{"id":31387,"date":"2023-05-23T02:13:13","date_gmt":"2023-09-29T02:38:26","guid":{"rendered":"https:\/\/www.silicloud.com\/zh\/blog\/%e3%80%90%e5%a4%87%e5%bf%98%e5%bd%95%e3%80%91%e5%85%b3%e4%ba%8ejava%e7%9a%84optional\/"},"modified":"2025-08-12T23:47:02","modified_gmt":"2025-08-12T15:47:02","slug":"%e3%80%90%e5%a4%87%e5%bf%98%e5%bd%95%e3%80%91%e5%85%b3%e4%ba%8ejava%e7%9a%84optional","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/zh\/blog\/%e3%80%90%e5%a4%87%e5%bf%98%e5%bd%95%e3%80%91%e5%85%b3%e4%ba%8ejava%e7%9a%84optional\/","title":{"rendered":"\u3010\u5907\u5fd8\u5f55\u3011\u5173\u4e8eJava\u7684Optional"},"content":{"rendered":"

\u9996\u5148<\/h1>\n

\u5173\u4e8eOptional\uff0c\u6211\u5c06\u4ee5\u6211\u81ea\u5df1\u7684\u7406\u89e3\u5199\u4e0b\u5907\u5fd8\u5f55\u3002<\/p>\n

“Optional” \u5728\u4e2d\u6587\u4e2d\u662f\u4ec0\u4e48\u610f\u601d\uff1f<\/h1>\n

\u4e00\u79cd\u7528\u6765\u5c01\u88c5\u503c\u5e76\u8868\u8fbe\u8be5\u503c\u53ef\u80fd\u4e3anull\u7684\u7c7b\uff0c\u53ef\u4ee5\u9632\u6b62NullPointerException\u3002<\/p>\n

\u4f7f\u7528\u53ef\u9009\u9879\u7684\u539f\u56e0<\/h1>\n

\u8c03\u7528\u53ef\u80fd\u4e3anull\u7684\u65b9\u6cd5\u65f6\uff0c\u9700\u8981\u4e8b\u5148\u5b9e\u65bd\u68c0\u67e5\u662f\u5426\u4e3anull\u3002
\n\u7136\u800c\uff0c\u6709\u53ef\u80fd\u5fd8\u8bb0\u5b9e\u65bd\u68c0\u67e5\u3002
\n\u4e3a\u4e86\u9632\u6b62\u9057\u5fd8\u5b9e\u65bd\uff0c\u53ef\u4ee5\u4f7f\u7528Optional\u3002<\/p>\n

\u8bf7\u901a\u8fc7\u6e90\u4ee3\u7801\u786e\u8ba4<\/h1>\n

\u4f7f\u7528ofNullable\u65b9\u6cd5\uff0c\u521b\u5efaOptional\u7c7b\u578b\u7684\u5bf9\u8c61\u3002
\n\u5728if\u8bed\u53e5\u4e2d\u4f7f\u7528isPresent\u51fd\u6570\uff0c\u4ec5\u5f53\u503c\u5b58\u5728\u65f6\u624d\u6267\u884clength\u65b9\u6cd5\u3002
\n\u6b64\u65f6\uff0c\u7531\u4e8e\u53d8\u91cfstr\u7684\u503c\u4e3anull\uff0c\u56e0\u6b64\u4e0d\u4f1a\u5728\u63a7\u5236\u53f0\u4e0a\u663e\u793a\u4efb\u4f55\u5185\u5bb9\u3002<\/p>\n

        String<\/span> str<\/span>=<\/span>null<\/span>;<\/span>\r\n        Optional<\/span><<\/span>String<\/span>><\/span>strOpt<\/span>=<\/span>Optional<\/span>.<\/span>ofNullable<\/span>(<\/span>str<\/span>);<\/span>\r\n\r\n        if<\/span>(<\/span>strOpt<\/span>.<\/span>isPresent<\/span>())<\/span> {<\/span>\r\n            String<\/span> message<\/span>=<\/span>strOpt<\/span>.<\/span>get<\/span>();<\/span>\r\n            System<\/span>.<\/span>out<\/span>.<\/span>println<\/span>(<\/span>message<\/span>.<\/span>length<\/span>());<\/span>\r\n        }<\/span>\r\n<\/code><\/pre>\n
\u4e0d\u4f7f\u7528if\u8bed\u53e5\u8fdb\u884cNull\u68c0\u67e5\u7684\u65b9\u6cd5\u8fd8\u53ef\u4ee5\u4f7f\u7528Lambda\u8868\u8fbe\u5f0f\u6765\u7f16\u5199\u5982\u4e0b\u3002<\/p>\n
        strOpt<\/span>.<\/span>ifPresent<\/span>(<\/span>v<\/span>-><\/span>System<\/span>.<\/span>out<\/span>.<\/span>println<\/span>(<\/span>v<\/span>.<\/span>length<\/span>()));<\/span>\r\n<\/code><\/pre>\n
\u5982\u679c\u4f5c\u4e3a\u503c\u63a5\u53d7\u7684\u60c5\u51b5<\/h1>\n
\u4f7f\u7528map\u51fd\u6570\u3002
\nmap\u65b9\u6cd5\u7684\u8fd4\u56de\u503c\u662f\u5305\u88c5\u4e86lambda\u8868\u8fbe\u5f0f\u8fd4\u56de\u503c\u7684Optional\u3002\uff08\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u8fd4\u56de\u7684\u662fInteger\u7c7b\u578b\u7684Optional\uff09
\n\u5982\u679cstrOpt\u7684\u503c\u4e0d\u5b58\u5728\uff0c\u5219\u4f1a\u8fd4\u56de\u6ca1\u6709\u503c\u7684Optional\u5bf9\u8c61\u3002<\/p>\n
Optional<\/span><<\/span>String<\/span>><\/span>strOpt<\/span>=<\/span>Optional<\/span>.<\/span>ofNullable<\/span>(<\/span>str<\/span>);<\/span>\r\nOptional<\/span><<\/span>Integer<\/span>><\/span>lengthOpt<\/span>=<\/span>strOpt<\/span>.<\/span>map<\/span>(<\/span>v<\/span>-><\/span>v<\/span>.<\/span>length<\/span>());<\/span>\r\n<\/code><\/pre>\n
\u8bf7\u9605\u8bfb\u4e0b\u5217\u5185\u5bb9\u5e76\u7528\u4e2d\u6587\u8fdb\u884c\u540c\u4e49\u6539\u5199\uff0c\u53ea\u9700\u8981\u63d0\u4f9b\u4e00\u4e2a\u9009\u9879\uff1a\u53c2\u8003<\/h1>\n","protected":false},"excerpt":{"rendered":"
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