList&lt;String&gt; validUserNames = users.stream()\n    .map(User::getEmail)\n    .filter(Optional::isPresent)\n    .map(Optional::get)\n    .filter(email -&gt; email.contains(\"@\"))\n    .map(email -&gt; email.split(\"@\")[0])\n    .collect(Collectors.toList());<\/pre>\n\n\n<div id=\"sgb-css-id-63\">\n<p>\u3053\u306e\u30b3\u30fc\u30c9\u3067\u306f\u3001<code>Optional::isPresent<\/code>\u3068<code>Optional::get<\/code>\u3092\u4f7f\u7528\u3057\u3066\u3001\u5b58\u5728\u3059\u308b\u5024\u306e\u307f\u3092\u51e6\u7406\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-64\">\n<h3 class=\"wp-block-heading\" id=\"i-14\">3.3 Optional.stream()\u3092\u6d3b\u7528\u3057\u305f\u30b3\u30ec\u30af\u30b7\u30e7\u30f3\u64cd\u4f5c\u306e\u7c21\u7565\u5316<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-65\">\n<p>Java 9\u3067\u5c0e\u5165\u3055\u308c\u305f<code>Optional.stream()<\/code>\u30e1\u30bd\u30c3\u30c9\u3092\u4f7f\u7528\u3059\u308b\u3068\u3001Optional\u3092\u542b\u3080\u30b3\u30ec\u30af\u30b7\u30e7\u30f3\u306e\u64cd\u4f5c\u3092\u3055\u3089\u306b\u7c21\u7565\u5316\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:#009EF3;color:#FFF\" class=\"sgb-box-simple__title\">\u4e3b\u306a\u5229\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:#009EF3;background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-66\">\n<li>\u30b3\u30ec\u30af\u30b7\u30e7\u30f3\u64cd\u4f5c\u3092\u7c21\u7565\u5316\u3067\u304d\u308b<\/li>\n<\/div>\n\n\n<li>null\u30c1\u30a7\u30c3\u30af\u3068\u30d5\u30a3\u30eb\u30bf\u30ea\u30f3\u30b0\u3092\u4e00\u5ea6\u306b\u884c\u3048\u308b<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n<div id=\"sgb-css-id-67\">\n<p>\u4f8b\u3048\u3070\u3001Optional\u306e\u8981\u7d20\u3092\u542b\u3080\u30ea\u30b9\u30c8\u304b\u3089\u3001\u5b58\u5728\u3059\u308b\u5024\u306e\u307f\u3092\u53d6\u308a\u51fa\u3059\u51e6\u7406\u3092\u8003\u3048\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">List&lt;Optional&lt;String&gt;&gt; optionalList = Arrays.asList(\n    Optional.of(\"apple\"),\n    Optional.empty(),\n    Optional.of(\"banana\")\n);\n\nList&lt;String&gt; result = optionalList.stream()\n    .flatMap(Optional::stream)\n    .collect(Collectors.toList());\n\nSystem.out.println(result);  \/\/ \u51fa\u529b: [apple, banana]<\/pre>\n\n\n\n<p>\u3053\u306e\u4f8b\u3067\u306f\u3001<code>Optional::stream<\/code>\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u5b58\u5728\u3059\u308b\u5024\u306e\u307f\u3092\u7c21\u5358\u306b\u53d6\u308a\u51fa\u3059\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:#ffb36b;color:#FFF\" class=\"sgb-box-simple__title\">\u6ce8\u610f\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:#ffb36b;background-color:#FFF\"><div id=\"sgb-css-id-68\">\n<p>Java 8\u4ee5\u524d\u3067\u306f\u4f7f\u7528\u3067\u304d\u306a\u3044\u305f\u3081\u3001\u4e92\u63db\u6027\u306b\u6ce8\u610f\u304c\u5fc5\u8981\u3067\u3059<\/p>\n<\/div><\/div><\/div>\n\n\n<div id=\"sgb-css-id-69\">\n<p>\u3053\u308c\u3089\u306e\u30c6\u30af\u30cb\u30c3\u30af\u3092\u9069\u5207\u306b\u6d3b\u7528\u3059\u308b\u3053\u3068\u3067\u3001Optional\u306e\u771f\u306e\u529b\u3092\u5f15\u304d\u51fa\u3057\u3001\u3088\u308a\u5b89\u5168\u3067\u8868\u73fe\u529b\u8c4a\u304b\u306a\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u305f\u3060\u3057\u3001Optional\u306e\u904e\u5270\u4f7f\u7528\u306f\u907f\u3051\u3001\u9069\u5207\u306a\u5834\u9762\u3067\u9069\u5207\u306b\u4f7f\u7528\u3059\u308b\u3053\u3068\u304c\u91cd\u8981\u3067\u3059\u3002\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001Optional\u3092\u4f7f\u7528\u3059\u308b\u969b\u306e\u6ce8\u610f\u70b9\u3068\u843d\u3068\u3057\u7a74\u306b\u3064\u3044\u3066\u8a73\u3057\u304f\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-70\">\n<h2 class=\"wp-block-heading\" id=\"i-15\">4. Java Optional\u306e\u6ce8\u610f\u70b9\u3068\u843d\u3068\u3057\u7a74\uff1a\u3088\u308a\u5b89\u5168\u306a\u4f7f\u3044\u65b9<\/h2>\n<\/div>\n\n<div id=\"sgb-css-id-71\">\n<p>Optional\u306f\u5f37\u529b\u306a\u30c4\u30fc\u30eb\u3067\u3059\u304c\u3001\u9069\u5207\u306b\u4f7f\u7528\u3057\u306a\u3044\u3068\u65b0\u305f\u306a\u554f\u984c\u3092\u5f15\u304d\u8d77\u3053\u3059\u53ef\u80fd\u6027\u304c\u3042\u308a\u307e\u3059\u3002\u3053\u3053\u3067\u306f\u3001Optional\u3092\u4f7f\u7528\u3059\u308b\u969b\u306e\u4e3b\u306a\u6ce8\u610f\u70b9\u3068\u3001\u305d\u308c\u3089\u3092\u56de\u907f\u3059\u308b\u305f\u3081\u306e\u65b9\u6cd5\u3092\u89e3\u8aac\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-72\">\n<h3 class=\"wp-block-heading\" id=\"i-16\">4.1 Optional\u3092\u30d5\u30a3\u30fc\u30eb\u30c9\u3084\u5f15\u6570\u3068\u3057\u3066\u4f7f\u7528\u3059\u308b\u3053\u3068\u306e\u554f\u984c\u70b9<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-73\">\n<h4 class=\"wp-block-heading\" id=\"i-17\">\u30d5\u30a3\u30fc\u30eb\u30c9\u3068\u3057\u3066\u306eOptional<\/h4>\n<\/div>\n\n<div id=\"sgb-css-id-74\">\n<p>Optional\u3092\u30af\u30e9\u30b9\u306e\u30d5\u30a3\u30fc\u30eb\u30c9\u3068\u3057\u3066\u4f7f\u7528\u3059\u308b\u3053\u3068\u306f\u63a8\u5968\u3055\u308c\u307e\u305b\u3093\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-77\">\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">\u554f\u984c\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-75\">\n<li>\u30b7\u30ea\u30a2\u30e9\u30a4\u30ba\u4e0d\u53ef\u80fd<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-76\">\n<li>\u4e0d\u5fc5\u8981\u306a\u30dc\u30af\u30b7\u30f3\u30b0\/\u30a2\u30f3\u30dc\u30af\u30b7\u30f3\u30b0\u306b\u3088\u308b\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u4f4e\u4e0b<\/li>\n<\/div>\n\n\n<li>\u30b3\u30fc\u30c9\u306e\u8907\u96d1\u6027\u304c\u5897\u3059<\/li>\n<\/ul>\n<\/div><\/div>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ \u60aa\u3044\u4f8b\npublic class User {\n    private Optional&lt;String&gt; middleName; \/\/ \u63a8\u5968\u3055\u308c\u306a\u3044\n}\n\n\/\/ \u826f\u3044\u4f8b\npublic class User {\n    private String middleName; \/\/ null\u3092\u8a31\u5bb9\n\n    public Optional&lt;String&gt; getMiddleName() {\n        return Optional.ofNullable(middleName);\n    }\n}<\/pre>\n\n\n<div id=\"sgb-css-id-78\">\n<h4 class=\"wp-block-heading\" id=\"i-18\">\u5f15\u6570\u3068\u3057\u3066\u306eOptional<\/h4>\n<\/div>\n\n<div id=\"sgb-css-id-79\">\n<p>\u30e1\u30bd\u30c3\u30c9\u306e\u5f15\u6570\u3068\u3057\u3066Optional\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3082\u907f\u3051\u308b\u3079\u304d\u3067\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-82\">\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">\u554f\u984c\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-80\">\n<li>API\u306e\u8907\u96d1\u6027\u304c\u5897\u3059<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-81\">\n<li>\u547c\u3073\u51fa\u3057\u5074\u3067\u306eOptional\u4f5c\u6210\u304c\u5fc5\u8981\u306b\u306a\u308b<\/li>\n<\/div>\n\n\n<li>null\u304c\u8a31\u5bb9\u3055\u308c\u308b\u306e\u304bOptional.empty()\u304c\u8a31\u5bb9\u3055\u308c\u308b\u306e\u304b\u4e0d\u660e\u78ba\u306b\u306a\u308b<\/li>\n<\/ul>\n<\/div><\/div>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ \u60aa\u3044\u4f8b\npublic void processUser(Optional&lt;User&gt; user) { ... }\n\n\/\/ \u826f\u3044\u4f8b\npublic void processUser(User user) { ... }\npublic void processUserIfPresent(User user) { ... } \/\/ user\u304cnull\u306e\u5834\u5408\u306f\u4f55\u3082\u3057\u306a\u3044<\/pre>\n\n\n<div id=\"sgb-css-id-83\">\n<h3 class=\"wp-block-heading\" id=\"i-19\">4.2 get()\u30e1\u30bd\u30c3\u30c9\u306e\u9069\u5207\u306a\u4f7f\u7528\uff1aNoSuchElementException\u3092\u907f\u3051\u308b<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-84\">\n<p><code>Optional.get()<\/code>\u30e1\u30bd\u30c3\u30c9\u306f\u3001\u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u5834\u5408\u306b<code>NoSuchElementException<\/code>\u3092\u30b9\u30ed\u30fc\u3057\u307e\u3059\u3002\u3053\u306e\u30e1\u30bd\u30c3\u30c9\u306e\u4f7f\u7528\u306f\u907f\u3051\u3001\u3088\u308a\u5b89\u5168\u306a\u4ee3\u66ff\u624b\u6bb5\u3092\u4f7f\u7528\u3059\u3079\u304d\u3067\u3059\u3002<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ \u60aa\u3044\u4f8b\nOptional&lt;String&gt; name = getNameOptional();\nString result = name.get(); \/\/ \u5371\u967a\uff1aNoSuchElementException\u306e\u53ef\u80fd\u6027\u3042\u308a\n\n\/\/ \u826f\u3044\u4f8b\nString result = name.orElse(\"Default Name\");\n\/\/ \u307e\u305f\u306f\nString result = name.orElseThrow(() -&gt; new CustomException(\"Name not found\"));<\/pre>\n\n\n<div id=\"sgb-css-id-86\">\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-85\">\n<li><code>isPresent()<\/code>\u3068<code>get()<\/code>\u306e\u7d44\u307f\u5408\u308f\u305b\u3092\u907f\u3051\u308b<\/li>\n<\/div>\n\n\n<li><code>orElse()<\/code>, <code>orElseGet()<\/code>, <code>orElseThrow()<\/code>\u306a\u3069\u306e\u5b89\u5168\u306a\u30e1\u30bd\u30c3\u30c9\u3092\u4f7f\u7528\u3059\u308b<\/li>\n<\/ul>\n<\/div><\/div>\n<\/div>\n\n<div id=\"sgb-css-id-87\">\n<h3 class=\"wp-block-heading\" id=\"i-20\">4.3 Optional\u3068Optional&gt;\uff1a\u30cd\u30b9\u30c8\u3092\u907f\u3051\u308b\u65b9\u6cd5<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-88\">\n<p>Optional\u306e\u30cd\u30b9\u30c8\u306f\u907f\u3051\u308b\u3079\u304d\u3067\u3059\u3002\u30cd\u30b9\u30c8\u3055\u308c\u305fOptional\u306f\u3001\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u3092\u4f4e\u4e0b\u3055\u305b\u3001\u4e0d\u5fc5\u8981\u306a\u8907\u96d1\u6027\u3092\u5897\u52a0\u3055\u305b\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-89\">\n<p><strong>\u554f\u984c\u306e\u3042\u308b\u4f8b\uff1a<\/strong><\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">Optional&lt;Optional&lt;String&gt;&gt; nested = Optional.of(Optional.of(\"value\"));<\/pre>\n\n\n<div id=\"sgb-css-id-90\">\n<p><strong>\u30cd\u30b9\u30c8\u3092\u907f\u3051\u308b\u65b9\u6cd5\uff1a<\/strong><\/p>\n<\/div>\n\n\n<ol class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-91\">\n<li><code>flatMap()<\/code>\u3092\u4f7f\u7528\u3057\u3066\u5e73\u5766\u5316\u3059\u308b<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">Optional&lt;String&gt; result = nested.flatMap(opt -&gt; opt);<\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-92\">\n<li><code>map()<\/code>\u3092\u4f7f\u7528\u3057\u3066\u5185\u90e8\u306eOptional\u3092\u51e6\u7406\u3059\u308b<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">Optional&lt;String&gt; result = nested.map(opt -&gt; opt.orElse(\"default\"));<\/pre>\n\n\n\n<ol start=\"3\" class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-93\">\n<li>\u8a2d\u8a08\u3092\u898b\u76f4\u3057\u3001\u30cd\u30b9\u30c8\u304c\u5fc5\u8981\u306a\u3044\u65b9\u6cd5\u3092\u691c\u8a0e\u3059\u308b<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ \u30cd\u30b9\u30c8\u306e\u4ee3\u308f\u308a\u306b\npublic Optional&lt;String&gt; findValue() {\n    String value = \/\/ \u5024\u3092\u53d6\u5f97\u3059\u308b\u51e6\u7406\n    return Optional.ofNullable(value);\n}<\/pre>\n\n\n<div id=\"sgb-css-id-94\">\n<p>Optional\u3092\u9069\u5207\u306b\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u30b3\u30fc\u30c9\u306e\u5b89\u5168\u6027\u3068\u53ef\u8aad\u6027\u3092\u5411\u4e0a\u3055\u305b\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u305f\u3060\u3057\u3001Optional\u306e\u904e\u5270\u4f7f\u7528\u3084\u4e0d\u9069\u5207\u306a\u4f7f\u7528\u306f\u3001\u304b\u3048\u3063\u3066\u30b3\u30fc\u30c9\u3092\u8907\u96d1\u306b\u3059\u308b\u53ef\u80fd\u6027\u304c\u3042\u308a\u307e\u3059\u3002\u3053\u308c\u3089\u306e\u6ce8\u610f\u70b9\u3092\u5ff5\u982d\u306b\u7f6e\u304d\u3001\u9069\u5207\u306a\u5834\u9762\u3067\u9069\u5207\u306b\u4f7f\u7528\u3059\u308b\u3053\u3068\u304c\u91cd\u8981\u3067\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-95\">\n<p>\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001Optional\u3092\u4f7f\u7528\u3059\u308b\u969b\u306e\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\u306b\u3064\u3044\u3066\u8a73\u3057\u304f\u898b\u3066\u3044\u304d\u307e\u3059\u3002\u3053\u308c\u3089\u306e\u5b9f\u8df5\u7684\u306a\u30c6\u30af\u30cb\u30c3\u30af\u3092\u7fd2\u5f97\u3059\u308b\u3053\u3068\u3067\u3001Optional\u306e\u5229\u70b9\u3092\u6700\u5927\u9650\u306b\u6d3b\u7528\u3057\u3001\u3088\u308a\u5805\u7262\u306aJava\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3092\u958b\u767a\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u3067\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-96\">\n<h2 class=\"wp-block-heading\" id=\"i-21\">5. Optional\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\uff1anull\u306e\u4e0d\u5b89\u304b\u3089\u5b8c\u5168\u306b\u89e3\u653e\u3055\u308c\u308b\u65b9\u6cd5<\/h2>\n<\/div>\n\n<div id=\"sgb-css-id-97\">\n<p>Optional\u3092\u9069\u5207\u306b\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001null\u306e\u4e0d\u5b89\u304b\u3089\u89e3\u653e\u3055\u308c\u3001\u3088\u308a\u5b89\u5168\u3067\u8aad\u307f\u3084\u3059\u3044\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u3053\u3053\u3067\u306f\u3001Optional\u3092\u6700\u5927\u9650\u306b\u6d3b\u7528\u3059\u308b\u305f\u3081\u306e\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\u3092\u7d39\u4ecb\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-98\">\n<h3 class=\"wp-block-heading\" id=\"i-22\">5.1 Optional.isEmpty()\u306e\u6d3b\u7528\uff1aJava 11\u4ee5\u964d\u3067\u306e\u65b0\u6a5f\u80fd<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-99\">\n<p>Java 11\u3067\u5c0e\u5165\u3055\u308c\u305f<code>isEmpty()<\/code>\u30e1\u30bd\u30c3\u30c9\u306f\u3001Optional\u304c\u7a7a\u304b\u3069\u3046\u304b\u3092\u5224\u5b9a\u3059\u308b\u305f\u3081\u306e\u7c21\u6f54\u306a\u65b9\u6cd5\u3092\u63d0\u4f9b\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:#009EF3;color:#FFF\" class=\"sgb-box-simple__title\">\u5229\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:#009EF3;background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-100\">\n<li><code>isPresent()<\/code>\u306e\u5426\u5b9a\u3088\u308a\u3082\u53ef\u8aad\u6027\u304c\u5411\u4e0a\u3059\u308b<\/li>\n<\/div>\n\n\n<li>\u30b3\u30fc\u30c9\u306e\u610f\u56f3\u304c\u3088\u308a\u660e\u78ba\u306b\u306a\u308b<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ Java 11\u4ee5\u964d\nif (optional.isEmpty()) {\n    \/\/ Optional\u304c\u7a7a\u306e\u5834\u5408\u306e\u51e6\u7406\n}\n\n\/\/ Java 8-10 (\u307e\u305f\u306f11\u4ee5\u964d\u3067\u3082\u4f7f\u7528\u53ef\u80fd)\nif (!optional.isPresent()) {\n    \/\/ Optional\u304c\u7a7a\u306e\u5834\u5408\u306e\u51e6\u7406\n}<\/pre>\n\n\n<div id=\"sgb-css-id-101\">\n<p>\u6ce8\u610f\u70b9\uff1aJava 8-10\u3067\u306f\u4f7f\u7528\u3067\u304d\u306a\u3044\u305f\u3081\u3001\u30d0\u30fc\u30b8\u30e7\u30f3\u4e92\u63db\u6027\u306b\u6ce8\u610f\u304c\u5fc5\u8981\u3067\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-102\">\n<h3 class=\"wp-block-heading\" id=\"i-23\">5.2 orElseThrow()\u3092\u4f7f\u7528\u3057\u305f\u4f8b\u5916\u51e6\u7406\uff1a\u3088\u308a\u660e\u78ba\u306a\u30a8\u30e9\u30fc\u30cf\u30f3\u30c9\u30ea\u30f3\u30b0<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-103\">\n<p><code>orElseThrow()<\/code>\u30e1\u30bd\u30c3\u30c9\u3092\u4f7f\u7528\u3059\u308b\u3068\u3001\u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u5834\u5408\u306b\u6307\u5b9a\u3057\u305f\u4f8b\u5916\u3092\u30b9\u30ed\u30fc\u3067\u304d\u307e\u3059\u3002\u3053\u308c\u306b\u3088\u308a\u3001\u3088\u308a\u660e\u78ba\u306a\u30a8\u30e9\u30fc\u30cf\u30f3\u30c9\u30ea\u30f3\u30b0\u304c\u53ef\u80fd\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:#009EF3;color:#FFF\" class=\"sgb-box-simple__title\">\u5229\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:#009EF3;background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-104\">\n<li>\u30ab\u30b9\u30bf\u30e0\u4f8b\u5916\u3092\u4f7f\u7528\u3057\u3066\u3088\u308a\u5177\u4f53\u7684\u306a\u30a8\u30e9\u30fc\u60c5\u5831\u3092\u63d0\u4f9b\u3067\u304d\u308b<\/li>\n<\/div>\n\n\n<li>\u30b3\u30fc\u30c9\u306e\u610f\u56f3\u304c\u660e\u78ba\u306b\u306a\u308a\u3001\u30c7\u30d0\u30c3\u30b0\u304c\u5bb9\u6613\u306b\u306a\u308b<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">public String getUserName(int id) throws UserNotFoundException {\n    return userRepository.findById(id)\n        .map(User::getName)\n        .orElseThrow(() -&gt; new UserNotFoundException(\"User not found with id: \" + id));\n}<\/pre>\n\n\n<div id=\"sgb-css-id-105\">\n<p>\u3053\u306e\u30a2\u30d7\u30ed\u30fc\u30c1\u306f\u3001\u5358\u306b<code>null<\/code>\u3092\u8fd4\u3059\u3088\u308a\u3082\u3001\u547c\u3073\u51fa\u3057\u5143\u306b\u660e\u78ba\u306a\u60c5\u5831\u3092\u63d0\u4f9b\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-106\">\n<h3 class=\"wp-block-heading\" id=\"i-24\">5.3 \u30c6\u30b9\u30c8\u30b3\u30fc\u30c9\u3067\u306eOptional\u306e\u6271\u3044\uff1a\u3088\u308a\u5805\u7262\u306a\u30e6\u30cb\u30c3\u30c8\u30c6\u30b9\u30c8\u306e\u66f8\u304d\u65b9<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-107\">\n<p>Optional\u3092\u4f7f\u7528\u3057\u305f\u30b3\u30fc\u30c9\u306e\u30c6\u30b9\u30c8\u306f\u3001\u901a\u5e38\u306e<code>null<\/code>\u30c1\u30a7\u30c3\u30af\u3068\u306f\u7570\u306a\u308b\u30a2\u30d7\u30ed\u30fc\u30c1\u304c\u5fc5\u8981\u3067\u3059\u3002\u9069\u5207\u306a\u30c6\u30b9\u30c8\u65b9\u6cd5\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u30b3\u30fc\u30c9\u306e\u4fe1\u983c\u6027\u3092\u9ad8\u3081\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<ol class=\"wp-block-list is-style-sango-list-simple\"><div id=\"sgb-css-id-108\">\n<li>\u5024\u304c\u5b58\u5728\u3059\u308b\u5834\u5408\u306e\u30c6\u30b9\u30c8<\/li>\n<\/div><\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">@Test\nvoid testPresentValue() {\n    Optional&lt;String&gt; optional = Optional.of(\"test\");\n    assertTrue(optional.isPresent());\n    assertEquals(\"test\", optional.get());\n}<\/pre>\n\n\n<div id=\"sgb-css-id-109\">\n<ol start=\"2\" class=\"wp-block-list is-style-sango-list-simple\">\n<li>\u7a7a\u306eOptional\u306e\u30c6\u30b9\u30c8<\/li>\n<\/ol>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">@Test\nvoid testEmptyOptional() {\n    Optional&lt;String&gt; optional = Optional.empty();\n    assertTrue(optional.isEmpty()); \/\/ Java 11\u4ee5\u964d\n    assertFalse(optional.isPresent()); \/\/ \u3059\u3079\u3066\u306e\u30d0\u30fc\u30b8\u30e7\u30f3\n}<\/pre>\n\n\n<div id=\"sgb-css-id-110\">\n<ol start=\"3\" class=\"wp-block-list is-style-sango-list-simple\">\n<li><code>orElseThrow()<\/code>\u3092\u4f7f\u7528\u3057\u305f\u4f8b\u5916\u306e\u30c6\u30b9\u30c8<\/li>\n<\/ol>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">@Test\nvoid testOrElseThrow() {\n    Optional&lt;String&gt; optional = Optional.empty();\n    assertThrows(NoSuchElementException.class, () -&gt; optional.orElseThrow());\n}<\/pre>\n\n\n\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">\u30c6\u30b9\u30c8\u306e\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-111\">\n<li>\u5883\u754c\u5024\u306e\u30c6\u30b9\u30c8\u3092\u5fd8\u308c\u305a\u306b\u884c\u3046\uff08\u7a7a\u306e\u5834\u5408\u3001\u5024\u304c\u5b58\u5728\u3059\u308b\u5834\u5408\uff09<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-112\">\n<li>\u30e2\u30c3\u30af\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4f7f\u7528\u3057\u3066Optional\u3092\u8fd4\u3059\u30e1\u30bd\u30c3\u30c9\u3092\u30c6\u30b9\u30c8\u3059\u308b<\/li>\n<\/div>\n\n\n<li>\u30c6\u30b9\u30c8\u306e\u53ef\u8aad\u6027\u3092\u9ad8\u3081\u308b\u305f\u3081\u306e\u30ab\u30b9\u30bf\u30e0\u30a2\u30b5\u30fc\u30b7\u30e7\u30f3\u3092\u4f5c\u6210\u3059\u308b<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">public static void assertOptionalContains(Optional&lt;?&gt; optional, Object expected) {\n    assertTrue(optional.isPresent(), \"Optional should be present\");\n    assertEquals(expected, optional.get(), \"Optional value should match expected\");\n}<\/pre>\n\n\n<div id=\"sgb-css-id-113\">\n<p>JUnit 5\u3068AssertJ\u3092\u7d44\u307f\u5408\u308f\u305b\u3066\u4f7f\u7528\u3059\u308b\u3068\u3001\u3088\u308a\u8868\u73fe\u529b\u8c4a\u304b\u3067\u8aad\u307f\u3084\u3059\u3044\u30c6\u30b9\u30c8\u3092\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">import static org.assertj.core.api.Assertions.*;\n\n@Test\nvoid testOptionalWithAssertJ() {\n    Optional&lt;String&gt; optional = Optional.of(\"test\");\n    assertThat(optional)\n        .isPresent()\n        .hasValue(\"test\");\n}<\/pre>\n\n\n<div id=\"sgb-css-id-114\">\n<p>\u3053\u308c\u3089\u306e\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\u3092\u9069\u7528\u3059\u308b\u3053\u3068\u3067\u3001Optional\u3092\u4f7f\u7528\u3057\u305f\u30b3\u30fc\u30c9\u306e\u54c1\u8cea\u3068\u4fe1\u983c\u6027\u3092\u5927\u5e45\u306b\u5411\u4e0a\u3055\u305b\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<code>null<\/code>\u306e\u4e0d\u5b89\u304b\u3089\u89e3\u653e\u3055\u308c\u308b\u3060\u3051\u3067\u306a\u304f\u3001\u30b3\u30fc\u30c9\u306e\u610f\u56f3\u304c\u3088\u308a\u660e\u78ba\u306b\u306a\u308a\u3001\u30d0\u30b0\u306e\u767a\u898b\u3082\u5bb9\u6613\u306b\u306a\u308a\u307e\u3059\u3002\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001\u3053\u308c\u3089\u306e\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\u3092\u5b9f\u969b\u306e\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u306b\u9069\u7528\u3059\u308b\u65b9\u6cd5\u3068\u3001\u305d\u306e\u52b9\u679c\u306b\u3064\u3044\u3066\u8a73\u3057\u304f\u898b\u3066\u3044\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-115\">\n<h2 class=\"wp-block-heading\" id=\"i-25\">6. \u307e\u3068\u3081\uff1aJava Optional\u3067\u5b9f\u73fe\u3059\u308b\u3001\u3088\u308a\u5b89\u5168\u3067\u7f8e\u3057\u3044\u30b3\u30fc\u30c9\u306e\u4e16\u754c<\/h2>\n<\/div>\n\n<div id=\"sgb-css-id-116\">\n<p>Java Optional\u306f\u3001null\u306e\u53d6\u308a\u6271\u3044\u306b\u95a2\u3059\u308b\u591a\u304f\u306e\u554f\u984c\u3092\u89e3\u6c7a\u3057\u3001\u3088\u308a\u5b89\u5168\u3067\u7f8e\u3057\u3044\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u305f\u3081\u306e\u5f37\u529b\u306a\u30c4\u30fc\u30eb\u3067\u3059\u3002\u3053\u306e\u8a18\u4e8b\u3092\u901a\u3058\u3066\u898b\u3066\u304d\u305f\u3088\u3046\u306b\u3001Optional\u306e\u9069\u5207\u306a\u4f7f\u7528\u306f\u591a\u304f\u306e\u30e1\u30ea\u30c3\u30c8\u3092\u3082\u305f\u3089\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-117\">\n<h3 class=\"wp-block-heading\" id=\"i-26\">6.1 Optional\u304c\u3082\u305f\u3089\u30595\u3064\u306e\u30e1\u30ea\u30c3\u30c8\uff1a\u518d\u78ba\u8a8d<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-122\">\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:#009EF3;color:#FFF\" class=\"sgb-box-simple__title\">Optional \u306e\u30e1\u30ea\u30c3\u30c8<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:#009EF3;background-color:#FFF\">\n<ol class=\"wp-block-list\"><div id=\"sgb-css-id-118\">\n<li><strong>NullPointerException\u306e\u30ea\u30b9\u30af\u8efd\u6e1b<\/strong>\uff1a \u5024\u306e\u5b58\u5728\u78ba\u8a8d\u304c\u5f37\u5236\u3055\u308c\u308b\u305f\u3081\u3001\u4e0d\u6ce8\u610f\u306b\u3088\u308bNPE\u3092\u9632\u3050\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-119\">\n<li><strong>\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u5411\u4e0a<\/strong>\uff1a null\u30c1\u30a7\u30c3\u30af\u306e\u6761\u4ef6\u5206\u5c90\u304c\u6e1b\u308a\u3001\u30e1\u30bd\u30c3\u30c9\u30c1\u30a7\u30fc\u30f3\u3067\u306e\u7c21\u6f54\u306a\u8a18\u8ff0\u304c\u53ef\u80fd\u306b\u306a\u308a\u307e\u3059\u3002<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-120\">\n<li><strong>API\u8a2d\u8a08\u306e\u6539\u5584<\/strong>\uff1a \u30e1\u30bd\u30c3\u30c9\u306e\u623b\u308a\u5024\u3068\u3057\u3066\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u547c\u3073\u51fa\u3057\u5143\u306b\u5024\u306e\u4e0d\u5728\u306e\u53ef\u80fd\u6027\u3092\u660e\u793a\u3067\u304d\u307e\u3059\u3002<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-121\">\n<li><strong>\u95a2\u6570\u578b\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u3068\u306e\u89aa\u548c\u6027<\/strong>\uff1a map()\u3084flatMap()\u306a\u3069\u306e\u64cd\u4f5c\u306b\u3088\u308a\u3001\u95a2\u6570\u578b\u30b9\u30bf\u30a4\u30eb\u306e\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u304c\u5bb9\u6613\u306b\u306a\u308a\u307e\u3059\u3002<\/li>\n<\/div>\n\n\n<li><strong>\u30c6\u30b9\u30c8\u306e\u5bb9\u6613\u6027<\/strong>\uff1a Optional\u3092\u4f7f\u7528\u3057\u305f\u30b3\u30fc\u30c9\u306f\u3001\u3088\u308a\u660e\u78ba\u306a\u72b6\u614b\u3092\u6301\u3064\u305f\u3081\u3001\u30e6\u30cb\u30c3\u30c8\u30c6\u30b9\u30c8\u304c\u66f8\u304d\u3084\u3059\u304f\u306a\u308a\u307e\u3059\u3002<\/li>\n<\/ol>\n<\/div><\/div>\n<\/div>\n\n<div id=\"sgb-css-id-123\">\n<p>\u3053\u308c\u3089\u306e\u30e1\u30ea\u30c3\u30c8\u306f\u3001\u500b\u3005\u306e\u958b\u767a\u8005\u306e\u751f\u7523\u6027\u3092\u5411\u4e0a\u3055\u305b\u308b\u3060\u3051\u3067\u306a\u304f\u3001\u30c1\u30fc\u30e0\u5168\u4f53\u306e\u30b3\u30fc\u30c9\u54c1\u8cea\u3068\u4fdd\u5b88\u6027\u3092\u5927\u5e45\u306b\u6539\u5584\u3057\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-124\">\n<h3 class=\"wp-block-heading\" id=\"i-27\">6.2 \u4eca\u5f8c\u306eJava\u958b\u767a\uff1aOptional\u3092\u6d3b\u7528\u3057\u305f\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u6a19\u6e96\u306e\u78ba\u7acb<\/h3>\n<\/div>\n\n<div id=\"sgb-css-id-125\">\n<p>Optional\u306e\u52b9\u679c\u7684\u306a\u6d3b\u7528\u306f\u3001\u4eca\u5f8c\u306eJava\u958b\u767a\u306b\u304a\u3044\u3066\u91cd\u8981\u306a\u5f79\u5272\u3092\u679c\u305f\u3059\u3067\u3057\u3087\u3046\u3002\u4ee5\u4e0b\u306e\u30a2\u30d7\u30ed\u30fc\u30c1\u3092\u691c\u8a0e\u3059\u308b\u3053\u3068\u3067\u3001\u30c1\u30fc\u30e0\u5168\u4f53\u3067Optional\u306e\u6069\u6075\u3092\u6700\u5927\u9650\u306b\u53d7\u3051\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-128\">\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">\u52b9\u679c\u7684\u306a\u6d3b\u7528\u3078\u306e\u30a2\u30d7\u30ed\u30fc\u30c1<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ol class=\"wp-block-list\"><div id=\"sgb-css-id-126\">\n<li>\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u30ac\u30a4\u30c9\u30e9\u30a4\u30f3\u306bOptional\u306e\u4f7f\u7528\u898f\u5247\u3092\u542b\u3081\u308b<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-127\">\n<li>\u30b3\u30fc\u30c9\u30ec\u30d3\u30e5\u30fc\u3067Optional\u306e\u9069\u5207\u306a\u4f7f\u7528\u3092\u78ba\u8a8d\u3059\u308b<\/li>\n<\/div>\n\n\n<li>\u30c1\u30fc\u30e0\u5168\u4f53\u3067Optional\u306e\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\u3092\u5171\u6709\u3059\u308b<\/li>\n<\/ol>\n<\/div><\/div>\n<\/div>\n\n<div id=\"sgb-css-id-129\">\n<p>\u5c06\u6765\u7684\u306b\u306f\u3001Java\u306e\u9032\u5316\u3068\u3068\u3082\u306bOptional\u3082\u3055\u3089\u306b\u6539\u5584\u3055\u308c\u308b\u53ef\u80fd\u6027\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<\/div>\n\n<div id=\"sgb-css-id-132\">\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">\u4eca\u5f8c\u306e\u6539\u5584\u306e\u53ef\u80fd\u6027<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-130\">\n<li>Optional\u306e\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u6700\u9069\u5316<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-131\">\n<li>\u3088\u308a\u76f4\u611f\u7684\u306aAPI\u306e\u8ffd\u52a0<\/li>\n<\/div>\n\n\n<li>\u4ed6\u306e\u8a00\u8a9e\u6a5f\u80fd\uff08\u4f8b\uff1a\u30d1\u30bf\u30fc\u30f3\u30de\u30c3\u30c1\u30f3\u30b0\uff09\u3068\u306e\u7d71\u5408<\/li>\n<\/ul>\n<\/div><\/div>\n<\/div>\n\n<div id=\"sgb-css-id-133\">\n<p>\u307e\u305f\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306a\u6539\u5584\u70b9\u3082\u671f\u5f85\u3055\u308c\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n<div class=\"wp-block-sgb-block-simple sgb-box-simple sgb-box-simple--title-normal sgb-box-simple--with-border\"><div style=\"background-color:var(--wp--preset--color--sango-main);color:#FFF\" class=\"sgb-box-simple__title\">\u671f\u5f85\u3055\u308c\u308b\u6539\u5584\u70b9<\/div><div class=\"sgb-box-simple__body\" style=\"border-color:var(--wp--preset--color--sango-main);background-color:#FFF\">\n<ul class=\"wp-block-list\"><div id=\"sgb-css-id-134\">\n<li>\u30b7\u30ea\u30a2\u30e9\u30a4\u30ba\u53ef\u80fd\u306aOptional\u306e\u5c0e\u5165<\/li>\n<\/div>\n\n<div id=\"sgb-css-id-135\">\n<li>\u30d7\u30ea\u30df\u30c6\u30a3\u30d6\u578b\u306eOptional\u3068\u306e\u7d71\u5408<\/li>\n<\/div>\n\n\n<li>Optional\u306e\u30b9\u30c8\u30ea\u30fc\u30e0\u64cd\u4f5c\u306e\u3055\u3089\u306a\u308b\u62e1\u5f35<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n<div id=\"sgb-css-id-136\">\n<p>Optional\u306f\u3001null\u306e\u4e0d\u5b89\u304b\u3089\u958b\u767a\u8005\u3092\u89e3\u653e\u3057\u3001\u3088\u308a\u8868\u73fe\u529b\u8c4a\u304b\u3067\u5b89\u5168\u306a\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u305f\u3081\u306e\u5f37\u529b\u306a\u30c4\u30fc\u30eb\u3067\u3059\u3002\u3053\u306e\u8a18\u4e8b\u3067\u5b66\u3093\u3060\u30c6\u30af\u30cb\u30c3\u30af\u3068\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\u3092\u65e5\u3005\u306e\u958b\u767a\u306b\u53d6\u308a\u5165\u308c\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u5805\u7262\u3067\u4fdd\u5b88\u6027\u306e\u9ad8\u3044Java\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3092\u69cb\u7bc9\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u3067\u3057\u3087\u3046\u3002<\/p>\n<\/div>\n\n\n<p>Optional\u3092\u6d3b\u7528\u3057\u3001null\u306e\u4e0d\u5b89\u306e\u306a\u3044\u3001\u7f8e\u3057\u3044\u30b3\u30fc\u30c9\u306e\u4e16\u754c\u3078\u8e0f\u307f\u51fa\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Warning: Undefined array key &#8220;is_admin&#8221; in \/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/ &#8230; <\/p>\n","protected":false},"author":1,"featured_media":3044,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,74,66],"tags":[],"class_list":{"0":"post-341","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-java","8":"category-java-error-handling","9":"category-java-syntax"},"_links":{"self":[{"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/posts\/341","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=341"}],"version-history":[{"count":1,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/posts\/341\/revisions"}],"predecessor-version":[{"id":342,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/posts\/341\/revisions\/342"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/media\/3044"}],"wp:attachment":[{"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=341"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=341"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=341"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}