{"id":309247,"date":"2022-12-20T04:56:59","date_gmt":"2022-12-20T03:56:59","guid":{"rendered":"https:\/\/blog.jetbrains.com\/?post_type=idea&#038;p=309247"},"modified":"2022-12-28T08:32:40","modified_gmt":"2022-12-28T07:32:40","slug":"java-19-and-intellij-idea","status":"publish","type":"idea","link":"https:\/\/blog.jetbrains.com\/zh-hans\/idea\/2022\/12\/java-19-and-intellij-idea\/","title":{"rendered":"Java 19 \u548c IntelliJ IDEA"},"content":{"rendered":"<p>Java \u6bd4\u4ee5\u5f80\u4efb\u4f55\u65f6\u5019\u90fd\u66f4\u5145\u6ee1\u6d3b\u529b\u3002 \u5b83\u66f4\u77ed\u7684\u53d1\u5e03\u8282\u594f\u8ba9\u6211\u4eec\u6bcf\u516d\u4e2a\u6708\u5c31\u53ef\u4ee5\u8bd5\u7528\u65b0\u7684\u8bed\u8a00\u6216\u5e73\u53f0\u529f\u80fd\u3002 IntelliJ IDEA \u5e2e\u52a9\u6211\u4eec\u66f4\u6d41\u7545\u5730\u53d1\u73b0\u548c\u4f7f\u7528\u8fd9\u4e9b\u65b0\u529f\u80fd\u3002<\/p>\n<p>\u5728\u8fd9\u7bc7\u535a\u6587\u4e2d\uff0c\u6211\u5c06\u53ea\u4ecb\u7ecd Java 19 \u7684\u8bed\u8a00\u529f\u80fd\uff1a<a href=\"https:\/\/openjdk.org\/jeps\/405\" target=\"_blank\" rel=\"noreferrer noopener\">\u8bb0\u5f55\u6a21\u5f0f<\/a>\u548c <a href=\"https:\/\/openjdk.org\/jeps\/427\" target=\"_blank\" rel=\"noreferrer noopener\">switch \u6a21\u5f0f\u5339\u914d\uff08\u7b2c\u4e09\u7248\u9884\u89c8\uff09<\/a>\u3002 \u6211\u7279\u610f\u907f\u5f00\u5176\u4ed6 Java 19 \u529f\u80fd\uff0c\u4f8b\u5982\u9884\u89c8 API <a href=\"https:\/\/openjdk.org\/jeps\/425\" target=\"_blank\" rel=\"noopener\">\u865a\u62df\u7ebf\u7a0b<\/a>\u3002 IntelliJ IDEA \u652f\u6301\u865a\u62df\u7ebf\u7a0b\u7684\u57fa\u672c\u8bed\u6cd5\u9ad8\u4eae\u663e\u793a\uff0c\u56e2\u961f\u6b63\u52aa\u529b\u5728<a href=\"https:\/\/youtrack.jetbrains.com\/issue\/IDEA-301409\/Support-virtual-threads-project-loom\" target=\"_blank\" rel=\"noopener\">\u8c03\u8bd5\u5668\u548c\u5206\u6790\u5668<\/a>\u4e2d\u6dfb\u52a0\u5bf9\u865a\u62df\u7ebf\u7a0b\u7684\u652f\u6301\u3002<\/p>\n<p><!-- \/wp:paragraph --><\/p>\n<p>\u8bb0\u5f55\u6a21\u5f0f\u7b80\u5316\u4e86\u5bf9\u8bb0\u5f55\u7ec4\u4ef6\u7684\u8bbf\u95ee\u3002 \u6bd4\u8f83\u8bb0\u5f55\u6a21\u5f0f\u548c\u8bb0\u5f55<i>\u6790\u6784<\/i> \u2013 \u5f53\u5b9e\u4f8b\u4e0e\u8bb0\u5f55\u7ed3\u6784\u5339\u914d\u65f6\uff0c\u5c06\u8bb0\u5f55\u7ec4\u4ef6\u7684\u503c\u63d0\u53d6\u5230\u4e00\u7ec4\u53d8\u91cf\u3002 \u8d77\u521d\uff0c\u8fd9\u4f3c\u4e4e\u5e76\u4e0d\u503c\u5f97\u4e00\u63d0\u3002 \u4f46\u662f\uff0c\u5c06\u5b83\u4e0e switch \u548c\u5bc6\u5c01\u7c7b\u7684\u6a21\u5f0f\u5339\u914d\u7b49\u5176\u4ed6\u8bed\u8a00\u529f\u80fd\u7ed3\u5408\u4f7f\u7528\u65f6\uff0c\u7ed3\u679c\u4f1a\u76f8\u5f53\u60ca\u4eba\u3002<\/p>\n<p>switch \u7684\u6a21\u5f0f\u5339\u914d\u5c06\u6a21\u5f0f\u6dfb\u52a0\u5230 switch \u8bed\u53e5\u548c switch \u8868\u8fbe\u5f0f\u4e2d\u7684 case \u6807\u7b7e\u3002 \u53ef\u4ee5\u4e0e switch \u4e00\u8d77\u4f7f\u7528\u7684\u9009\u62e9\u5668\u8868\u8fbe\u5f0f\u7684\u7c7b\u578b\u6269\u5c55\u4e3a\u4efb\u610f\u5f15\u7528\u503c\u3002 \u53e6\u5916\uff0ccase \u6807\u7b7e\u4e0d\u518d\u9650\u4e8e\u5e38\u91cf\u503c\u3002 \u5b83\u8fd8\u6709\u52a9\u4e8e\u5c06 if-else \u8bed\u53e5\u94fe\u66ff\u6362\u4e3a switch\uff0c\u63d0\u9ad8\u4ee3\u7801\u53ef\u8bfb\u6027\u3002 \u5728\u8fd9\u7bc7\u535a\u6587\u4e2d\uff0c\u6211\u5c06\u4ecb\u7ecd switch \u6a21\u5f0f\u5339\u914d\u7b2c\u4e09\u7248\u9884\u89c8\u4e2d\u5f15\u5165\u7684\u66f4\u6539\u3002<\/p>\n<p><!-- wp:image --><\/p>\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2022\/11\/Blog_Featured_image_1280x600-9.png\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><\/p>\n<p>\u6211\u4eec\u5148\u4ece\u4e3a\u4f7f\u7528 Java 19 \u529f\u80fd\u5bf9 IntelliJ IDEA \u8fdb\u884c\u914d\u7f6e\u5f00\u59cb\u3002<\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"IntelliJ_IDEA_Configuration\" class=\"ez-toc-section\"><\/span><strong>IntelliJ IDEA \u914d\u7f6e<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>IntelliJ IDEA 2022.3 \u4e2d\u63d0\u4f9b\u4e86\u5bf9 Java 19 \u7684\u652f\u6301\u3002 \u672a\u6765\u7684 IntelliJ IDEA \u7248\u672c\u5c06\u63d0\u4f9b\u66f4\u591a\u652f\u6301\u3002 \u8981\u901a\u8fc7 Java 19 \u4f7f\u7528 switch \u7684\u6a21\u5f0f\u5339\u914d\uff0c\u5148\u8f6c\u5230 <i>Project Settings | Project<\/i>\uff08\u9879\u76ee\u8bbe\u7f6e | \u9879\u76ee\uff09\uff0c\u5c06 <i>Project SDK<\/i>\uff08\u9879\u76ee SDK\uff09\u8bbe\u4e3a 19\uff0c\u7136\u540e\u5c06\u9879\u76ee\u8bed\u8a00\u7ea7\u522b\u8bbe\u7f6e\u4e3a <i>19 (Preview) \u2013 Record patterns, pattern matching for switch (third preview)<\/i>\uff1a<\/p>\n<p><!-- wp:image --><\/p>\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2022\/11\/config1.png\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><\/p>\n<p>\u60a8\u53ef\u4ee5\u4f7f\u7528\u7cfb\u7edf\u4e0a\u5df2\u7ecf\u4e0b\u8f7d\u7684\u4efb\u610f\u7248\u672c JDK\uff0c\u4e5f\u53ef\u4ee5\u70b9\u51fb <i>Edit<\/i>\uff08\u7f16\u8f91\uff09\uff0c\u7136\u540e\u9009\u62e9 <i>Add SDK &gt;<\/i>\uff08\u6dfb\u52a0 SDK\uff09\u3001<i>Download JDK\u2026<\/i>\uff08\u4e0b\u8f7d JDK\u2026\uff09\u6765\u4e0b\u8f7d\u5176\u4ed6\u7248\u672c\u3002 \u60a8\u53ef\u4ee5\u4ece\u4f9b\u5e94\u5546\u5217\u8868\u4e2d\u9009\u62e9\u8981\u4e0b\u8f7d\u7684 JDK \u7248\u672c\u3002<\/p>\n<p>\u5728 Modules\uff08\u6a21\u5757\uff09\u9009\u9879\u5361\u4e0a\uff0c\u786e\u4fdd\u4e3a\u6a21\u5757\u9009\u62e9\u76f8\u540c\u7684\u8bed\u8a00\u7ea7\u522b \u2013 <i>19 (Preview) \u2013 Record patterns, pattern matching for switch (third preview)<\/i>\uff1a<\/p>\n<p>\u00a0<\/p>\n<p><!-- wp:image --><\/p>\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2022\/11\/config2.png\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><\/p>\n<p>\u9009\u62e9\u6b64\u9009\u9879\u540e\uff0c\u53ef\u80fd\u4f1a\u51fa\u73b0\u4ee5\u4e0b\u5f39\u51fa\u7a97\u53e3\uff0c\u901a\u77e5\u60a8 IntelliJ IDEA \u53ef\u80fd\u4f1a\u5728\u540e\u7eed\u7248\u672c\u4e2d\u505c\u6b62\u5bf9 Java \u9884\u89c8\u8bed\u8a00\u529f\u80fd\u7684\u652f\u6301\u3002 \u56e0\u4e3a\u9884\u89c8\u529f\u80fd\uff08\u6682\u4e14\uff09\u4e0d\u662f\u6c38\u4e45\u6027\u7684\uff0c\u5e76\u4e14\u5b83\u53ef\u80fd\u5728\u672a\u6765\u7684 Java \u7248\u672c\u4e2d\u53d1\u751f\u53d8\u5316\uff08\u751a\u81f3\u88ab\u79fb\u9664\uff09\u3002<br \/>\u63a5\u4e0b\u6765\uff0c\u6211\u5c06\u4ecb\u7ecd\u4ec0\u4e48\u662f\u8bb0\u5f55\u6a21\u5f0f\u3001\u5b83\u7684\u597d\u5904\uff0c\u5e76\u4f7f\u7528\u5b9e\u9645\u793a\u4f8b\u6f14\u793a\u3002<\/p>\n<p><!-- wp:heading {\"level\":1} --><\/p>\n<h1><strong>\u4e3a\u4ec0\u4e48\u9700\u8981\u8bb0\u5f55\u6a21\u5f0f\uff1f<\/strong><\/h1>\n<p><!-- \/wp:heading --><\/p>\n<p>\u6570\u636e\u662f\u5927\u591a\u6570\u5e94\u7528\u7a0b\u5e8f\u7684\u6838\u5fc3\u3002 \u901a\u5e38\uff0c\u60a8\u4f7f\u7528\u7684\u5e94\u7528\u7a0b\u5e8f\u53ef\u4ee5\u4e3a\u60a8\u67e5\u627e\u6570\u636e\uff0c\u6216\u8005\u4ee5\u5e2e\u52a9\u60a8\u505a\u51fa\u51b3\u7b56\u7684\u65b9\u5f0f\u5904\u7406\u6570\u636e\u3002 \u5f53\u7136\uff0c\u5982\u679c\u5e94\u7528\u7a0b\u5e8f\u65e0\u6cd5\u5b58\u50a8\u3001\u68c0\u7d22\u6216\u5904\u7406\u5176\u6570\u636e\uff0c\u8fd9\u662f\u4e0d\u53ef\u884c\u7684\u3002<\/p>\n<p>\u5728\u6700\u8fd1\u7684\u4e00\u4e2a Java \u7248\u672c\uff08\u7b2c 16 \u7248\uff09\u4e2d\uff0c\u8bb0\u5f55\u88ab\u6dfb\u52a0\u5230 Java \u8bed\u8a00\u4e2d\uff0c\u8ba9\u5f00\u53d1\u8005\u53ef\u4ee5\u8f7b\u677e\u5904\u7406\u6570\u636e\u3002 \u8bb0\u5f55\u5927\u5e45\u7b80\u5316\u4e86\u5bf9\u4e0d\u53ef\u53d8\u6570\u636e\u5efa\u6a21\u7684\u65b9\u5f0f\u3002 \u5b83\u4eec\u5145\u5f53\u6570\u636e\u7684\u900f\u660e\u8f7d\u4f53\u6216\u5305\u88c5\u5668\u3002 \u53ea\u9700\u4f7f\u7528\u4e00\u884c\u4ee3\u7801\uff0c\u5c31\u53ef\u4ee5\u5b9a\u4e49\u4e00\u6761\u8bb0\u5f55\u53ca\u5176\u7ec4\u4ef6\u3002<\/p>\n<p>\u4f8b\u5982\uff0c\u4ee5\u4e0b\u5355\u884c\u4ee3\u7801\u4f1a\u521b\u5efa\u4e00\u6761\u65b0\u8bb0\u5f55 <code>Person<\/code>\uff0c\u540e\u8005\u53ef\u4ee5\u5b58\u50a8\u5176\u7ec4\u4ef6 <code>name<\/code> \u7684\u5b57\u7b26\u4e32\u503c\u548c <code>age<\/code> \u7684\u6574\u6570\u503c\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">record Person (String name, int age) { }<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u8bb0\u5f55\u8ba9\u60a8\u4e0d\u5fc5\u7f16\u5199\u6837\u677f\u4ee3\u7801\u3002 \u8bb0\u5f55\u4f1a\u9690\u5f0f\u751f\u6210\u5176\u6784\u9020\u51fd\u6570\u7684\u9ed8\u8ba4\u5b9e\u73b0\u3001\u5176\u7ec4\u4ef6\u7684\u8bbf\u95ee\u5668\u65b9\u6cd5\uff0c\u4ee5\u53ca <code>toString<\/code>\u3001<code>equals<\/code> \u548c <code>hashCode<\/code> \u7b49\u6548\u7528\u51fd\u6570\u65b9\u6cd5\u3002 \u4f7f\u7528\u8bb0\u5f55\u4f5c\u4e3a\u6570\u636e\u7684\u5305\u88c5\u5668\u65f6\uff0c\u60a8\u5f88\u53ef\u80fd\u9700\u8981\u5c06\u5176\u5c55\u5f00\u6765\u8bbf\u95ee\u5176\u7ec4\u4ef6\u3002 \u4f8b\u5982\uff0c\u5bf9\u4e8e\u8bb0\u5f55 <code>Person<\/code> \u7684\u5b9e\u4f8b\uff0c\u60a8\u53ef\u80fd\u60f3\u8981\u68c0\u67e5\u5176\u5e74\u9f84\u7ec4\u4ef6\u4ee5\u786e\u5b9a\u5b83\u6240\u4ee3\u8868\u7684\u4eba\u662f\u5426\u6709\u8d44\u683c\u6295\u7968\u3002 <code>isEligibleToVote<\/code> \u8fd9\u6837\u7684\u65b9\u6cd5\u53ef\u4ee5\u5b8c\u6210\u8fd9\u4e2a\u884c\u4e3a\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">boolean isEligibleToVote(Object obj) {\n   if (obj instanceof Person person) {\n       return person.age() &gt;= 18;\n   }\n   return false;\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u524d\u9762\u7684\u793a\u4f8b\u4f7f\u7528\u4e86 instanceof \u7684\u6a21\u5f0f\u5339\u914d\uff0c\u5b83\u58f0\u660e\u4e86\u4e00\u4e2a\u6a21\u5f0f\u53d8\u91cf <code>person<\/code>\uff0c\u56e0\u6b64\u60a8\u4e0d\u9700\u8981\u521b\u5efa\u5c40\u90e8\u53d8\u91cf\u6765\u5c06 <code>obj<\/code> \u8f6c\u6362\u4e3a <code>Person<\/code>\u3002<\/p>\n<p>\u8bb0\u5f55\u6a21\u5f0f\u66f4\u8fdb\u4e00\u6b65\u3002 \u5b83\u4e0d\u4ec5\u5c06\u5b9e\u4f8b\u4e0e\u8bb0\u5f55\u7c7b\u578b Person \u6bd4\u8f83\uff0c<i>\u8fd8<\/i>\u58f0\u660e\u4e86\u8bb0\u5f55\u7ec4\u4ef6\u7684\u53d8\u91cf\uff0c\u56e0\u6b64<i>\u60a8<\/i>\u65e0\u9700\u5b9a\u4e49\u5c40\u90e8\u53d8\u91cf\u6216\u4f7f\u7528\u6a21\u5f0f\u53d8\u91cf\u6765\u8bbf\u95ee\u8bb0\u5f55\u7684\u7ec4\u4ef6\u3002 \u8fd9\u90fd\u8981\u5f52\u529f\u4e8e\u7f16\u8bd1\u5668\u77e5\u9053\u8bb0\u5f55\u7ec4\u4ef6\u7684\u786e\u5207\u6570\u91cf\u548c\u7c7b\u578b\u3002<\/p>\n<p>\u4f7f\u7528\u8bb0\u5f55\u6a21\u5f0f\u91cd\u5199\u524d\u9762\u7684\u65b9\u6cd5\u3002 \u5c06\u8bb0\u5f55\u7c7b\u578b\u4e0e instanceof \u8fd0\u7b97\u7b26\u914d\u5408\u4f7f\u7528\u6216\u5728 switch case \u6807\u7b7e\u4e2d\u4f7f\u7528\u65f6\uff0cIntelliJ IDEA \u53ef\u4ee5\u68c0\u6d4b\u5230\u5b83\u5e76\u5efa\u8bae\u4f7f\u7528\u8bb0\u5f55\u6a21\u5f0f\uff1a<\/p>\n<p><!-- wp:image {\"className\":\"alignnone wp-image-16062\"} --><\/p>\n<figure class=\"wp-block-image alignnone wp-image-16062\"><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2022\/11\/eligibleToVote.gif\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><\/p>\n<p>\u8fd9\u662f\u4fee\u6539\u540e\u7684\u4ee3\u7801\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">boolean isEligibleToVote(Object obj) {\n   if (obj instanceof Person(String name, int age)) {\n       return age &gt;= 18;\n   }\n   return false;\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u5728\u524d\u9762\u7684\u4ee3\u7801\u4e2d\uff0c\u8bb0\u5f55\u6a21\u5f0f <code>Person(String name, int age)<\/code> \u4f3c\u4e4e\u5141\u8bb8\u4f7f\u7528\u53d8\u91cf <code>age<\/code> \u4ee3\u66ff <code>person.age()<\/code>\u3002 \u7136\u800c\uff0c\u7ee7\u7eed\u9605\u8bfb\uff0c\u60a8\u5c06\u4e86\u89e3\u8bb0\u5f55\u6a21\u5f0f\u80fd\u591f\u7b80\u5316\u4ee3\u7801\u7684\u610f\u56fe\uff0c\u8fd8\u6709\u52a9\u4e8e\u521b\u5efa\u7b80\u6d01\u7684\u6570\u636e\u5904\u7406\u4ee3\u7801\u3002<\/p>\n<p>\u5982\u679c\u60a8\u4e4b\u524d\u6ca1\u6709\u63a5\u89e6\u8fc7\u8bb0\u5f55\uff0c\u6216\u8005\u60f3\u66f4\u591a\u5730\u4e86\u89e3\u4ec0\u4e48\u662f\u8bb0\u5f55\uff0c\u6216\u8005 IntelliJ IDEA \u5982\u4f55\u63d0\u4f9b\u652f\u6301\uff0c\u8bf7\u53c2\u8003\u6211<a href=\"https:\/\/blog.jetbrains.com\/idea\/2021\/03\/java-16-and-intellij-idea\/#Why_use_records\">\u4e4b\u524d\u5173\u4e8e\u8bb0\u5f55\u7684\u535a\u5ba2<\/a>\u3002<\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"Named_Record_Pattern\" class=\"ez-toc-section\"><\/span><strong>\u547d\u540d\u8bb0\u5f55\u6a21\u5f0f<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>\u8bb0\u5f55\u6a21\u5f0f\u540e\u9762\u53ef\u4ee5\u8ddf\u968f\u4e00\u4e2a<i>\u8bb0\u5f55\u6a21\u5f0f\u53d8\u91cf<\/i>\u3002 \u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u8bb0\u5f55\u6a21\u5f0f\u88ab\u79f0\u4e3a<i>\u547d\u540d\u8bb0\u5f55\u6a21\u5f0f<\/i>\uff08\u867d\u7136\u6ca1\u6709\u5f97\u5230\u786e\u8ba4\uff0c\u4f46 <a href=\"https:\/\/openjdk.org\/jeps\/432\" target=\"_blank\" rel=\"noopener\">Java 20 \u7684\u8bb0\u5f55\u6a21\u5f0f\u7684\u7b2c\u4e8c\u7248\u9884\u89c8<\/a>\u53ef\u80fd\u4f1a\u653e\u5f03\u5bf9\u547d\u540d\u8bb0\u5f55\u6a21\u5f0f\u7684\u652f\u6301\uff09\u3002<\/p>\n<p>\u8bb0\u5f55\u6a21\u5f0f\u8fd8\u53ef\u4ee5\u4e3a\u5176\u7ec4\u4ef6\u5b9a\u4e49\u6a21\u5f0f\u53d8\u91cf\u3002 \u4f7f\u7528\u547d\u540d\u8bb0\u5f55\u6a21\u5f0f\u5e76\u5c1d\u8bd5\u4f7f\u7528\u8bb0\u5f55\u6a21\u5f0f\u53d8\u91cf\u8bbf\u95ee\u5176\u7ec4\u4ef6\u65f6\uff0cIntelliJ IDEA \u4f1a\u63d0\u793a\u60a8\u4e3a\u5176\u7ec4\u4ef6\u4f7f\u7528\u6a21\u5f0f\u53d8\u91cf\u3002 \u60a8\u5c06\u770b\u5230\u6b64\u7c7b\u4ee3\u7801\u4ee5\u9ec4\u8272\u80cc\u666f\u9ad8\u4eae\u663e\u793a\u3002 \u60a8\u53ef\u4ee5\u4f7f\u7528 Alt+Enter \u67e5\u770b\u5efa\u8bae\uff0c\u5e76\u63a5\u53d7\u4fee\u6539\u4ee3\u7801\u7684\u5efa\u8bae\uff1a<\/p>\n<p><!-- wp:image {\"className\":\"alignnone wp-image-16062\"} --><\/p>\n<figure class=\"wp-block-image alignnone wp-image-16062\"><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2022\/11\/named-record-pattern.gif\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"Record_Patterns_and_nulls\" class=\"ez-toc-section\"><\/span><strong>\u8bb0\u5f55\u6a21\u5f0f\u548c null<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>\u6211\u4eec\u56de\u987e\u4e00\u4e0b\u4e0a\u4e00\u90e8\u5206\u4e2d\u7684 <code>isEligibleToVote<\/code> \u65b9\u6cd5\u793a\u4f8b\u3002 \u5982\u679c\u5c06 <code>null<\/code> \u503c\u4f20\u9012\u7ed9\u4ee5\u4e0b\u65b9\u6cd5\u4f1a\u53d1\u751f\u4ec0\u4e48\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">boolean isEligibleToVote(Object obj) {\n   if (obj instanceof Person(String name, int age)) {\n       return age &gt;= 18;\n   }\n   return false;\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u7531\u4e8e null \u4e0d\u662f\u8bb0\u5f55\u6a21\u5f0f <code>Person(String name, int age)<\/code> \u7684\u5b9e\u4f8b\uff0c<code>instanceof<\/code> \u8fd0\u7b97\u7b26\u8fd4\u56de <code>false<\/code>\uff0c\u5e76\u4e14\u6a21\u5f0f\u53d8\u91cf <code>name<\/code> \u548c <code>age<\/code> \u672a\u521d\u59cb\u5316\u3002 \u8fd9\u5f88\u65b9\u4fbf\uff0c\u56e0\u4e3a\u8bb0\u5f55\u6a21\u5f0f\u4f1a\u5904\u7406 null\uff0c\u60a8\u4e0d\u9700\u8981\u5b9a\u4e49\u975e null \u68c0\u67e5\u3002<\/p>\n<p>\u4f46\u662f\uff0c\u5982\u679c\u7ec4\u4ef6 <code>name<\/code> \u7684\u503c\u4e3a null\uff0c\u5219\u6a21\u5f0f\u5c06\u88ab\u5339\u914d\u3002<\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"Nested_Record_Patterns_-_concise_code_and_clear_intent\" class=\"ez-toc-section\"><\/span><strong>\u5d4c\u5957\u8bb0\u5f55\u6a21\u5f0f \u2013 \u7b80\u6d01\u7684\u4ee3\u7801\u548c\u660e\u786e\u7684\u610f\u56fe<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>\u5c06\u53e6\u4e00\u6761\u8bb0\u5f55\u5b9a\u4e49\u4e3a\u5176\u7ec4\u4ef6\u7684\u8bb0\u5f55\u76f8\u5f53\u5e38\u89c1\u3002 \u4f8b\u5982\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">record Name       (String fName, String lName) { }\nrecord PhoneNumber(String areaCode, String number) { }\nrecord Country    (String countryCode, String countryName) { }\nrecord Passenger  (Name name, \n                   PhoneNumber phoneNumber, \n                   Country from, \n                   Country destination) { }<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u5982\u679c\u6ca1\u6709\u53ef\u4ee5\u68c0\u67e5 null \u7ec4\u4ef6\u503c\u7684\u8bb0\u5f55\u6a21\u5f0f\uff0c\u60a8\u5c06\u9700\u8981\u51e0\u4e2a null \u68c0\u67e5\u8fd0\u7b97\u6765\u5904\u7406\u8bb0\u5f55 <code>Passenger<\/code> \u7684 <code>fName<\/code> \u548c <code>countryCode<\/code> \u7684\u7ec4\u4ef6\u503c\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">boolean checkFirstNameAndCountryCode (Object obj) {\n   if (obj != null) {\n       if (obj instanceof Passenger passenger) {\n           Name name = null;\n           Country destination = null;\n \n           if (passenger.name() != null) {\n               name = passenger.name();\n \n               if (passenger.destination() != null) {\n                   destination = passenger.destination();\n \n                   String fName = name.fName();\n                   String countryCode = destination.countryCode();\n \n                   if (fName != null &amp;&amp; countryCode != null) {\n                       return fName.startsWith(\"Simo\") &amp;&amp;\n                              countryCode.equals(\"PRG\");\n                   }\n               }\n           }\n       }\n   }\n   return false;\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u540c\u6837\u7684\u884c\u4e3a\u53ef\u4ee5\u901a\u8fc7\u5d4c\u5957\u8bb0\u5f55\u6a21\u5f0f\u5b9e\u73b0\uff0c\u8fd9\u4e5f\u5c06\u4f7f\u4ee3\u7801\u7684\u610f\u56fe\u66f4\u52a0\u6e05\u6670\u3002 \u5982\u679c\u8bb0\u5f55\u7ec4\u4ef6 <code>name<\/code> \u548c <code>destination<\/code> \u4e3a null\uff0cinstanceof \u68c0\u67e5\u5c06\u5931\u8d25\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">boolean checkFirstNameAndCountryCodeAgain (Object obj) {\n   if (obj instanceof Passenger(Name (String fName, String lName),\n                                PhoneNumber phoneNumber,\n                                Country from,\n                                Country (String countryCode, String countryName) )) {\n \n       if (fName != null &amp;&amp; countryCode != null) {\n           return fName.startsWith(\"Simo\") &amp;&amp; countryCode.equals(\"PRG\");\n       }\n   }\n   return false;\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u5982\u524d\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u6240\u793a\uff0c\u60a8\u53ef\u4ee5\u6709\u9009\u62e9\u5730\u6dfb\u52a0\u4e3b\u8bb0\u5f55\u7ec4\u4ef6\u7684\u8bb0\u5f55\u6a21\u5f0f\u3002 \u4f8b\u5982\uff0c\u524d\u9762\u7684\u793a\u4f8b\u6ca1\u6709\u4e3a\u7ec4\u4ef6 <code>from<\/code> \u4f7f\u7528\u8bb0\u5f55\u6a21\u5f0f\u3002 \u4f46\u5b83\u4e3a\u4e3b\u8bb0\u5f55 <code>Passenger<\/code> \u7684\u8bb0\u5f55\u7ec4\u4ef6\u76ee\u6807\u4f7f\u7528\u8bb0\u5f55\u6a21\u5f0f\u3002 \u7b80\u800c\u8a00\u4e4b\uff0c\u5b9a\u4e49\u8bb0\u5f55\u6a21\u5f0f\u65f6\uff0c\u60a8\u53ef\u4ee5\u63a7\u5236\u8981\u63d0\u53d6\u5230\u6a21\u5f0f\u53d8\u91cf\u7684\u8be6\u7ec6\u4fe1\u606f\u3002 \u8fd9\u4e00\u529f\u80fd\u975e\u5e38\u9002\u5408\u6570\u636e\u5904\u7406\u5bc6\u96c6\u578b\u5e94\u7528\u7a0b\u5e8f\u3002<\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"Using_var_with_Record_patterns\" class=\"ez-toc-section\"><\/span><strong>\u5c06 var \u4e0e\u8bb0\u5f55\u6a21\u5f0f\u4e00\u8d77\u4f7f\u7528<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>\u6765\u56de\u987e\u4e00\u4e0b\u524d\u9762\u793a\u4f8b\u4e2d\u7684\u65b9\u6cd5 <code>checkFirstNameAndCountryCodeAgain<\/code>\uff0c\u5e76\u5c06\u4e00\u4e9b\u6a21\u5f0f\u53d8\u91cf\u7684\u7c7b\u578b\u5b9a\u4e49\u4e3a <code>var<\/code>\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">boolean checkFirstNameAndCountryCodeAgain (Object obj) {\n   if (obj instanceof Passenger(Name (String fName, var lName),\n                                var phoneNumber,\n                                Country from,\n                                Country (var countryCode, String countryName) )) {\n \n       if (fName != null &amp;&amp; countryCode != null) {\n           return fName.startsWith(\"Simo\") &amp;&amp; countryCode.equals(\"PRG\");\n       }\n   }\n   return false;\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u60a8\u53ef\u4ee5\u5c06\u90e8\u5206\u6216\u5168\u90e8\u6a21\u5f0f\u53d8\u91cf\u7684\u7c7b\u578b\u5b9a\u4e49\u4e3a var\u3002 \u5982\u679c\u60a8\u597d\u5947\u5b83\u4eec\u7684\u7c7b\u578b\uff0cIntelliJ IDEA \u53ef\u4ee5\u663e\u793a\uff1a<\/p>\n<p><!-- wp:image {\"className\":\"alignnone wp-image-16062\"} --><\/p>\n<figure class=\"wp-block-image alignnone wp-image-16062\"><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2022\/11\/using-var.gif\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"Record_patterns_and_generics\" class=\"ez-toc-section\"><\/span><strong>\u8bb0\u5f55\u6a21\u5f0f\u548c\u6cdb\u578b<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>\u5982\u679c\u8bb0\u5f55\u662f\u6cdb\u578b\uff0c\u5219\u5176\u8bb0\u5f55\u6a21\u5f0f\u5fc5\u987b\u4f7f\u7528\u6cdb\u578b\u7c7b\u578b\u3002 \u4f8b\u5982\uff0c\u5047\u8bbe\u7c7b <code>WristWatch<\/code> \u548c\u6cdb\u578b\u8bb0\u5f55 <code>Gift<\/code> \u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">class WristWatch {}\nrecord Gift&lt;T&gt;(T t) {}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u60a8\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u65b9\u6cd5<i>\u89e3\u5f00<\/i>\u8bb0\u5f55 <code>Gift<\/code> \u7684\u5b9e\u4f8b\u3002 \u60a8\u53ef\u4ee5\u4f7f\u7528 <code>var<\/code> \u6216 <code>WristWatch<\/code> \u4f5c\u4e3a\u6a21\u5f0f\u53d8\u91cf <code>watch<\/code> \u7684\u7c7b\u578b\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">void unwrap(Gift&lt;WristWatch&gt; obj) {\n   if (obj instanceof Gift&lt;WristWatch&gt; (var watch)) {\n       System.out.println(watch);\n   }\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u4f46\u662f\uff0c\u4ee5\u4e0b\u4ee3\u7801\u5c06\u4e0d\u8d77\u4f5c\u7528\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">static void cannotUnwap(Gift&lt;object&gt; obj) {\n   if (obj instanceof Gift(var s)) {   \/\/ won\u2019t compile              \n   \t\/\/..\n   }\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u4e0b\u4e00\u90e8\u5206\u4f7f\u7528\u8bb0\u5f55\u6a21\u5f0f\u548c switch \u8868\u8fbe\u5f0f\u521b\u5efa\u5f3a\u5927\u7684\u9012\u5f52\u65b9\u6cd5\u3002<\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"Record_patterns_switch_expressions_and_sealed_classes\" class=\"ez-toc-section\"><\/span><strong>\u8bb0\u5f55\u6a21\u5f0f\u3001switch \u8868\u8fbe\u5f0f\u548c\u5bc6\u5c01\u7c7b<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>\u7ed3\u5408\u8bb0\u5f55\u6a21\u5f0f\u3001switch \u8868\u8fbe\u5f0f\u548c\u5bc6\u5c01\u7c7b\uff0c\u60a8\u53ef\u4ee5\u521b\u5efa\u529f\u80fd\u5f3a\u5927\u3001\u7b80\u6d01\u4e14\u5bcc\u6709\u8868\u73b0\u529b\u7684\u4ee3\u7801\u6765\u5904\u7406\u6570\u636e\u3002 \u8fd9\u662f\u5bc6\u5c01\u63a5\u53e3 <code>TwoDimensional<\/code> \u7684\u793a\u4f8b\uff0c\u5b83\u7531\u8bb0\u5f55 <code>Point<\/code>\u3001<code>Line<\/code>\u3001<code>Triangle<\/code> \u548c <code>Square<\/code> \u5b9e\u73b0\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">sealed interface TwoDimensional {}\nrecord Point (int x, int y) implements TwoDimensional { }\nrecord Line    ( Point start, \n                 Point end) implements TwoDimensional { }\nrecord Triangle( Point pointA, \n                 Point pointB, \n                 Point PointC) implements TwoDimensional { }\nrecord Square  ( Point pointA, \n                 Point pointB, \n                 Point PointC, \n                 Point pointD) implements TwoDimensional { }<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u4e0b\u9762\u7684\u65b9\u6cd5\u5b9a\u4e49\u4e86\u4e00\u4e2a\u9012\u5f52\u65b9\u6cd5\u8fdb\u7a0b\uff0c\u5b83\u4f7f\u7528 switch \u6784\u9020\u8fd4\u56de\u4e8c\u7ef4\u56fe\u5f62\uff08\u5982 <code>Line<\/code>\u3001<code>Triangle<\/code> \u6216 <code>Square<\/code>\uff09\u4e2d\u6240\u6709\u70b9\u7684 <code>x<\/code> \u548c <code>y<\/code> \u5750\u6807\u4e4b\u548c\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">static int process(TwoDimensional twoDim) {\n   return switch (twoDim) {\n       case Point(int x, int y) -&gt; x + y;\n       case Line(Point a, Point b) -&gt; process(a) + process(b);\n       case Triangle(Point a, Point b, Point c) -&gt; \n                                 process(a) + process(b) + process(c);\n       case Square(Point a, Point b, Point c, Point d) -&gt; \n                                 process(a) + process(b) + process(c) + process(d);\n   };\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>IntelliJ IDEA \u8fd8\u4f1a\u5728\u6b64\u65b9\u6cd5\u7684\u95f4\u8ddd\u4e2d\u663e\u793a\u9012\u5f52\u8c03\u7528\u56fe\u6807\uff1a<\/p>\n<p><!-- wp:image --><\/p>\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2022\/11\/recursion.png\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"Record_patterns_in_Java_20\" class=\"ez-toc-section\"><\/span><strong>Java 20 \u4e2d\u7684\u8bb0\u5f55\u6a21\u5f0f<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>\u7531\u4e8e\u5f53\u524d\u72b6\u6001\u4e3a\u201cProposed to Target\u201d\uff0c\u9488\u5bf9 Java 20 \u7684<a href=\"https:\/\/openjdk.org\/jeps\/432\" target=\"_blank\" rel=\"noopener\">\u8bb0\u5f55\u6a21\u5f0f\u7684\u7b2c\u4e8c\u7248\u9884\u89c8<\/a>\u8ba1\u5212\u5bf9\u5176\u8fdb\u884c\u589e\u5f3a\u3002 \u9664\u4e86\u652f\u6301\u6cdb\u578b\u8bb0\u5f55\u6a21\u5f0f\u5b9e\u53c2\u7684\u7c7b\u578b\u63a8\u65ad\u5916\uff0c\u5b83\u8fd8\u63d0\u5230\u5728\u589e\u5f3a\u7684 <code>for<\/code> \u8bed\u53e5\u4e2d\u652f\u6301\u8bb0\u5f55\u6a21\u5f0f\u3002 \u6a21\u5f0f\u5339\u914d\u5fc5\u7136\u4f1a\u6539\u53d8\u60a8\u7684\u65e5\u5e38\u7f16\u7801\u3002<\/p>\n<p><!-- wp:heading {\"level\":1} --><\/p>\n<h1><strong>switch \u6a21\u5f0f\u5339\u914d \u2013 \u7b2c\u4e09\u7248\u9884\u89c8<\/strong><\/h1>\n<p><!-- \/wp:heading --><\/p>\n<p>\u5728 Java 17 \u4e2d\u4f5c\u4e3a\u9884\u89c8\u8bed\u8a00\u529f\u80fd\u5f15\u5165\u7684 switch \u6a21\u5f0f\u5339\u914d\u5728 Java 19 \u4e2d\u5904\u4e8e\u7b2c\u4e09\u7248\u9884\u89c8\u3002 \u5982\u679c\u60a8\u5bf9\u6b64\u4e3b\u9898\u8fd8\u4e0d\u719f\u6089\uff0c\u6216\u8005\u60f3\u8fdb\u4e00\u6b65\u4e86\u89e3\u5b83\u662f\u4ec0\u4e48\u6216 IntelliJ IDEA \u5982\u4f55\u652f\u6301\u5b83\uff0c\u8bf7\u53c2\u9605<a href=\"https:\/\/blog.jetbrains.com\/idea\/2021\/09\/java-17-and-intellij-idea\/#What_is_pattern_matching\">\u8fd9\u7bc7\u535a\u6587<\/a>\uff0c\u6211\u5728\u5176\u4e2d\u505a\u51fa\u4e86\u8be6\u7ec6\u4ecb\u7ecd \u2013 \u4ece\u4ec0\u4e48\u662f\u6a21\u5f0f\u5339\u914d\u5f00\u59cb\uff0c\u5230 instanceof \u7684\u6a21\u5f0f\u5339\u914d\uff0c\u7136\u540e\u662f switch \u7684\u6a21\u5f0f\u5339\u914d\u3002<\/p>\n<p>\u5728\u8fd9\u7bc7\u6587\u7ae0\u4e2d\uff0c\u6211\u5c06\u4ecb\u7ecd\u6a21\u5f0f\u5339\u914d\u4ece Java 18 \u4e2d\u7684\u7b2c\u4e8c\u7248\u9884\u89c8\u4ee5\u6765\u7684\u53d8\u5316\u3002 \u6211\u4eec\u4ece\u5728 switch \u5757\u4e2d\u4f7f\u7528 when \u5b50\u53e5\u7684\u7b2c\u4e00\u4e2a\u53d8\u5316\u5f00\u59cb\u3002<\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"Replacing_guarded_patterns_with_when_in_switch_blocks\" class=\"ez-toc-section\"><\/span><strong>\u5728 switch \u5757\u4e2d\u4f7f\u7528 when \u66ff\u6362\u53d7\u4fdd\u62a4\u7684\u6a21\u5f0f<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>\u60f3\u8c61\u4e00\u7ec4\u7c7b \u2013 Pollution\u3001AirPollution \u548c Deforestation\uff0c\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">class Pollution { }\nclass AirPollution extends Pollution {\n   public int getAQI() {\n       return 100;\n   }\n}\nclass Deforestation {\n   public int getTreeDamage() {\n       return 300;\n   }\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u5728\u4e4b\u524d\u7684 switch \u6a21\u5f0f\u5339\u914d\u9884\u89c8\u4e2d\uff0c\u60a8\u53ef\u4ee5\u4f7f\u7528\u53d7\u4fdd\u62a4\u7684\u6a21\u5f0f\u5411 case \u6807\u7b7e\u6dfb\u52a0\u6761\u4ef6\uff0c\u5373\u4f7f\u7528 &amp;&amp; \u5b9a\u4e49\u6761\u4ef6\u3002 \u4ee5\u4e0b\u4ee3\u7801\u4f7f\u7528 switch \u7684\u6a21\u5f0f\u5339\u914d\u548c\u53d7\u4fdd\u62a4\u7684\u6a21\u5f0f &amp;&amp; airPol.getAQI() &gt; 200\uff0c\u4ee5\u8fdb\u4e00\u6b65\u7ec6\u5316 <code>AirPollution<\/code> \u7684\u5b9e\u4f8b\uff0c\u6b64 switch \u5c06\u4e3a\u5176\u8fd4\u56de\u503c 500\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">public class MyEarth {\n   int getDamage(Object obj) {\n       return switch (obj) {\n           case AirPollution airPol &amp;&amp; airPol.getAQI() &gt; 200 -&gt; 500;\n           case Deforestation def -&gt; def.getTreeDamage();\n           case null, default -&gt; -1;\n       };\n   }\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u5728 switch \u6a21\u5f0f\u5339\u914d\u7684\u7b2c\u4e09\u7248\u9884\u89c8\u4e2d\uff0c\u53d7\u4fdd\u62a4\u7684\u6a21\u5f0f\u5df2\u88ab\u66ff\u6362\u4e3a when\uff08\u5982\u679c\u60a8\u4f7f\u7528\u8fc7 SQL \u67e5\u8be2\uff0c\u53ef\u4ee5\u5f88\u5bb9\u6613\u5730\u5c06\u5b83\u4eec\u8054\u7cfb\u8d77\u6765\uff09\u3002 \u6211\u4eec\u91cd\u5199\u524d\u9762\u7684\u793a\u4f8b\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">public class MyEarth {\n   int getDamage(Object obj) {\n       return switch (obj) {\n           case AirPollution airPol when airPol.getAQI() &gt; 200 -&gt; 500;\n           case Deforestation def -&gt; def.getTreeDamage();\n           case null, default -&gt; -1;\n       };\n   }\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u00a0<\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"New_inspections_-_Push_down_for_switch_expressions\" class=\"ez-toc-section\"><\/span><strong>\u65b0\u68c0\u67e5 \u2013 Push down for \u2018switch\u2019 expressions<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>IntelliJ IDEA \u6dfb\u52a0\u4e86\u4e00\u4e2a\u65b0\u68c0\u67e5 \u2013 Push down for \u2018switch\u2019 expressions\uff0c\u8fd9\u53ef\u4ee5\u8fdb\u4e00\u6b65\u5206\u79bb\u8ba1\u7b97\u53ca\u5176\u526f\u4f5c\u7528\uff0c\u5e2e\u52a9\u60a8\u4fee\u6539 switch \u8868\u8fbe\u5f0f\u3002 \u4f8b\u5982\uff0c\u8003\u8651\u4ee5\u4e0b\u4ee3\u7801\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">void printObject(Object obj) {\n   if (obj instanceof String s) {\n       System.out.println(\"String: \"\" + s + \"\"\");\n   } else if (obj instanceof Collection&lt;?&gt; c) {\n       System.out.println(\"Collection (size = \" + c.size() + \")\");\n   } else {\n       System.out.println(\"Other object: \" + obj);\n   }\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u7b2c\u4e00\u6b65\uff0c\u5e94\u7528 IntelliJ IDEA \u7684\u68c0\u67e5 Replace \u2018if\u2019 with \u2018switch\u2019\uff08\u5c06 \u2018if\u2019 \u66ff\u6362\u4e3a \u2018switch\u2019\uff09\uff0c\u5f97\u5230\u4ee5\u4e0b\u4ee3\u7801\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">void printObject(Object obj) {\n   switch (obj) {\n       case String s -&gt; System.out.println(\"String: \"\" + s + \"\"\");\n       case Collection&lt;?&gt; c -&gt; \n            System.out.println(\"Collection (size = \" + c.size() + \")\");\n       case null, default -&gt; System.out.println(\"Other object: \" + obj);\n   }\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u6ce8\u610f\uff0c\u6bcf\u4e2a switch \u6807\u7b7e\u90fd\u5305\u542b\u5bf9 System.out.println() \u7684\u8c03\u7528\u3002 \u73b0\u5728\uff0c\u60a8\u53ef\u4ee5\u5e94\u7528 IntelliJ IDEA \u7684\u68c0\u67e5\u201cPush down for \u2018switch\u2019 expression\u201d\uff0c\u5f97\u5230\u4ee5\u4e0b\u4ee3\u7801\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">void printObject(Object obj) {\n   System.out.println(switch (obj) {\n       case String s -&gt; \"String: \"\" + s + \"\"\";\n       case Collection&lt;?&gt; c -&gt; \"Collection (size = \" + c.size() + \")\";\n       case null, default -&gt; \"Other object: \" + obj;\n   });\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u6700\u540e\uff0c\u60a8\u53ef\u80fd\u60f3\u63d0\u53d6\u4e00\u4e2a\u53d8\u91cf\u6765\u5206\u79bb\u8ba1\u7b97\u548c\u526f\u4f5c\u7528\uff0c\u751f\u6210\u4ee5\u4e0b\u4ee3\u7801\uff1a<\/p>\n<p><!-- wp:code --><\/p>\n<pre class=\"EnlighterJSRAW\">void printObject(Object obj) {\n   final var representation = switch (obj) {\n       case String s -&gt; \"String: \"\" + s + \"\"\";\n       case Collection&lt;?&gt; c -&gt; \"Collection (size = \" + c.size() + \")\";\n       case null, default -&gt; \"Other object: \" + obj;\n   };\n   System.out.println(representation);\n}<\/pre>\n<p><!-- \/wp:code --><\/p>\n<p>\u4e0b\u9762\u7684 gif \u6db5\u76d6\u4ee5\u4e0a\u6240\u6709\u6b65\u9aa4\uff1a<\/p>\n<p><!-- wp:image {\"className\":\"alignnone wp-image-16062\"} --><\/p>\n<figure class=\"wp-block-image alignnone wp-image-16062\"><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2022\/11\/push-down-switch-2.gif\" alt=\"\" \/><\/figure>\n<p><!-- \/wp:image --><\/p>\n<p><!-- wp:heading {\"level\":2} --><\/p>\n<h2><span id=\"Pattern_Matching_for_switch_in_Java_20\" class=\"ez-toc-section\"><\/span><strong>Java 20 \u4e2d switch \u7684\u6a21\u5f0f\u5339\u914d<\/strong><\/h2>\n<p><!-- \/wp:heading --><\/p>\n<p>\u7531\u4e8e\u5f53\u524d\u72b6\u6001\u4e3a\u201cProposed to Target\u201d\uff0c\u9488\u5bf9 Java 20 \u7684<a href=\"https:\/\/openjdk.org\/jeps\/433\" target=\"_blank\" rel=\"noopener\">switch \u6a21\u5f0f\u5339\u914d\u7684\u7b2c\u56db\u7248\u9884\u89c8<\/a>\u8ba1\u5212\u6dfb\u52a0\u66f4\u591a\u66f4\u6539\u3002 \u9664\u4e86\u7b80\u5316 switch \u6807\u7b7e\u7684\u8bed\u6cd5\u5916\uff0c\u5b83\u8fd8\u5305\u62ec\u591a\u9879\u5176\u4ed6\u66f4\u6539\u3002<\/p>\n<p><!-- wp:heading {\"level\":1} --><\/p>\n<h1><strong>\u9884\u89c8\u529f\u80fd<\/strong><\/h1>\n<p><!-- \/wp:heading --><\/p>\n<p>Java \u7684\u65b0\u53d1\u5e03\u5468\u671f\u4e3a\u516d\u4e2a\u6708\uff0c\u65b0\u7684\u8bed\u8a00\u529f\u80fd\u4f5c\u4e3a\u9884\u89c8\u529f\u80fd\u53d1\u5e03\u3002 \u5b83\u4eec\u53ef\u80fd\u4f1a\u5728\u540e\u7eed Java \u7248\u672c\u7684\u7b2c\u4e8c\u7248\u6216\u7b2c\u4e09\u7248\u9884\u89c8\u4e2d\u91cd\u65b0\u5f15\u5165\uff0c\u53ef\u80fd\u6709\u4e5f\u53ef\u80fd\u6ca1\u6709\u66f4\u6539\u3002 \u8db3\u591f\u7a33\u5b9a\u540e\uff0c\u5b83\u4eec\u5c31\u4f1a\u4f5c\u4e3a\u6807\u51c6\u8bed\u8a00\u529f\u80fd\u6dfb\u52a0\u5230 Java \u4e2d\u3002<\/p>\n<p>\u9884\u89c8\u8bed\u8a00\u529f\u80fd\u662f\u5b8c\u6574\u7684\u4f46\u4e0d\u662f\u6c38\u4e45\u7684\uff0c\u8fd9\u5b9e\u9645\u4e0a\u610f\u5473\u7740\u529f\u80fd\u5df2\u7ecf\u51c6\u5907\u597d\u4f9b\u5f00\u53d1\u8005\u4f7f\u7528\uff0c\u53ea\u662f\u66f4\u7ec6\u81f4\u7684\u7ec6\u8282\u53ef\u80fd\u4f1a\u5728\u672a\u6765\u7684 Java \u7248\u672c\u4e2d\u6839\u636e\u5f00\u53d1\u8005\u53cd\u9988\u53d1\u751f\u53d8\u5316\u3002 \u4e0e API \u4e0d\u540c\uff0c\u8bed\u8a00\u529f\u80fd\u5728\u672a\u6765\u4e0d\u80fd\u88ab\u5f03\u7528\u3002 \u56e0\u6b64\uff0c\u5982\u679c\u60a8\u5bf9\u9884\u89c8\u8bed\u8a00\u529f\u80fd\u6709\u4efb\u4f55\u53cd\u9988\uff0c\u8bf7\u968f\u65f6\u5728 <a href=\"https:\/\/mail.openjdk.java.net\/mailman\/listinfo\/amber-dev\" target=\"_blank\" rel=\"noopener\">JDK \u90ae\u5bc4\u540d\u5355<\/a>\u4e2d\u5206\u4eab\uff08\u9700\u8981\u514d\u8d39\u6ce8\u518c\uff09\u3002<\/p>\n<p>\u7531\u4e8e\u8fd9\u4e9b\u529f\u80fd\u7684\u8fd0\u4f5c\u65b9\u5f0f\uff0cIntelliJ IDEA \u4ec5\u652f\u6301\u5f53\u524d JDK \u7684\u9884\u89c8\u529f\u80fd\u3002 \u9884\u89c8\u8bed\u8a00\u529f\u80fd\u53ef\u4ee5\u5728\u4e0d\u540c Java \u7248\u672c\u95f4\u53d8\u5316\uff0c\u76f4\u5230\u5176\u88ab\u79fb\u9664\u6216\u6dfb\u52a0\u4e3a\u6807\u51c6\u8bed\u8a00\u529f\u80fd\u3002 \u4f7f\u7528\u65e7\u7248\u672c Java SE Platform \u4e2d\u7684\u9884\u89c8\u8bed\u8a00\u529f\u80fd\u7684\u4ee3\u7801\u53ef\u80fd\u65e0\u6cd5\u5728\u65b0\u7248\u672c\u4e0a\u7f16\u8bd1\u6216\u8fd0\u884c\u3002 \u4f8b\u5982\uff0cJava 12 \u4e2d\u7684 switch \u8868\u8fbe\u5f0f\u53d1\u5e03\u65f6\u4f7f\u7528 break \u4ece\u5176\u5206\u652f\u8fd4\u56de\u4e00\u4e2a\u503c\uff0c\u540e\u6765\u6539\u4e3a yield\u3002 IntelliJ IDEA \u5df2\u7ecf\u4e0d\u518d\u652f\u6301\u4f7f\u7528 break \u4ece switch \u8868\u8fbe\u5f0f\u8fd4\u56de\u503c\u3002<\/p>\n<p><!-- wp:heading {\"level\":1} --><\/p>\n<h1><strong>\u603b\u7ed3<\/strong><\/h1>\n<p><!-- \/wp:heading --><\/p>\n<p>IntelliJ IDEA \u4e0d\u4ec5\u81f4\u529b\u4e8e\u652f\u6301\u65b0\u7684 Java \u529f\u80fd\uff0c\u8fd8\u5c06\u786e\u4fdd\u73b0\u6709\u610f\u56fe\u548c\u68c0\u67e5\u80fd\u591f\u4e0e\u5b83\u4eec\u4e00\u8d77\u5de5\u4f5c\u3002<\/p>\n<p>IntelliJ IDEA 2022.3 \u652f\u6301\u8bb0\u5f55\u6a21\u5f0f\u5e76\u589e\u5f3a\u4e86\u5bf9 switch \u7684\u6a21\u5f0f\u5339\u914d\u7684\u652f\u6301\u3002 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