{"@attributes":{"version":"2.0"},"channel":{"title":"Optional on \u9694\u53f6\u9ec4\u83ba Yanbin's Blog - \u8f6f\u4ef6\u7f16\u7a0b\u5b9e\u8df5","link":"https:\/\/yanbin.blog\/tags\/optional\/","description":"Recent content in Optional on \u9694\u53f6\u9ec4\u83ba Yanbin's Blog - \u8f6f\u4ef6\u7f16\u7a0b\u5b9e\u8df5","generator":"Hugo -- gohugo.io","language":"en-us","managingEditor":"yabqiu@gmail.com (Yanbin Qiu)","webMaster":"yabqiu@gmail.com (Yanbin Qiu)","copyright":"Yanbin \u9694\u53f6\u9ec4\u83ba","lastBuildDate":"Sun, 22 Jul 2018 23:23:45 -0500","item":[{"title":"Java8 Optional \u51e0\u4e2a\u5e38\u89c1\u9519\u8bef\u7528\u6cd5","link":"https:\/\/yanbin.blog\/java8-optional-several-common-incorrect-usages\/","pubDate":"Sun, 22 Jul 2018 23:23:45 -0500","author":"yabqiu@gmail.com (Yanbin Qiu)","guid":"https:\/\/yanbin.blog\/java8-optional-several-common-incorrect-usages\/","description":"\n

Java 8\u00a0\u5f15\u5165\u7684 Optional\u00a0\u7c7b\u578b\uff0c\u57fa\u672c\u662f\u628a\u5b83\u5f53\u4f5c null\u00a0\u503c\u4f18\u96c5\u7684\u5904\u7406\u65b9\u5f0f\u3002\u5176\u5b9e\u4e5f\u4e0d\u5b8c\u5168\u5982\u6b64\uff0cOptional\u00a0\u5728\u8bed\u4e49\u4e0a\u66f4\u80fd\u4f53\u73b0\u6709\u8fd8\u662f\u6ca1\u6709\u503c\u3002\u6240\u4ee5\u5b83\u4e0d\u662f\u8bbe\u8ba1\u6765\u4f5c\u4e3a null\u00a0\u7684\u66ff\u4ee3\u54c1\uff0c\u5982\u679c\u65b9\u6cd5\u8fd4\u56de null\u00a0\u503c\u8868\u8fbe\u4e86\u4e8c\u4e49\u6027\uff0c\u6ca1\u6709\u7ed3\u679c\u6216\u662f\u6267\u884c\u4e2d\u51fa\u73b0\u5f02\u5e38\u3002<\/p>\n

\u5728 Oracle\u00a0 \u505a\u00a0 Java\u00a0\u8bed\u8a00\u5de5\u4f5c\u7684\u00a0 Brian\u00a0Goetz\u00a0\u5728 Stack Overflow\u00a0\u56de\u590d\u00a0 Should Java 8 getters return optional type?<\/a>\u00a0\u4e2d\u8bb2\u8ff0\u4e86\u5f15\u5165\u00a0 Optional\u00a0\u7684\u4e3b\u8981\u52a8\u673a\u3002<\/p>\n

\nOur intention was to provide a limited mechanism for library method return types where there needed to be a clear way to represent \u201cno result\u201d, and using null for such was overwhelmingly likely to cause errors.\n<\/blockquote>\n

\u8bf4\u7684\u662f\u00a0 Optional\u00a0\u63d0\u4f9b\u4e86\u4e00\u4e2a\u6709\u9650\u7684\u673a\u5236\u8ba9\u7c7b\u5e93\u65b9\u6cd5\u8fd4\u56de\u503c\u6e05\u6670\u7684\u8868\u8fbe\u6709\u4e0e\u6ca1\u6709\u503c\uff0c\u907f\u514d\u5f88\u591a\u65f6\u5019 null\u00a0\u9020\u6210\u7684\u9519\u8bef\u3002\u5e76\u975e\u6709\u4e86\u00a0 Optional\u00a0\u5c31\u8981\u5b8c\u5168\u675c\u7edd NullPointerException\u3002<\/p>\n

\u5728\u00a0Java 8\u00a0\u4e4b\u524d\u4e00\u4e2a\u5b9e\u8df5\u662f\u65b9\u6cd5\u8fd4\u56de\u96c6\u5408\u6216\u6570\u7ec4\u65f6\uff0c\u5e94\u8fd4\u56de\u7a7a\u96c6\u5408\u6216\u6570\u7ec4\u8868\u793a\u6ca1\u6709\u5143\u7d20;\u00a0\u800c\u5bf9\u4e8e\u8fd4\u56de\u5bf9\u8c61\uff0c\u53ea\u80fd\u7528\u00a0null\u00a0\u6765\u8868\u793a\u4e0d\u5b58\u5728\uff0c\u73b0\u5728\u53ef\u4ee5\u7528\u00a0 Optional\u00a0\u6765\u8868\u793a\u8fd9\u4e2a\u610f\u4e49\u3002<\/p>\n

\u81ea Java8\u00a0\u4e8e\u00a0 2014-03-18\u00a0\u53d1\u5e03\u540e\u5df2 5\u00a0\u5e74\u6709\u4f59\uff0c\u8fd9\u91cc\u5c31\u5217\u4e3e\u51e0\u4e2a\u6211\u4eec\u5728\u9879\u76ee\u5b9e\u8df5\u4e2d\u4f7f\u7528\u00a0Optional\u00a0\u5e38\u89c1\u7684\u51e0\u4e2a\u7528\u6cd5\u3002<\/p>\n

Optional\u00a0\u7c7b\u578b\u4f5c\u4e3a\u5b57\u6bb5\u6216\u65b9\u6cd5\u53c2\u6570<\/h3>\n

\u8fd9\u513f\u628a Optional\u00a0 \u7c7b\u578b\u7528\u4e3a\u5b57\u6bb5(\u7c7b\u6216\u5b9e\u4f8b\u53d8\u91cf)\u548c\u65b9\u6cd5\u53c2\u6570\u653e\u5728\u4e00\u8d77\u6765\u8bb2\uff0c\u662f\u56e0\u4e3a\u5047\u5982\u6211\u4eec\u4f7f\u7528 IntelliJ IDEA\u00a0\u6765\u5199\u00a0Java 8\u00a0\u4ee3\u7801\uff0cIDEA\u00a0\u5bf9\u4e8e\u00a0 Optional\u00a0\u4f5c\u4e3a\u5b57\u6bb5\u548c\u65b9\u6cd5\u53c2\u6570\u4f1a\u7ed9\u51fa\u540c\u6837\u7684\u4ee3\u7801\u5efa\u8bae\uff1a"},{"title":"\u4f7f\u7528 Java8 Optional \u7684\u6b63\u786e\u59ff\u52bf","link":"https:\/\/yanbin.blog\/proper-ways-of-using-java8-optional\/","pubDate":"Mon, 05 Sep 2016 01:52:54 -0500","author":"yabqiu@gmail.com (Yanbin Qiu)","guid":"https:\/\/yanbin.blog\/proper-ways-of-using-java8-optional\/","description":"\n\u6211\u4eec\u77e5\u9053 Java 8 \u589e\u52a0\u4e86\u4e00\u4e9b\u5f88\u6709\u7528\u7684 API, \u5176\u4e2d\u4e00\u4e2a\u5c31\u662f Optional. \u5982\u679c\u5bf9\u5b83\u4e0d\u7a0d\u5047\u63a2\u7d22, \u53ea\u662f\u8f7b\u63cf\u6de1\u5199\u7684\u8ba4\u4e3a\u5b83\u53ef\u4ee5\u4f18\u96c5\u7684\u89e3\u51b3 NullPointException \u7684\u95ee\u9898, \u4e8e\u662f\u4ee3\u7801\u5c31\u5f00\u59cb\u8fd9\u4e48\u5199\u4e86\n

1<\/span>Optional<\/span><<\/span>User<\/span>><\/span> <\/span>user<\/span> <\/span>=<\/span> <\/span>......<\/span>\n<\/span><\/span><\/span>2<\/span>if<\/span> <\/span>(<\/span>user<\/span>.<\/span>isPresent<\/span>())<\/span> <\/span>{<\/span>\n<\/span><\/span><\/span>3<\/span> <\/span>return<\/span> <\/span>user<\/span>.<\/span>getOrders<\/span>();<\/span>\n<\/span><\/span><\/span>4<\/span>}<\/span> <\/span>else<\/span> <\/span>{<\/span>\n<\/span><\/span><\/span>5<\/span> <\/span>return<\/span> <\/span>Collections<\/span>.<\/span>emptyList<\/span>();<\/span>\n<\/span><\/span><\/span>6<\/span>}<\/span><\/span><\/span><\/code><\/pre><\/div>\n\u90a3\u4e48\u4e0d\u5f97\u4e0d\u8bf4\u6211\u4eec\u7684\u601d\u7ef4\u4ecd\u7136\u662f\u5728\u539f\u5730\u8e0f\u6b65, \u53ea\u662f\u672c\u80fd\u7684\u8ba4\u4e3a\u5b83\u4e0d\u8fc7\u662f User \u5b9e\u4f8b\u7684\u5305\u88c5, \u8fd9\u4e0e\u6211\u4eec\u4e4b\u524d\u5199\u6210\n
1<\/span>User<\/span> <\/span>user<\/span> <\/span>=<\/span> <\/span>.....<\/span>\n<\/span><\/span><\/span>2<\/span>if<\/span> <\/span>(<\/span>user<\/span> <\/span>!=<\/span> <\/span>null<\/span>)<\/span> <\/span>{<\/span>\n<\/span><\/span><\/span>3<\/span> <\/span>return<\/span> <\/span>user<\/span>.<\/span>getOrders<\/span>();<\/span>\n<\/span><\/span><\/span>4<\/span>}<\/span> <\/span>else<\/span> <\/span>{<\/span>\n<\/span><\/span><\/span>5<\/span> <\/span>return<\/span> <\/span>Collections<\/span>.<\/span>emptyList<\/span>();<\/span>\n<\/span><\/span><\/span>6<\/span>}<\/span><\/span><\/span><\/code><\/pre><\/div>\n\u5b9e\u8d28\u4e0a\u662f\u6ca1\u6709\u4efb\u4f55\u5206\u522b. \u8fd9\u5c31\u662f\u6211\u4eec\u5c06\u8981\u8bb2\u5230\u7684\u4f7f\u7528\u597d Java 8 Optional \u7c7b\u578b\u7684\u6b63\u786e\u59ff\u52bf.\n\u5728\u91cc\u7ea6\u5965\u8fd0\u4e4b\u65f6, \u65b0\u95fb\u4e00\u518d\u63d0\u8d77\u4e94\u661f\u7ea2\u65d7\u6709\u95ee\u9898, \u53ef\u662f\u6211\u600e\u4e48\u770b\u90fd\u770b\u4e0d\u51fa\u6765\u6709\u4ec0\u4e48\u95ee\u9898, \u540e\u6765\u624d\u9053\u662f\u5c0f\u661f\u661f\u819c\u62dc\u4e2d\u592e\u7684\u59ff\u52bf\u4e0d\u5bf9. \u56e0\u6b64\u6211\u4eec\u5343\u4e07\u4e5f\u522b\u5bf9\u81ea\u5df1\u4e60\u4ee5\u4e3a\u5e38\u7684\u4e8b\u60c5\u89c9\u5f97\u7406\u6240\u5f53\u7136, \u4e1d\u6beb\u4e0d\u4f1a\u89c9\u5f97\u6709\u4f55\u4e0d\u59a5, \u6362\u53e5\u8bdd\u8bf4\u4e5f\u5c31\u662f\u5f53\u6211\u4eec\u5207\u6362\u5230 Java 8 \u7684 Optional \u65f6, \u4e0d\u80fd\u7ee7\u627f\u6027\u7684\u5bf9\u5f85\u8fc7\u5f80 null \u65f6\u7684\u90a3\u79cd\u601d\u7ef4, \u5e94\u8be5\u638c\u63e1\u597d\u65b0\u7684, \u6b63\u786e\u7684\u4f7f\u7528 Java 8 Optional \u7684\u6b63\u786e\u59ff\u52bf."}]}}