{"id":1453,"date":"2022-11-05T17:09:13","date_gmt":"2022-11-05T09:09:13","guid":{"rendered":"https:\/\/qaqaq.top\/?p=1453"},"modified":"2022-11-27T12:39:44","modified_gmt":"2022-11-27T04:39:44","slug":"%e5%a4%8d%e4%b9%a0%ef%bc%9aoptional%e7%b1%bb%e7%9a%84%e4%bd%bf%e7%94%a8","status":"publish","type":"post","link":"https:\/\/qaqaq.top\/?p=1453","title":{"rendered":"\u590d\u4e60\uff1aOptional\u7c7b\u7684\u4f7f\u7528"},"content":{"rendered":"\n<pre class=\"wp-block-code\"><code>package top.qaqaq.java.P692;\r\n\r\nimport org.junit.jupiter.api.Test;\r\n\r\nimport java.util.Optional;\r\n\r\n\/**\r\n * @author RichieZhang\r\n * @create 2022-11-05 \u4e0a\u5348 9:48\r\n *\/\r\npublic class OptionalTest {\r\n\r\n    @Test\r\n    public void test1(){\r\n        \/\/empty(): \u521b\u5efa\u7684Optional\u5bf9\u8c61\u5185\u90e8\u7684value = null\r\n        Optional&lt;Object> op1 = Optional.empty();\r\n        if (!op1.isPresent()){\/\/Optional\u5c01\u88c5\u7684\u6570\u636e\u662f\u5426\u5305\u542b\u6570\u636e\r\n            System.out.println(\"\u6570\u636e\u4e3a\u7a7a\");\r\n        }\r\n        System.out.println(op1);\r\n        System.out.println(op1.isPresent());\r\n        \/\/\u5982\u679cOptional\u5c01\u88c5\u7684\u6570\u636evalue\u4e3a\u7a7a\uff0c\u5219get()\u62a5\u9519\u3002\u5426\u5219\uff0cvalue\u4e0d\u4e3a\u7a7a\u65f6\uff0c\u8fd4\u56devalue\r\n        \/\/        System.out.println(op1.get());\r\n\r\n    }\r\n\r\n    @Test\r\n    public void test2(){\r\n        String str = \"hello\";\r\n        str = null;\r\n        \/\/of(T t):\u5c01\u88c5\u6570\u636et\u751f\u6210Optional\u5bf9\u8c61\u3002\u8981\u6c42t\u975e\u7a7a\uff0c\u5426\u5219\u62a5\u9519\u3002\r\n        Optional&lt;String> op1 = Optional.of(str);\r\n        \/\/get()\u901a\u5e38\u4e0eof()\u65b9\u6cd5\u642d\u914d\u4f7f\u7528\u3002\u7528\u4e8e\u83b7\u53d6\u5185\u90e8\u7684\u5c01\u88c5\u7684\u6570\u636evalue\r\n        String str1 = op1.get();\r\n        System.out.println(str1);\r\n\r\n    }\r\n\r\n    @Test\r\n    public void test3(){\r\n        String str = \"beijing\";\r\n        str = null;\r\n        \/\/ofNullable(T t) : \u5c01\u88c5\u6570\u636et\u8d4b\u7ed9Optional\u5185\u90e8\u7684value\u3002\u4e0d\u8981\u6c42t\u975e\u7a7a\r\n        Optional&lt;String> op1 = Optional.ofNullable(str);\r\n        \/\/orElse(T t1) : \u5982\u679cOptional\u5185\u90e8\u7684value\u975e\u7a7a\uff0c\u5219\u8fd4\u56devalue\u503c\u3002\u5982\u679c\r\n        \/\/value\u4e3a\u7a7a\uff0c\u5219\u8fd4\u56det1.\r\n        String str2 = op1.orElse(\"shanghai\");\r\n\r\n        System.out.println(str2);\r\n    }\r\n}\r\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[33],"tags":[46],"class_list":["post-1453","post","type-post","status-publish","format-standard","hentry","category-java-","tag-java"],"_links":{"self":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1453"}],"collection":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1453"}],"version-history":[{"count":1,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1453\/revisions"}],"predecessor-version":[{"id":1454,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1453\/revisions\/1454"}],"wp:attachment":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1453"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1453"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1453"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}