{"id":10008300,"date":"2023-09-20T20:38:07","date_gmt":"2023-09-20T12:38:07","guid":{"rendered":"https:\/\/blog.itmax.cn\/?p=10008300"},"modified":"2023-09-20T20:38:07","modified_gmt":"2023-09-20T12:38:07","slug":"java-21-%e6%96%b0%e7%89%b9%e6%80%a7%ef%bc%9aswitch%e7%9a%84%e6%a8%a1%e5%bc%8f%e5%8c%b9%e9%85%8d","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10008300","title":{"rendered":"Java 21 \u65b0\u7279\u6027\uff1aswitch\u7684\u6a21\u5f0f\u5339\u914d"},"content":{"rendered":"

\u5728\u4e4b\u524d\u7684Java 17\u65b0\u7279\u6027\u4e2d\uff0c\u6211\u4eec\u4ecb\u7ecd\u8fc7\u5173\u4e8eJEP 406: switch\u7684\u6a21\u5f0f\u5339\u914d<\/a>\uff0c\u4f46\u5f53\u65f6\u8fd8\u53ea\u662f\u5173\u4e8e\u6b64\u5185\u5bb9\u7684\u9996\u4e2a\u9884\u89c8\u7248\u672c\u3002\u4e4b\u540e\u5728JDK 18\u3001JDK 19\u3001JDK 20\u4e2d\u53c8\u90fd\u8fdb\u884c\u4e86\u66f4\u65b0\u548c\u5b8c\u5584\u3002\u5982\u4eca\uff0c\u5728JDK 21\u4e2d\uff0c\u8be5\u7279\u6027\u5f97\u5230\u4e86\u6700\u7ec8\u786e\u5b9a\uff01\u4e0b\u9762\uff0c\u6211\u4eec\u5c31\u518d\u6b63\u5f0f\u5b66\u4e60\u4e00\u4e0b\u8be5\u529f\u80fd\uff01<\/p>\n

\u5728\u4ee5\u5f80\u7684switch\u8bed\u53e5\u4e2d\uff0c\u5bf9\u4e8ecase<\/code>\u4e2d\u7684\u7c7b\u578b\u5339\u914d\u9650\u5236\u662f\u5f88\u591a\u7684\u3002\u6bd4\u5982\u4e0b\u9762\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\u7684Map<\/code>\u4e2d\u53ef\u80fd\u5b58\u50a8\u4e86\u4e0d\u540c\u7c7b\u578b\u7684\u5bf9\u8c61\uff0c\u6211\u4eec\u8981\u5224\u65ad\u7684\u65f6\u5019\uff0c\u5c31\u53ea\u80fd\u4f9d\u9760if-else<\/code>\u6765\u5b8c\u6210\u3002<\/p>\n

Map<String, Object> data = new HashMap<>();\ndata.put("key1", "aaa");\ndata.put("key2", 111);\nif (data.get("key1") instanceof String s) {\n  log.info(s);\n}\n\nif (data.get("key") instanceof String s) {\n  log.info(s);\n} else if (data.get("key") instanceof Double s) {\n  log.info(s);\n} else if (data.get("key") instanceof Integer s) {\n  log.info(s);\n}<\/code><\/pre>\n
\u73b0\u5728\u5f00\u59cb\uff0c\u8fd9\u6837\u7684\u7c7b\u578b\u5224\u65ad\u5173\u7cfb\uff0c\u5c31\u53ef\u4ee5\u7b80\u5316\u4e3a\u5982\u4e0b\u7684switch<\/code>\u4ee3\u7801\uff1a<\/p>\n
switch (data.get("key1")) {\n  case String s  -> log.info(s);\n  case Double d  -> log.info(d.toString());\n  case Integer i -> log.info(i.toString());\n  default        -> log.info("");\n}<\/code><\/pre>\n
\u8fd9\u4e2a\u529f\u80fd\u8fd8\u662f\u975e\u5e38\u6709\u7528\u7684\uff0c\u5c24\u5176\u662f\u5b58\u5728\u4e00\u4e9b\u62bd\u8c61\u5c01\u88c5\u7684\u65f6\u5019\uff0c\u53ef\u80fd\u5b58\u5728\u4e00\u4e9b\u7236\u5b50\u3001\u5144\u5f1f\u7b49\u5173\u7cfb\u7c7b\u7684\u65f6\u5019\uff0c\u4e3a\u4e86\u5224\u65ad\u662f\u4ec0\u4e48\u7c7b\u578b\uff0c\u5c31\u4e0d\u7528\u5199\u5f88\u591aif\u6765\u5904\u7406\u4e86\uff0c\u4ee3\u7801\u7b80\u6d01\u5ea6\u53ef\u4ee5\u5f97\u5230\u8fdb\u4e00\u6b65\u7684\u4f18\u5316\u3002<\/p>\n
\u5bf9\u4e8e\u4e0a\u9762\u7684\u4f8b\u5b50\uff0c\u8fd8\u6ca1\u6709\u5347\u7ea7\u5230Java 17\u7684\u7528\u6237\uff0c\u8fd8\u6d89\u53ca\u4e24\u4e2a\u4e2d\u95f4\u77e5\u8bc6\u70b9\uff0c\u5efa\u8bae\u53ef\u4ee5\u8865\u5145\u5b66\u4e60\u4e00\u4e0b\uff1a\u7b2c\u4e00\u4e2a\u662fJava 16\u4e2d\u7684instance of\u589e\u5f3a<\/a>\uff1b\u7b2c\u4e8c\u4e2a\u662fswitch\u4e2d\u4f7f\u7528Lambda\u7684\u589e\u5f3a<\/a>\u3002<\/p><\/blockquote>\n
\u5982\u679c\u60a8\u5b66\u4e60\u8fc7\u7a0b\u4e2d\u5982\u9047\u56f0\u96be\uff1f\u53ef\u4ee5\u52a0\u5165\u6211\u4eec\u8d85\u9ad8\u8d28\u91cf\u7684\u6280\u672f\u4ea4\u6d41\u7fa4<\/a>\uff0c\u53c2\u4e0e\u4ea4\u6d41\u4e0e\u8ba8\u8bba\uff0c\u66f4\u597d\u7684\u5b66\u4e60\u4e0e\u8fdb\u6b65\uff01<\/p>\n
\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u516c\u4f17\u53f7\uff1a\u7a0b\u5e8f\u733fDD\u3002\u7b2c\u4e00\u65f6\u95f4\u4e86\u89e3\u524d\u6cbf\u884c\u4e1a\u6d88\u606f\u3001\u5206\u4eab\u6df1\u5ea6\u6280\u672f\u5e72\u8d27\u3001\u83b7\u53d6\u4f18\u8d28\u5b66\u4e60\u8d44\u6e90<\/p><\/blockquote>\n
https:\/\/segmentfault.com\/a\/1190000044235089<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
\u5728\u4e4b\u524d\u7684Java 17\u65b0\u7279\u6027\u4e2d\uff0c\u6211\u4eec\u4ecb\u7ecd\u8fc7\u5173\u4e8eJEP 406: switch\u7684\u6a21\u5f0f\u5339\u914d\uff0c\u4f46\u5f53\u65f6\u8fd8\u53ea\u662f\u5173\u4e8e\u6b64\u5185\u5bb9 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-10008300","post","type-post","status-publish","format-standard","hentry","category-share"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10008300","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10008300"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10008300\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10008300"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10008300"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10008300"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}