{"id":203097,"date":"2025-05-22T09:08:02","date_gmt":"2025-05-22T01:08:02","guid":{"rendered":"https:\/\/server.hk\/cnblog\/203097\/"},"modified":"2025-05-22T09:08:02","modified_gmt":"2025-05-22T01:08:02","slug":"java%e5%87%bd%e6%95%b0%e5%bc%8f%e6%8e%a5%e5%8f%a3%e5%9c%a8%e6%95%b0%e6%8d%ae%e5%a4%84%e7%90%86%e4%b8%ad%e7%9a%84%e5%ba%94%e7%94%a8","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/203097\/","title":{"rendered":"Java\u51fd\u6570\u5f0f\u63a5\u53e3\u5728\u6570\u636e\u5904\u7406\u4e2d\u7684\u5e94\u7528"},"content":{"rendered":"<p><b><\/b>     <\/p>\n<h1>Java\u51fd\u6570\u5f0f\u63a5\u53e3\u5728\u6570\u636e\u5904\u7406\u4e2d\u7684\u5e94\u7528<\/h1>\n<p>\u4eca\u5929\u5c06\u7ed9\u5927\u5bb6\u5e26\u6765<span style=\"color: #FF6600;, Helvetica, Arial, sans-serif;font-size: 14px;background-color: #FFFFFF\">\u300aJava\u51fd\u6570\u5f0f\u63a5\u53e3\u5728\u6570\u636e\u5904\u7406\u4e2d\u7684\u5e94\u7528\u300b<\/span>\uff0c\u611f\u5174\u8da3\u7684\u670b\u53cb\u8bf7\u7ee7\u7eed\u770b\u4e0b\u53bb\u5427\uff01\u4ee5\u4e0b\u5185\u5bb9\u5c06\u4f1a\u6d89\u53ca\u5230<span style=\"color: #FF6600;, Helvetica, Arial, sans-serif;font-size: 14px;background-color: #FFFFFF\"><\/span>\u7b49\u7b49\u77e5\u8bc6\u70b9\uff0c\u5982\u679c\u4f60\u662f\u6b63\u5728\u5b66\u4e60<span style=\"color: #FF6600;, Helvetica, Arial, sans-serif;font-size: 14px;background-color: #FFFFFF\">\u6587\u7ae0<\/span>\u6216\u8005\u5df2\u7ecf\u662f\u5927\u4f6c\u7ea7\u522b\u4e86\uff0c\u90fd\u975e\u5e38\u6b22\u8fce\u4e5f\u5e0c\u671b\u5927\u5bb6\u90fd\u80fd\u7ed9\u6211\u5efa\u8bae\u8bc4\u8bba\u54c8~\u5e0c\u671b\u80fd\u5e2e\u52a9\u5230\u5927\u5bb6\uff01<\/p>\n<p>\u51fd\u6570\u5f0f\u63a5\u53e3\u5728\u6570\u636e\u5904\u7406\u4e2d\u7684\u5e94\u7528\u4ec0\u4e48\u662f\u51fd\u6570\u5f0f\u63a5\u53e3\uff1f\u51fd\u6570\u5f0f\u63a5\u53e3\u53ea\u5305\u542b\u4e00\u4e2a\u62bd\u8c61\u65b9\u6cd5\u7684\u63a5\u53e3\u3002\u6570\u636e\u5904\u7406\u4e2d\u7684\u5e94\u7528\uff1a\u6570\u636e\u8fc7\u6ee4\uff1a\u4f7f\u7528 filter() \u65b9\u6cd5\u4ec5\u4fdd\u7559\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7d20\u3002\u6570\u636e\u6620\u5c04\uff1a\u4f7f\u7528 map() \u65b9\u6cd5\u5c06\u6bcf\u4e2a\u5143\u7d20\u8f6c\u6362\u4e3a\u53e6\u4e00\u4e2a\u7c7b\u578b\u3002\u6570\u636e\u5206\u7ec4\uff1a\u4f7f\u7528 groupingBy() \u65b9\u6cd5\u6309\u952e\u5c06\u6570\u636e\u5206\u7ec4\u5230 Map \u4e2d\u3002\u6570\u636e\u805a\u5408\uff1a\u4f7f\u7528 reduce() \u65b9\u6cd5\u5c06\u6570\u636e\u7ec4\u5408\u6210\u4e00\u4e2a\u5355\u4e00\u503c\u3002\u5b9e\u6218\u6848\u4f8b\uff1a\u4f7f\u7528\u51fd\u6570\u5f0f\u63a5\u53e3\u8f7b\u677e\u89e3\u6790 JSON \u6570\u636e\u6587\u4ef6\u3002<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241028\/1730083711671efb7f946e5.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>Java \u51fd\u6570\u5f0f\u63a5\u53e3\u5728\u6570\u636e\u5904\u7406\u4e2d\u7684\u5e94\u7528<\/strong><\/p>\n<p><strong>\u4ec0\u4e48\u662f\u51fd\u6570\u5f0f\u63a5\u53e3\uff1f<\/strong><\/p>\n<p>\u51fd\u6570\u5f0f\u63a5\u53e3\u662f\u4e00\u4e2a\u63a5\u53e3\uff0c\u5176\u4e2d\u53ea\u5305\u542b\u4e00\u4e2a\u62bd\u8c61\u65b9\u6cd5\u3002\u5728 Java 8 \u4e2d\uff0c\u6b64\u7c7b\u63a5\u53e3\u4f7f\u7528 <code>@FunctionalInterface<\/code> \u6ce8\u89e3\u8fdb\u884c\u6807\u8bb0\u3002<\/p>\n<p><strong>lambda \u8868\u8fbe\u5f0f\u548c\u65b9\u6cd5\u5f15\u7528<\/strong><\/p>\n<p>lambda \u8868\u8fbe\u5f0f\u548c\u65b9\u6cd5\u5f15\u7528\u5141\u8bb8\u6211\u4eec\u521b\u5efa\u51fd\u6570\u5f0f\u63a5\u53e3\u7684\u5177\u4f53\u5b9e\u73b0\u65b9\u5f0f\u3002<\/p>\n<ul>\n<li><strong>lambda \u8868\u8fbe\u5f0f\uff1a<\/strong><code>\u53c2\u6570 -&gt; \u8868\u8fbe\u5f0f<\/code><\/li>\n<li><strong>\u65b9\u6cd5\u5f15\u7528\uff1a<\/strong><code>\u7c7b\u578b::\u65b9\u6cd5\u540d\u79f0<\/code><\/li>\n<\/ul>\n<p><strong>\u6570\u636e\u5904\u7406\u4e2d\u7684\u5e94\u7528<\/strong><\/p>\n<p>\u51fd\u6570\u5f0f\u63a5\u53e3\u5728\u6570\u636e\u5904\u7406\u4e2d\u6709\u4ee5\u4e0b\u5e94\u7528\uff1a<\/p>\n<p><strong>1. \u6570\u636e\u8fc7\u6ee4<\/strong><\/p>\n<p>\u4f7f\u7528 <code>filter()<\/code> \u65b9\u6cd5\uff0c\u6211\u4eec\u53ef\u4ee5\u8fc7\u6ee4\u6570\u636e\uff0c\u4ec5\u4fdd\u7559\u6ee1\u8db3\u7279\u5b9a\u6761\u4ef6\u7684\u5143\u7d20\u3002<\/p>\n<pre>List&lt;Integer&gt; numbers = List.of(1, 2, 3, 4, 5);\nList&lt;Integer&gt; evenNumbers = numbers.stream()\n        .filter(n -&gt; n % 2 == 0)\n        .toList();\nSystem.out.println(evenNumbers); \/\/ [2, 4]<\/pre>\n<p><strong>2. \u6570\u636e\u6620\u5c04<\/strong><\/p>\n<p>\u4f7f\u7528 <code>map()<\/code> \u65b9\u6cd5\uff0c\u6211\u4eec\u53ef\u4ee5\u5c06\u4e00\u4e2a\u96c6\u5408\u4e2d\u7684\u6bcf\u4e2a\u5143\u7d20\u8f6c\u6362\u4e3a\u53e6\u4e00\u4e2a\u7c7b\u578b\u3002<\/p>\n<pre>List&lt;String&gt; strings = List.of(\"1\", \"2\", \"3\");\nList&lt;Integer&gt; ints = strings.stream()\n        .map(Integer::parseInt)\n        .toList();\nSystem.out.println(ints); \/\/ [1, 2, 3]<\/pre>\n<p><strong>3. \u6570\u636e\u5206\u7ec4<\/strong><\/p>\n<p>\u4f7f\u7528 <code>groupingBy()<\/code> \u65b9\u6cd5\uff0c\u6211\u4eec\u53ef\u4ee5\u6309\u952e\u5c06\u6570\u636e\u5206\u7ec4\u5230 <code>Map<\/code> \u4e2d\u3002<\/p>\n<pre>List&lt;Person&gt; persons = List.of(\n        new Person(\"John\", 30),\n        new Person(\"Jane\", 25),\n        new Person(\"Michael\", 35)\n);\nMap&lt;Integer, List&lt;Person&gt;&gt; groupedByAge = persons.stream()\n        .collect(groupingBy(Person::getAge));\nSystem.out.println(groupedByAge); \/\/ {30=[John], 25=[Jane], 35=[Michael]}<\/pre>\n<p><strong>4. \u6570\u636e\u805a\u5408<\/strong><\/p>\n<p>\u4f7f\u7528 <code>reduce()<\/code> \u65b9\u6cd5\uff0c\u6211\u4eec\u53ef\u4ee5\u805a\u5408\u6570\u636e\uff0c\u5c06\u5b83\u4eec\u7ec4\u5408\u6210\u4e00\u4e2a\u5355\u4e00\u503c\u3002<\/p>\n<pre>Integer sumOfNumbers = numbers.stream()\n        .reduce((a, b) -&gt; a + b)\n        .orElse(0);\nSystem.out.println(sumOfNumbers); \/\/ 15<\/pre>\n<p><strong>\u5b9e\u6218\u6848\u4f8b\uff1a\u89e3\u6790 JSON \u6570\u636e<\/strong><\/p>\n<p>\u8003\u8651\u4e00\u4e2a\u5305\u542b JSON \u8868\u793a\u7684\u5458\u5de5\u6570\u636e\u7684\u6587\u672c\u6587\u4ef6\u3002\u6211\u4eec\u4f7f\u7528\u51fd\u6570\u5f0f\u63a5\u53e3\u53ef\u4ee5\u8f7b\u677e\u5730\u89e3\u6790\u6b64\u6570\u636e\uff1a<\/p>\n<pre>[\n  {\n    \"id\": 1,\n    \"name\": \"John\",\n    \"age\": 30\n  },\n  {\n    \"id\": 2,\n    \"name\": \"Jane\",\n    \"age\": 25\n  }\n]<\/pre>\n<pre>ObjectMapper mapper = new ObjectMapper();\nTypeReference&lt;List&lt;Employee&gt;&gt; typeReference = new TypeReference&lt;&gt;() {};\nList&lt;Employee&gt; employees = mapper.readValue(file, typeReference);\n\nList&lt;String&gt; employeeNames = employees.stream()\n        .map(Employee::getName)\n        .toList();\nSystem.out.println(employeeNames); \/\/ [John, Jane]<\/pre>\n<p>\u4ee5\u4e0a\u5c31\u662f\u672c\u6587\u7684\u5168\u90e8\u5185\u5bb9\u4e86\uff0c\u662f\u5426\u6709\u987a\u5229\u5e2e\u52a9\u4f60\u89e3\u51b3\u95ee\u9898\uff1f\u82e5\u662f\u80fd\u7ed9\u4f60\u5e26\u6765\u5b66\u4e60\u4e0a\u7684\u5e2e\u52a9\uff0c\u8bf7\u5927\u5bb6\u591a\u591a\u652f\u6301\uff01\u66f4\u591a\u5173\u4e8e\u6587\u7ae0\u7684\u76f8\u5173\u77e5\u8bc6\uff0c\u4e5f\u53ef\u5173\u6ce8\u516c\u4f17\u53f7\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Java\u51fd\u6570\u5f0f\u63a5\u53e3\u5728\u6570\u636e\u5904\u7406\u4e2d\u7684&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4925],"tags":[],"class_list":["post-203097","post","type-post","status-publish","format-standard","hentry","category-4925"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/203097","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=203097"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/203097\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=203097"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=203097"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=203097"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}