{"id":657571,"date":"2025-11-10T05:15:38","date_gmt":"2025-11-10T04:15:38","guid":{"rendered":"https:\/\/blog.jetbrains.com\/?post_type=kotlin&#038;p=657571"},"modified":"2025-11-10T05:15:42","modified_gmt":"2025-11-10T04:15:42","slug":"evaluating-kotlin-in-real-projects","status":"publish","type":"kotlin","link":"https:\/\/blog.jetbrains.com\/zh-hans\/kotlin\/2025\/11\/evaluating-kotlin-in-real-projects\/","title":{"rendered":"\u5728\u5b9e\u9645\u9879\u76ee\u4e2d\u8bc4\u4f30 Kotlin"},"content":{"rendered":"<p><em>\u5ba2\u5ea7\u6587\u7ae0\u4f5c\u8005\uff1a<a href=\"https:\/\/www.linkedin.com\/in\/urs-peter-70a2882\/\" target=\"_blank\" rel=\"noreferrer noopener\" data-type=\"link\" data-id=\"https:\/\/bit.ly\/urs-peter-linked-in\">Urs Peter<\/a>\uff0c\u9ad8\u7ea7\u8f6f\u4ef6\u5de5\u7a0b\u5e08\u517c JetBrains \u8ba4\u8bc1 Kotlin \u57f9\u8bad\u5e08\u3002 \u5bf9\u4e8e\u5e0c\u671b\u4ee5\u66f4\u7cfb\u7edf\u7684\u65b9\u5f0f\u63d0\u5347 Kotlin \u6280\u80fd\u7684\u8bfb\u8005\uff0cUrs \u8fd8\u5728 <\/em><em>Xebia Academy<\/em> \u4e3b\u529e\u4e86 <a href=\"https:\/\/academy.xebia.com\/upskilling\/kotlin-academy\/\" target=\"_blank\" rel=\"noreferrer noopener\"><em>Kotlin \u6280\u80fd\u63d0\u5347\u8ba1\u5212<\/em><\/a>\u3002<\/p>\n<p><em>\u672c\u6587\u4e3a<\/em><strong><em>\u5728\u4ee5 Java \u4e3a\u4e3b\u7684\u73af\u5883\u4e2d\u6210\u529f\u91c7\u7528 Kotlin \u7684\u7ec8\u6781\u6307\u5357<\/em><\/strong><em>\u7cfb\u5217\u7684\u7b2c\u4e8c\u7bc7\u6587\u7ae0\uff0c\u7cfb\u5217\u5c06\u4ece\u4e00\u4f4d\u5f00\u53d1\u8005\u4ea7\u751f\u597d\u5947\u5fc3\u5230\u516c\u53f8\u8303\u56f4\u8f6c\u578b\u8fd9\u4e00\u53d1\u5c55\u8fc7\u7a0b\uff0c\u9010\u6b65\u8bb2\u8ff0 Kotlin \u91c7\u7528\u5728\u5b9e\u9645\u56e2\u961f\u4e2d\u5982\u4f55\u589e\u957f\u3002<\/em><\/p>\n<p>\u9605\u8bfb\u7b2c\u4e00\u7bc7\uff1a<a href=\"https:\/\/blog.jetbrains.com\/kotlin\/2025\/10\/getting-started-with-kotlin-for-java-developers\/\" target=\"_blank\" rel=\"noreferrer noopener\">\u9762\u5411 Java \u5f00\u53d1\u8005\u7684 Kotlin \u4f7f\u7528\u5165\u95e8<\/a><\/p>\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/>\n<h2 class=\"wp-block-heading\"><strong>\u8bc4\u4f30\u9636\u6bb5\uff1a\u5728\u6f14\u7ec3\u573a\u5ef6\u7eed Kotlin \u91c7\u7528<\/strong><\/h2>\n<p>\u5728\u6d4b\u8bd5\u573a\u666f\u4e2d\u5bf9\u4f7f\u7528 Kotlin \u5f97\u5fc3\u5e94\u624b\u540e\uff0c\u4fbf\u53ef\u4ee5\u7740\u624b\u5f00\u5c55\u66f4\u6df1\u5165\u7684\u8bc4\u4f30\u3002 \u6709\u4e24\u79cd\u4e3b\u8981\u65b9\u5f0f\u4f9b\u60a8\u9009\u62e9\uff1a<\/p>\n<ol>\n<li><a href=\"#1.-build-a-new-microservice\/application-in-kotlin\" data-type=\"link\" data-id=\"https:\/\/blog.jetbrains.com\/#1.-build-a-new-microservice\/application-in-kotlin\">\u4f7f\u7528 Kotlin \u6784\u5efa\u65b0\u7684\u5fae\u670d\u52a1\/\u5e94\u7528\u7a0b\u5e8f<\/a><\/li>\n<li><a href=\"#2.-extend\/convert-an-existing-java-application\" data-type=\"link\" data-id=\"https:\/\/blog.jetbrains.com\/#2.-extend\/convert-an-existing-java-application\">\u6269\u5c55\/\u8f6c\u6362\u73b0\u6709\u7684 Java \u5e94\u7528\u7a0b\u5e8f<\/a><\/li>\n<\/ol>\n<h3 id=\"1.-build-a-new-microservice\/application-in-kotlin\" class=\"wp-block-heading\"><strong>1. \u4f7f\u7528 Kotlin \u6784\u5efa\u65b0\u7684\u5fae\u670d\u52a1\/\u5e94\u7528\u7a0b\u5e8f<\/strong><\/h3>\n<p>\u4ece\u5934\u5f00\u59cb\u5f00\u53d1\u65b0\u5e94\u7528\u7a0b\u5e8f\u6216\u5fae\u670d\u52a1\u80fd\u8ba9\u60a8\u4e0d\u53d7\u9057\u7559\u4ee3\u7801\u7684\u9650\u5236\uff0c\u5145\u5206\u4f53\u9a8c Kotlin \u7684\u5168\u90e8\u7279\u6027\u3002 \u8fd9\u79cd\u65b9\u5f0f\u5f80\u5f80\u80fd\u5e26\u6765\u6700\u4f73\u5b66\u4e60\u4f53\u9a8c\uff0c\u4e5f\u80fd\u6700\u6e05\u6670\u5730\u5c55\u73b0 Kotlin \u7684\u4f18\u52bf\u3002<\/p>\n<div class=\"wp-block-columns is-layout-flex wp-container-3 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis: 66.66%;\">\n<p><strong>\u4e13\u5bb6\u63d0\u793a<\/strong>\uff1a\u6b64\u9636\u6bb5\u53ef\u4ee5\u5bfb\u6c42\u4e13\u5bb6\u652f\u6301\u3002 \u5f00\u53d1\u8005\u56fa\u7136\u5bf9\u81ea\u8eab\u80fd\u529b\u5145\u6ee1\u4fe1\u5fc3\uff0c\u4f46\u907f\u514d\u65e9\u671f\u9519\u8bef\uff08\u4f8b\u5982\u7f16\u5199 Java \u98ce\u683c\u7684 Kotlin \u4ee3\u7801\u3001\u4e0d\u4f7f\u7528 Kotlin \u539f\u751f\u5e93\uff09\uff0c\u53ef\u4ee5\u51cf\u5c11\u6570\u6708\u7684\u6280\u672f\u503a\u52a1\u3002<\/p>\n<\/div>\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis: 33.33%;\">\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" loading=\"lazy\" class=\"wp-image-646384\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2025\/10\/unnamed-5.png\" alt=\"\" width=\"600\" height=\"400\" \/><\/figure>\n<\/div>\n<\/div>\n<p>\u5bf9\u4e8e\u6709 Java \u80cc\u666f\u7684\u5f00\u53d1\u8005\uff0c\u4ee5\u4e0b\u662f\u4f7f\u7528 Kotlin \u65f6\u53ef\u4ee5\u89c4\u907f\u7684\u5e38\u89c1\u9677\u9631\uff1a<\/p>\n<p><em>\u9677\u9631\uff1a\u9009\u62e9\u4e0e Java \u9879\u76ee\u4e2d\u4e0d\u540c\u7684\u6846\u67b6\u3002<\/em><\/p>\n<p>\u5efa\u8bae\uff1a<strong>\u575a\u6301\u4f7f\u7528\u73b0\u6709\u7684\u6846\u67b6<\/strong>\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5728 Java \u9879\u76ee\u4e2d\u4f7f\u7528\u7684\u662f Spring Boot\uff0c\u90a3\u4e48\u5728 Kotlin \u4e2d\u7ee7\u7eed\u4f7f\u7528\u5373\u53ef\u3002 Spring Boot \u5bf9 Kotlin \u7684\u652f\u6301\u582a\u79f0\u4e00\u6d41\uff0c\u56e0\u6b64\u6362\u7528\u5176\u4ed6\u6846\u67b6\u5e76\u65e0\u989d\u5916\u76ca\u5904\u3002 \u6b64\u5916\uff0c\u60a8\u4e0d\u4ec5\u8981\u5b66\u4e60\u65b0\u8bed\u8a00\uff0c\u8fd8\u8981\u989d\u5916\u5b66\u4e60\u65b0\u6846\u67b6\uff0c\u8fd9\u53ea\u4f1a\u5f92\u589e\u590d\u6742\u6027\uff0c\u5e76\u65e0\u4efb\u4f55\u4f18\u52bf\u3002<\/p>\n<p><strong>\u91cd\u8981\u63d0\u793a<\/strong>\uff1aSpring \u4f1a\u4e0e Kotlin \u7684\u201c\u8bbe\u8ba1\u4e2d\u7ee7\u627f\u201d\u539f\u5219\u4ea7\u751f\u51b2\u7a81\uff0c\u8be5\u539f\u5219\u8981\u6c42\u7c7b\u5fc5\u987b\u88ab\u663e\u5f0f\u6807\u8bb0\u4e3a open \u624d\u80fd\u8fdb\u884c\u6269\u5c55\u3002<\/p>\n<p>\u4e3a\u907f\u514d\u7ed9\u6240\u6709\u4e0e Spring \u76f8\u5173\u7684\u7c7b\uff08\u5982 <code>@Configuration<\/code> \u7b49\uff09\u90fd\u6dfb\u52a0 open \u5173\u952e\u5b57\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u6784\u5efa\u63d2\u4ef6\uff1a<a href=\"https:\/\/kotlinlang.org\/docs\/all-open-plugin.html#spring-support\" target=\"_blank\" rel=\"noreferrer noopener\">https:\/\/kotlinlang.org\/docs\/all-open-plugin.html#spring-support<\/a>\u3002 \u5982\u679c\u60a8\u4f7f\u7528\u77e5\u540d\u7684\u5728\u7ebf\u5de5\u5177 <a href=\"https:\/\/start.spring.io\/\" target=\"_blank\" rel=\"noreferrer noopener\">Spring Initializr<\/a> \u521b\u5efa Spring \u9879\u76ee\uff0c\u6b64\u6784\u5efa\u63d2\u4ef6\u5df2\u4e3a\u60a8\u9884\u5148\u914d\u7f6e\u3002<\/p>\n<p><em>\u9677\u9631\uff1a\u4ee5 Java \u98ce\u683c\u7f16\u5199 Kotlin \u4ee3\u7801\uff0c\u4f9d\u8d56\u5e38\u89c1\u7684 Java API \u800c\u975e Kotlin \u6807\u51c6\u5e93\uff1a<\/em><\/p>\n<p>\u8fd9\u79cd\u9677\u9631\u4e0d\u80dc\u679a\u4e3e\uff0c\u4e0b\u9762\u6211\u4eec\u6765\u91cd\u70b9\u8bf4\u8bf4\u6700\u5e38\u89c1\u7684\u51e0\u79cd\uff1a<\/p>\n<h4 class=\"wp-block-heading\"><em>\u9677\u9631 1\uff1a\u4f7f\u7528 Java \u6d41\u800c\u975e Kotlin \u96c6\u5408<\/em><\/h4>\n<p>\u5efa\u8bae\uff1a<strong>\u59cb\u7ec8\u4f7f\u7528 Kotlin \u96c6\u5408<\/strong>\u3002<\/p>\n<p>Kotlin \u96c6\u5408\u4e0e Java \u96c6\u5408\u53ef\u4ee5\u5b8c\u5168\u4e92\u64cd\u4f5c\uff0c\u540c\u65f6\u914d\u5907\u4e86\u7b80\u6d01\u4e14\u529f\u80fd\u4e30\u5bcc\u7684\u9ad8\u9636\u51fd\u6570\uff0c\u8fd9\u6837\u4e00\u6765\uff0c\u5c31\u6ca1\u6709\u5fc5\u8981\u4f7f\u7528 Java \u6d41\u4e86\u3002<\/p>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u793a\u4f8b\uff0c\u65e8\u5728\u6309\u4ea7\u54c1\u7c7b\u522b\u5206\u7ec4\uff0c\u9009\u51fa\u8425\u6536\uff08\u4ef7\u683c * \u9500\u91cf\uff09\u6700\u9ad8\u7684\u524d 3 \u6b3e\u4ea7\u54c1\uff1a<\/p>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">record Product(String name, String category, double price, int sold){}\n\nList products = List.of(\n           new Product(\"Lollipop\", \"sweets\", 1.2, 321),\n           new Product(\"Broccoli\", \"vegetable\", 1.8, 5);\n\nMap&lt;String, List&gt; top3RevenueByCategory =\n       products.stream()\n          .collect(Collectors.groupingBy(\n                Product::category,\n                Collectors.collectingAndThen(\n                    Collectors.toList(),\n                    list -&gt; list.stream()\n                              .sorted(Comparator.comparingDouble(\n                                  (Product p) -&gt; p.price() * p.sold())\n                                   .reversed())\n                                   .limit(3)\n                                   .toList()\n                       \t\t)\n          )\n);<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">val top3RevenueByCategory: Map&lt;String, List&gt; =\n   products.groupBy { it.category }\n       .mapValues { (_, list) -&gt;\n           list.sortedByDescending { it.price * it.sold }.take(3)\n       }<\/pre>\n<p>Kotlin \u4e0e Java \u7684\u4e92\u64cd\u4f5c\u6027\u8ba9\u60a8\u53ef\u4ee5\u50cf\u4f7f\u7528\u539f\u751f Kotlin \u7c7b\u4e00\u6837\u5904\u7406 Java \u7c7b\u548c\u8bb0\u5f55\uff0c\u4e0d\u8fc7\u60a8\u4e5f\u53ef\u4ee5\u6539\u7528 Kotlin (data) \u7c7b\u3002<\/p>\n<h4 class=\"wp-block-heading\"><em>\u9677\u9631 2\uff1a\u6301\u7eed\u4f7f\u7528 Java \u7684 Optional\u3002<\/em><\/h4>\n<p>\u5efa\u8bae\uff1a<strong>\u5584\u7528\u53ef\u4e3a null \u7684\u7c7b\u578b<\/strong>\u3002<\/p>\n<p>Java \u5f00\u53d1\u8005\u8f6c\u5411 Kotlin \u7684\u6838\u5fc3\u539f\u56e0\u4e4b\u4e00\u5c31\u662f Kotlin \u5185\u7f6e\u7684\u4e3a null \u6027\u652f\u6301\uff0c\u8fd9\u80fd\u5f7b\u5e95\u907f\u514d NullPointerExceptions\u3002 \u56e0\u6b64\uff0c\u5c3d\u91cf\u53ea\u4f7f\u7528\u53ef\u4e3a null \u7684\u7c7b\u578b\uff0c\u4e0d\u8981\u518d\u7528 Optional\u3002 \u5982\u679c\u60a8\u7684\u63a5\u53e3\u4e2d\u8fd8\u5b58\u5728 Optional\uff0c \u53ea\u9700\u5c06\u5176\u8f6c\u6362\u4e3a\u53ef\u4e3a null \u7684\u7c7b\u578b\u5373\u53ef\u8f7b\u677e\u79fb\u9664\uff0c\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/Let\u2019s assume this repository is hard to change, because it\u2019s a library you depend on\nclass OrderRepository {\n      \/\/it returns Optional, but we want nullable types\n      fun getOrderBy(id: Long): Optional = \u2026\n}\n\n\/\/Simply add an extension method and apply the orElse(null) trick\nfun OrderRepository.getOrderByOrNull(id: Long): Order? = \n                                    getOrderBy(id).orElse(null)\n\n\/\/Now enjoy the safety and ease of use of nullable types:\n\n\/\/Past:\n val g = repository.getOrderBy(12).flatMap { product -&gt;\n     product.goody.map { it.name }\n}.orElse(\"No goody found\")\n\n\/\/Future:\n val g = repository.getOrderByOrNull(12)?.goody?.name ?: \"No goody found\"<\/pre>\n<h4 class=\"wp-block-heading\"><em>\u9677\u9631 3\uff1a\u7ee7\u7eed\u4f7f\u7528\u9759\u6001\u5305\u88c5\u5668\u3002<\/em><\/h4>\n<p>\u5efa\u8bae\uff1a<strong>\u5584\u7528\u6269\u5c55\u65b9\u6cd5<\/strong>\u3002<\/p>\n<p>\u6269\u5c55\u65b9\u6cd5\u80fd\u5e26\u6765\u8bf8\u591a\u597d\u5904\uff1a<\/p>\n<ul>\n<li>\u76f8\u6bd4\u5305\u88c5\u5668\uff0c\u6269\u5c55\u65b9\u6cd5\u80fd\u8ba9\u4ee3\u7801\u66f4\u6d41\u7545\u3001\u53ef\u8bfb\u6027\u66f4\u5f3a\u3002<\/li>\n<li>\u6269\u5c55\u65b9\u6cd5\u53ef\u4ee5\u901a\u8fc7\u4ee3\u7801\u8865\u5168\u529f\u80fd\u627e\u5230\uff0c\u800c\u5305\u88c5\u5668\u5219\u4e0d\u80fd\u3002<\/li>\n<li>\u7531\u4e8e\u6269\u5c55\u65b9\u6cd5\u9700\u8981\u5bfc\u5165\uff0c\u60a8\u53ef\u4ee5\u5728\u5e94\u7528\u7a0b\u5e8f\u7684\u7279\u5b9a\u90e8\u5206\u6709\u9009\u62e9\u5730\u4f7f\u7528\u6269\u5c55\u529f\u80fd\u3002<\/li>\n<\/ul>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/Very common approach in Java to add additional helper methods\npublic class DateUtils {\n      public static final DateTimeFormatter DEFAULT_DATE_TIME_FORMATTER = \n           DateTimeFormatter.ofPattern(\"yyyy-MM-dd HH:mm:ss\");\n\n      public String formatted(LocalDateTime dateTime, \n\t\t              DateTimeFormatter formatter) {\n         return dateTime.format(formatter);\n      }\n\n      public String formatted(LocalDateTime dateTime) {\n         return formatted(dateTime, DEFAULT_DATE_TIME_FORMATTER);\n      }\n}\n\n\/\/Usage\n formatted(LocalDateTime.now());\n<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">val DEFAULT_DATE_TIME_FORMATTER: DateTimeFormatter = \nDateTimeFormatter.ofPattern(\"yyyy-MM-dd HH:mm:ss\")\n\n\/\/Use an extension method, including a default argument, which omits the need for an overloaded method.\u00a0\nfun LocalDateTime.asString(\n\u00a0\u00a0\u00a0formatter: DateTimeFormatter = DEFAULT_DATE_TIME_FORMATTER): String =\u00a0\n      this.format(formatter)\n\n\/\/Usage\nLocalDateTime.now().formatted()<\/pre>\n<p>\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0cKotlin \u63d0\u4f9b\u4e86\u9876\u5c42\u65b9\u6cd5\u548c\u53d8\u91cf\u3002 \u8fd9\u610f\u5473\u7740\u6211\u4eec\u53ef\u4ee5\u76f4\u63a5\u5c06 <em><code>DEFAULT_DATE_TIME_FORMATTER<\/code><\/em> \u4e4b\u7c7b\u7684\u5143\u7d20\u58f0\u660e\u4e3a\u9876\u5c42\uff0c\u800c\u65e0\u9700\u50cf Java \u90a3\u6837\u5fc5\u987b\u7ed1\u5b9a\u5230\u67d0\u4e2a\u5bf9\u8c61\u3002<\/p>\n<h4 class=\"wp-block-heading\"><em>\u9677\u9631 4\uff1a\u4f9d\u8d56\uff08\u8e69\u811a\u7684\uff09Java API<\/em><\/h4>\n<p>\u5efa\u8bae\uff1a<strong>\u4f7f\u7528 Kotlin \u66f4\u7b80\u6d01\u6d41\u7545\u7684\u66ff\u4ee3\u65b9\u6848\u3002\u00a0<\/strong><\/p>\n<p>Kotlin \u6807\u51c6\u5e93\u901a\u8fc7\u6269\u5c55\u65b9\u6cd5\u8ba9 Java \u5e93\u7684\u4f7f\u7528\u4f53\u9a8c\u53d8\u5f97\u66f4\u53cb\u597d\uff0c\u5c3d\u7ba1\u5176\u5e95\u5c42\u5b9e\u73b0\u4f9d\u7136\u662f Java\u3002 \u51e0\u4e4e\u6240\u6709\u4e3b\u6d41\u7684\u7b2c\u4e09\u65b9\u5e93\u548c\u6846\u67b6\uff08\u5982 Spring\uff09\u90fd\u91c7\u53d6\u4e86\u540c\u6837\u7684\u505a\u6cd5\u3002<\/p>\n<p><strong>\u6807\u51c6\u5e93\u793a\u4f8b\uff1a<\/strong><\/p>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">String text;\ntry (\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0var reader = new BufferedReader(\n                  new InputStreamReader(new FileInputStream(\"out.txt\"), \n            StandardCharsets.UTF_8))) {\n\u00a0\u00a0\u00a0text = reader\n            .lines()\n            .collect(Collectors.joining(System.lineSeparator()));\n}\nSystem.out.println(\"Downloaded text: \" +\u00a0 text + \"n\");<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/Kotlin has enhanced the Java standard library with many powerful extension methods, like on java.io.*, which makes input stream processing a snap due to its fluent nature, fully supported by code completion\n\nval text = FileInputStream(\"path\").use {\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0     it.bufferedReader().readText()\n           }\nprintln(\"Downloaded text: $textn\");<\/pre>\n<p><strong>Spring \u793a\u4f8b<\/strong>\uff1a<br \/>\n<strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">final var books =\u00a0 RestClient.create()\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0.get()\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0.uri(\"http:\/\/...\/api\/books\")\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0.retrieve()\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0.body( new ParameterizedTypeReference&lt;List&gt;(){}); \/\/ \u21e6 inconvenient ParameterizedTypeReference<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">import org.springframework.web.client.body\nval books = RestClient.create()\n\u00a0\u00a0\u00a0.get()\n\u00a0\u00a0\u00a0.uri(\"http:\/\/...\/api\/books\")\n\u00a0\u00a0\u00a0.retrieve()\n\u00a0\u00a0\u00a0.body&lt;List&gt;() \/\/\u21e6 Kotlin offers an extension that only requires the type without the need for a ParameterizedTypeReference<\/pre>\n<h4 class=\"wp-block-heading\"><em>\u9677\u9631 5\uff1a\u4e3a\u6bcf\u4e2a public \u7c7b\u5206\u522b\u521b\u5efa\u4e00\u4e2a\u6587\u4ef6<\/em><\/h4>\n<p>\u5efa\u8bae\uff1a<strong>\u5c06\u76f8\u5173\u7684 public \u7c7b\u5408\u5e76\u5230\u4e00\u4e2a\u6587\u4ef6\u4e2d\u3002\u00a0<\/strong><\/p>\n<p>\u8fd9\u6837\u4e00\u6765\uff0c\u65e0\u9700\u6d4f\u89c8\u6570\u5341\u4e2a\u6587\u4ef6\uff0c\u5373\u53ef\u6e05\u6670\u4e86\u89e3\u67d0\u4e2a\uff08\u5b50\uff09\u9886\u57df\u7684\u7ed3\u6784\u3002<\/p>\n<p><strong>Java<\/strong><\/p>\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" loading=\"lazy\" class=\"wp-image-647331\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2025\/10\/unnamed-15.png\" alt=\"\" width=\"1114\" height=\"934\" \/><\/figure>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/For domain classes consider data classes - see why below\ndata class User(val email: String,\n            \/\/Use nullable types for safety and expressiveness\n\u00a0 \u00a0        val avatarUrl: URL? = null,\u00a0\n           var isEmailVerified: Boolean)\n\ndata class Account(val user:User,\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0val address: Address,\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0val mfaEnabled:Boolean,\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0val createdAt: Instant)\n\ndata class Address(val street: String,\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0val city: String,\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 val postalCode: String)<\/pre>\n<h4 class=\"wp-block-heading\"><em>\u9677\u9631 6\uff1a\u4f9d\u8d56\u53ef\u53d8\u7f16\u7a0b\u8303\u5f0f<\/em><\/h4>\n<p>\u5efa\u8bae\uff1a<strong>\u4e3b\u52a8\u91c7\u7528\u4e0d\u53ef\u53d8\u6027 \u2013 \u8fd9\u662f Kotlin \u7684\u9ed8\u8ba4\u539f\u5219<\/strong><\/p>\n<p>\u8bb8\u591a\u7f16\u7a0b\u8bed\u8a00\uff08\u5305\u62ec Java\uff09\u7684\u8d8b\u52bf\u5df2\u5341\u5206\u660e\u663e\uff1a\u4e0d\u53ef\u53d8\u6027\u6b63\u9010\u6e10\u53d6\u4ee3\u53ef\u53d8\u6027\u3002<\/p>\n<p>\u539f\u56e0\u5f88\u7b80\u5355\uff1a\u4e0d\u53ef\u53d8\u6027\u53ef\u4ee5\u907f\u514d\u610f\u5916\u7684\u526f\u4f5c\u7528\uff0c\u8ba9\u4ee3\u7801\u66f4\u5b89\u5168\u3001\u66f4\u53ef\u9884\u6d4b\uff0c\u4e5f\u66f4\u6613\u4e8e\u7406\u89e3\u3002 \u5b83\u8fd8\u80fd\u7b80\u5316\u5e76\u53d1\uff0c\u56e0\u4e3a\u4e0d\u53ef\u53d8\u6570\u636e\u53ef\u4ee5\u5728\u591a\u4e2a\u7ebf\u7a0b\u95f4\u81ea\u7531\u5171\u4eab\uff0c\u4e14\u4e0d\u5b58\u5728\u7ade\u4e89\u6761\u4ef6\u7684\u98ce\u9669\u3002<\/p>\n<p>\u6b63\u56e0\u4e3a\u5982\u6b64\uff0c\u5927\u591a\u6570\u73b0\u4ee3\u8bed\u8a00\uff08\u5305\u62ec Kotlin \u5728\u5185\uff09\u8981\u4e48\u9ed8\u8ba4\u5f3a\u8c03\u4e0d\u53ef\u53d8\u6027\uff0c\u8981\u4e48\u5927\u529b\u5021\u5bfc\u4e0d\u53ef\u53d8\u6027\u3002 \u5728 Kotlin \u4e2d\uff0c\u4e0d\u53ef\u53d8\u6027\u662f\u9ed8\u8ba4\u9009\u62e9\uff0c\u4e0d\u8fc7\u5728\u786e\u5b9e\u9700\u8981\u65f6\uff0c\u4ecd\u7136\u53ef\u4ee5\u9009\u62e9\u53ef\u53d8\u6027\u3002<\/p>\n<p>\u4ee5\u4e0b\u662f\u5173\u4e8e Kotlin <strong>\u4e0d\u53ef\u53d8\u6027\u5229\u5668<\/strong>\u7684\u5feb\u901f\u6307\u5357\uff1a<\/p>\n<p>1. \u4f18\u5148\u4f7f\u7528 <code>val<\/code> \u800c\u975e <code>var<\/code><\/p>\n<p>\u4f18\u5148\u9009\u62e9 <code>val<\/code> \u800c\u975e <code>var<\/code>\u3002 \u5982\u679c\u60a8\u4f7f\u7528\u4e86\u672c\u53ef\u66ff\u6362\u4e3a <code>val<\/code> \u7684 <code>var<\/code>\uff0cIntelliJ IDEA \u4f1a\u901a\u77e5\u60a8\u3002<\/p>\n<p>2. \u4f7f\u7528\uff08\u4e0d\u53ef\u53d8\u7684\uff09data \u7c7b\u4e0e <code>copy(...)<\/code><\/p>\n<p>\u5bf9\u4e8e\u9886\u57df\u76f8\u5173\u7684\u7c7b\uff0c\u8bf7\u4f7f\u7528 <code>data<\/code> \u7c7b\u4e0e <code>val<\/code>\u3002 Kotlin <code>data<\/code> \u7c7b\u5e38\u88ab\u62ff\u6765\u4e0e Java <code>records<\/code> \u4f5c\u6bd4\u8f83\u3002 \u5c3d\u7ba1\u4e8c\u8005\u5b58\u5728\u4e00\u5b9a\u91cd\u53e0\uff0c\u4f46 <code>data<\/code> \u7c7b\u63d0\u4f9b\u4e86\u4e00\u4e2a\u6740\u624b\u950f\u7ea7\u7279\u6027 <code>copy(...)<\/code>\u3002\u7f3a\u5c11\u8fd9\u4e00\u65b9\u6cd5\u4f1a\u5bfc\u81f4 <code>records<\/code> \u7684\u8f6c\u6362\u64cd\u4f5c\uff08\u8fd9\u5728\u4e1a\u52a1\u903b\u8f91\u4e2d\u7ecf\u5e38\u9700\u8981\uff09\u53d8\u5f97\u5341\u5206\u7e41\u7410\uff1a<\/p>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/only immutable state\npublic record Person(String name, int age) {\n\u00a0\u00a0\u00a0\/\/Lack of default parameters requires overloaded constructor\n\u00a0\u00a0\u00a0public Person(String name) {\u00a0\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0this(name, 0);\n\u00a0\u00a0\u00a0}\n\u00a0\u00a0\u00a0\/\/+ due to lack of String interpolation\n\u00a0 public String sayHi() {\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return \"Hello, my name is \" + name + \" and I am \" + age + \" years old.\";\n\u00a0\u00a0\u00a0}\n}\n\n\/\/Usage\nfinal var jack = new Person(\"Jack\", 42);\njack: Person[name=Jack, age=5]\n\n\/\/The issue is here: transforming a record requires manually copying the identical state to the new instance \u2639\ufe0f\nfinal var fred = new Person(\"Fred\", jack.name);<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/also supports mutable state (var)\ndata class Person(val name: String,\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0val age: Int = 0) {\n\u00a0 \/\/string interpolation\n\u00a0 fun sayHi() = \"Hi, my name is $name and I am $age years old.\"\n}\nval jack = Person(\"Jack\", 42)\njack: Person(name=Jack, age=42)\n\n\/\/Kotlin offers the copy method, which, due to the \u2018named argument\u2019 feature, allows you to only adjust the state you want to change \ud83d\ude03\nval fred = jack.copy(name = \"Fred\")\nfred: Person(name=Fred, age=42)<\/pre>\n<p>\u6b64\u5916\uff0c\u5e94\u5c3d\u53ef\u80fd\u4e3a\u9886\u57df\u76f8\u5173\u7684\u7c7b\u4f7f\u7528 data \u7c7b\u3002 \u5b83\u4eec\u7684\u4e0d\u53ef\u53d8\u7279\u6027\u53ef\u4ee5\u786e\u4fdd\u5728\u5904\u7406\u5e94\u7528\u7a0b\u5e8f\u6838\u5fc3\u903b\u8f91\u65f6\uff0c\u63d0\u4f9b\u5b89\u5168\u3001\u7b80\u6d01\u3001\u65e0\u5fe7\u7684\u4f53\u9a8c\u3002<\/p>\n<p>\u5efa\u8bae\uff1a<strong>\u4f18\u5148\u4f7f\u7528\u4e0d\u53ef\u53d8\u96c6\u5408\u800c\u975e\u53ef\u53d8\u96c6\u5408<\/strong><\/p>\n<p>\u4e0d\u53ef\u53d8\u96c6\u5408\u5728\u7ebf\u7a0b\u5b89\u5168\u65b9\u9762\u5177\u6709\u663e\u8457\u4f18\u52bf\uff0c\u4e0d\u4ec5\u53ef\u4ee5\u5b89\u5168\u5730\u4f20\u9012\uff0c\u800c\u4e14\u66f4\u6613\u4e8e\u7406\u89e3\u3002 \u5c3d\u7ba1 Java \u96c6\u5408\u4e3a\u96c6\u5408\u63d0\u4f9b\u4e86\u4e00\u4e9b\u4e0d\u53ef\u53d8\u7279\u6027\uff0c\u4f46\u5176\u4f7f\u7528\u5b58\u5728\u98ce\u9669\uff0c\u56e0\u4e3a\u8fd9\u5f88\u5bb9\u6613\u5728\u8fd0\u884c\u65f6\u5f15\u53d1\u5f02\u5e38\uff1a<\/p>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">List.of(1,2,3).add(4); \u274cunsafe \ud83d\ude2c! .add(...) compiles, but throws UnsupportedOperationException<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/The default collections in Kotlin are immutable (read-only)\nlistOf(1,2,3).add(4); \u00a0\/\/\u2705safe: does not compile\n\nval l0 = listOf(1,2,3)\u00a0\nval l1 = l0 + 4 \/\/\u2705safe: it will return a new list containing the added element\nl1 shouldBe listOf(1,2,3,4) \/\/\u2705<\/pre>\n<p>\u4f7f\u7528 <code>Collections.<em>unmodifiableList(...)<\/em><\/code> \u4e5f\u662f\u5982\u6b64\uff0c\u5b83\u4eec\u4e0d\u4ec5\u4e0d\u5b89\u5168\uff0c\u8fd8\u9700\u8981\u989d\u5916\u5206\u914d\u5185\u5b58\uff1a<\/p>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class PersonRepo {\n\u00a0\u00a0\u00a0private final List cache = new ArrayList();\n\u00a0\u00a0\u00a0\/\/ Java \u2013 must clone or wrap every call\n\u00a0\u00a0\u00a0public List getItems() {\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return Collections.unmodifiableList(cache); \u00a0 \/\/\u26a0\ufe0fextra alloc\n\u00a0\u00a0\u00a0}\n}\n\n\/\/Usage\npersonRepo.getItems().add(joe) \u274cunsafe \ud83d\ude2c! .add(...) can be called but throws UnsupportedOperationException<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class PersonRepo {\n\n\/\/The need to type \u2018mutable\u2019 for mutable collections is intentional: Kotlin wants you to use immutable ones by default. But sometimes you need them:\n\n\u00a0\u00a0\u00a0private val cache: MutableList = mutableListOf()\n\n\u00a0\u00a0\u00a0fun items(): List = cache \/\/\u2705safe: though the underlying collection is mutable, by returning it as its superclass List, it only exposes the read-only interface\n\n}\n\n\/\/Usage\npersonRepo.items().add(joe) \/\/\u2705safe:\ud83d\ude2c! Does not compile<\/pre>\n<p>\u5728\u5e76\u53d1\u573a\u666f\u4e2d\uff0c\u5e94\u4f18\u5148\u4f7f\u7528\u4e0d\u53ef\u53d8\u6570\u636e\u7ed3\u6784\uff0c\u5305\u62ec\u96c6\u5408\u3002 \u5728 Java \u4e2d\uff0c\u8fd9\u9700\u8981\u989d\u5916\u8d39\u529b\u4f7f\u7528\u4e00\u4e9b\u7279\u6b8a\u7684\u96c6\u5408\uff0c\u8fd9\u4e9b\u96c6\u5408\u63d0\u4f9b\u7684 API \u8981\u4e48\u4e0d\u540c\uff0c\u8981\u4e48\u53d7\u9650\uff0c\u4f8b\u5982 <code>CopyOnWriteArrayList<\/code>\u3002 \u53e6\u4e00\u65b9\u9762\uff0c\u5728 Kotlin \u4e2d\uff0c\u53ea\u8bfb\u7684 <code>List<\/code> \u51e0\u4e4e\u80fd\u6ee1\u8db3\u6240\u6709\u7528\u4f8b\u7684\u9700\u6c42\u3002<\/p>\n<p>\u5982\u679c\u9700\u8981\u53ef\u53d8\u4e14\u7ebf\u7a0b\u5b89\u5168\u7684\u96c6\u5408\uff0cKotlin \u63d0\u4f9b\u4e86\u6301\u4e45\u5316\u96c6\u5408\uff08<code>persistentListOf(...)<\/code>\u3001<code>persistentMapOf(...)<\/code>\uff09\uff0c\u5b83\u4eec\u90fd\u5171\u7528\u540c\u4e00\u4e2a\u5f3a\u5927\u7684\u63a5\u53e3\u3002<\/p>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">ConcurrentHashMap persons = new ConcurrentHashMap();\npersons.put(\"Alice\", 23);\npersons.put(\"Bob\", \u00a0 21);\n\n\/\/not fluent and data copying going on\nMap incPersons = new HashMap(persons.size());\npersons.forEach((k, v) -&gt; incPersons.put(k, v + 1));\n\n\/\/wordy and data copying going on\npersons\n\u00a0\u00a0\u00a0.entrySet()\n\u00a0\u00a0\u00a0.stream()\n\u00a0\u00a0\u00a0.forEach(entry -&gt;\u00a0\n      entry.setValue(entry.getValue() + 1));<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">persistentMapOf(\"Alice\" to 23, \"Bob\" to 21)\n\u00a0\u00a0\u00a0      .mapValues { (key, value) -&gt; value + 1 } \/\/\u2705same rich API like any other Kotlin Map type and not data copying going on<\/pre>\n<h4 class=\"wp-block-heading\"><em>\u9677\u9631 7\uff1a\u6301\u7eed\u4f7f\u7528\u6784\u5efa\u5668\uff08\u66f4\u7cdf\u7684\u662f\uff1a\u5c1d\u8bd5\u4f7f\u7528 Lombok\uff09\u00a0<\/em><\/h4>\n<p>\u5efa\u8bae\uff1a<strong>\u4f7f\u7528\u547d\u540d\u5b9e\u53c2<\/strong>\u3002<\/p>\n<p>\u6784\u5efa\u5668\u5728 Java \u4e2d\u5341\u5206\u5e38\u89c1\u3002 \u5c3d\u7ba1\u6784\u5efa\u5668\u4f7f\u7528\u8d77\u6765\u5f88\u65b9\u4fbf\uff0c\u4f46\u5b83\u4eec\u4f1a\u589e\u52a0\u989d\u5916\u4ee3\u7801\u3001\u5b58\u5728\u5b89\u5168\u9690\u60a3\uff0c\u8fd8\u4f1a\u589e\u52a0\u590d\u6742\u6027\u3002 \u5728 Kotlin \u4e2d\uff0c\u6784\u5efa\u5668\u6beb\u65e0\u7528\u6b66\u4e4b\u5730\uff0c\u56e0\u4e3a\u4e00\u4e2a\u7b80\u5355\u7684\u8bed\u8a00\u529f\u80fd\u5c31\u4f7f\u5176\u6ca6\u4e3a\u591a\u4f59\uff1a\u547d\u540d\u5b9e\u53c2\u3002<\/p>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">public record Person(String name, int age) {\n\n\u00a0\u00a0\u00a0\/\/ Builder for Person\n\u00a0\u00a0\u00a0public static class Builder {\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0private String name;\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0private int age;\n\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0public Builder() {}\n\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0public Builder name(String name) {\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0this.name = name;\n\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return this;\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}\n\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0public Builder age(int age) {\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0this.age = age;\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return this;\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}\n\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0public Person build() {\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return new Person(name, age);\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}\n\u00a0\u00a0\u00a0}\n}\n\n\/\/Usage\nnew JPerson.Builder().name(\"Jack\").age(36).build(); \/\/compiles and succeeds at runtime\n\nnew JPerson.Builder().age(36).build(); \/\/\u274cunsafe \ud83d\ude2c: compiles but fails at runtime.<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">data class Person(val name: String, val age: Int = 0)\n\n\/\/Usage - no builder, only named arguments.\nPerson(name = \"Jack\") \/\/\u2705safe: if it compiles, it always succeeds at runtime\nPerson(name = \"Jack\", age = 36) \/\/\u2705<\/pre>\n<h3 id=\"2.-extend\/convert-an-existing-java-application\" class=\"wp-block-heading\"><strong>2. \u6269\u5c55\/\u8f6c\u6362\u73b0\u6709\u7684 Java \u5e94\u7528\u7a0b\u5e8f<\/strong><\/h3>\n<p>\u5982\u679c\u6ca1\u6709\u4ece\u96f6\u5f00\u59cb\u5c1d\u8bd5 Kotlin \u7684\u6761\u4ef6\uff0c\u4e0d\u59a8<a href=\"https:\/\/www.jetbrains.com.cn\/help\/idea\/get-started-with-kotlin.html#add-kotlin-dependency\" target=\"_blank\" rel=\"noreferrer noopener\">\u5728\u73b0\u6709 Java \u4ee3\u7801\u5e93\u4e2d\u6dfb\u52a0\u65b0\u7684 Kotlin \u529f\u80fd\u6216\u5b8c\u6574\u7684 Kotlin \u6a21\u5757<\/a>\u3002 \u5f97\u76ca\u4e8e Kotlin \u4e0e Java \u7684\u65e0\u7f1d\u4e92\u64cd\u4f5c\u6027\uff0c\u60a8\u7f16\u5199\u7684 Kotlin \u4ee3\u7801\u5bf9 Java \u8c03\u7528\u8005\u800c\u8a00\u53ef\u4ee5\u50cf Java \u4ee3\u7801\u4e00\u6837\u3002 \u8fd9\u79cd\u65b9\u5f0f\u53ef\u4ee5\u5b9e\u73b0\u4ee5\u4e0b\u76ee\u7684\uff1a<\/p>\n<ul>\n<li>\u65e0\u9700\u5927\u89c4\u6a21\u91cd\u5199\u5373\u53ef\u9010\u6b65\u8fc1\u79fb<\/li>\n<li>\u5728\u7279\u5b9a\u573a\u666f\u4e2d\u5bf9 Kotlin \u8fdb\u884c\u5b9e\u9645\u6d4b\u8bd5<\/li>\n<li>\u901a\u8fc7\u751f\u4ea7\u7ea7 Kotlin \u4ee3\u7801\u5efa\u7acb\u56e2\u961f\u4fe1\u5fc3<\/li>\n<\/ul>\n<p>\u4e0e\u5176<em>\u6f2b\u65e0\u76ee\u7684<\/em>\u5730\u5f00\u59cb\uff0c\u4e0d\u59a8\u8003\u8651\u4ee5\u4e0b\u8fd9\u4e9b\u4e0d\u540c\u65b9\u5f0f\uff1a<\/p>\n<p><strong>\u7531\u5916\u800c\u5185\uff1a<\/strong><\/p>\n<p>\u4ece\u5e94\u7528\u7a0b\u5e8f\u7684\u201c\u53f6\u5b50\u201d\u90e8\u5206\uff08\u4f8b\u5982\uff0c\u63a7\u5236\u5668\u3001\u6279\u5904\u7406\u4f5c\u4e1a\u7b49\uff09\u5f00\u59cb\uff0c\u7136\u540e\u9010\u6b65\u5411\u6838\u5fc3\u9886\u57df\u63a8\u8fdb\u3002 \u8fd9\u79cd\u65b9\u5f0f\u5177\u6709\u4ee5\u4e0b\u4f18\u52bf\uff1a<\/p>\n<ul>\n<li><strong>\u7f16\u8bd1\u65f6\u9694\u79bb<\/strong>\u3002\u53f6\u5b50\u7c7b\u5f88\u5c11\u88ab\u5176\u4ed6\u7ec4\u4ef6\u4f9d\u8d56\uff0c\u56e0\u6b64\u60a8\u53ef\u4ee5\u5c06\u5176\u8f6c\u6362\u4e3a Kotlin\uff0c\u800c\u7cfb\u7edf\u5176\u4f59\u90e8\u5206\u4ecd\u80fd\u4fdd\u6301\u4e0d\u53d8\u5e76\u6b63\u5e38\u6784\u5efa\u3002<\/li>\n<li><strong>\u51cf\u5c11\u8fde\u9501\u7f16\u8f91<\/strong>\u3002 \u501f\u52a9\u65e0\u7f1d\u7684\u4e92\u64cd\u4f5c\u6027\uff0c\u8f6c\u6362\u540e\u7684 UI\/\u63a7\u5236\u5668\u8c03\u7528\u73b0\u6709 Java \u9886\u57df\u4ee3\u7801\u65f6\u51e0\u4e4e\u65e0\u9700\u66f4\u6539\u3002<\/li>\n<li><strong>\u66f4\u5c0f\u7684\u62c9\u53d6\u8bf7\u6c42\uff0c\u66f4\u7b80\u5355\u7684\u5ba1\u67e5<\/strong>\u3002 \u53ef\u4ee5\u6309\u6587\u4ef6\u6216\u6309\u529f\u80fd\u9010\u6b65\u8fc1\u79fb\u3002<\/li>\n<\/ul>\n<p><strong>\u7531\u5185\u800c\u5916\uff1a<\/strong><\/p>\n<p>\u4ece\u6838\u5fc3\u90e8\u5206\u7740\u624b\uff0c\u518d\u9010\u6b65\u63a8\u8fdb\u5230\u5916\u5c42\uff0c\u8fd9\u79cd\u65b9\u5f0f\u5f80\u5f80\u98ce\u9669\u66f4\u9ad8\uff0c\u56e0\u4e3a\u5b83\u4f1a\u524a\u5f31\u524d\u6587\u63d0\u5230\u7684\u201c\u7531\u5916\u800c\u5185\u201d\u65b9\u5f0f\u7684\u4f18\u52bf\u3002 \u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u4ee5\u4e0b\u60c5\u51b5\uff0c\u8fd9\u4ecd\u662f\u4e00\u79cd\u53ef\u884c\u7684\u9009\u62e9\uff1a<\/p>\n<ul>\n<li><strong>\u6838\u5fc3\u90e8\u5206\u975e\u5e38\u5c0f\u6216\u81ea\u6210\u4f53\u7cfb<\/strong>\u3002 \u5982\u679c\u9886\u57df\u5c42\u53ea\u6709\u5c11\u91cf POJO \u548c\u670d\u52a1\uff0c\u5c3d\u65e9\u8f6c\u6362\u53ef\u80fd\u6210\u672c\u8f83\u4f4e\uff0c\u8fd8\u80fd\u7acb\u5373\u89e3\u9501\u7b26\u5408\u4e60\u60ef\u7684\u6784\u9020\uff08data \u7c7b\u3001\u503c\u7c7b\u3001\u5bc6\u5c01\u5c42\u6b21\u7ed3\u6784\uff09\u3002<\/li>\n<li><strong>\u672c\u8eab\u5c31\u8981\u8fdb\u884c\u67b6\u6784\u91cd\u6784<\/strong>\u3002 \u5982\u679c\u8ba1\u5212\u5728\u8fc1\u79fb\u7684\u540c\u65f6\u91cd\u6784\u4e0d\u53d8\u91cf\u6216\u5f15\u5165 DDD \u6a21\u5f0f\uff08\u503c\u5bf9\u8c61\u3001\u805a\u5408\uff09\uff0c\u6709\u65f6\u5148\u5728 Kotlin \u4e2d\u91cd\u65b0\u8bbe\u8ba1\u9886\u57df\u5c42\u4f1a\u66f4\u6574\u6d01\u3002<\/li>\n<li><strong>\u4e25\u683c\u7684 null \u5b89\u5168\u7ea6\u5b9a<\/strong>\u3002 \u5c06 Kotlin \u7f6e\u4e8e\u6838\u5fc3\u4f4d\u7f6e\uff0c\u53ef\u4ee5\u5c06\u9886\u57df\u5c42\u6253\u9020\u6210\u4e00\u5ea7\u201c null \u5b89\u5168\u5821\u5792\u201d\uff1b\u5916\u5c42\u7684 Java \u4ee3\u7801\u4ecd\u53ef\u80fd\u4f20\u5165 null \u503c\uff0c\u4f46\u8fb9\u754c\u4f1a\u53d8\u5f97\u6e05\u6670\u660e\u786e\uff0c\u4e5f\u66f4\u6613\u4e8e\u7ba1\u63a7\u3002<\/li>\n<\/ul>\n<p><strong>\u9010\u4e2a\u6a21\u5757\u8fdb\u884c<\/strong><\/p>\n<ul>\n<li>\u5982\u679c\u60a8\u7684\u67b6\u6784\u662f\u6309\u529f\u80fd\u800c\u975e\u6309\u5c42\u7ec4\u7ec7\u7684\uff0c\u4e14\u6a21\u5757\u89c4\u6a21\u53ef\u63a7\uff0c\u5219\u4e0d\u59a8\u9010\u4e2a\u8f6c\u6362\u6a21\u5757\u3002<\/li>\n<\/ul>\n<p><strong>\u7528\u4e8e\u5c06 Java \u8f6c\u6362\u4e3a Kotlin \u7684\u8bed\u8a00\u529f\u80fd<\/strong><\/p>\n<p>Kotlin \u63d0\u4f9b\u4e86\u591a\u79cd\u529f\u80fd\uff08\u4e3b\u8981\u662f\u6ce8\u89e3\uff09\uff0c\u80fd\u8ba9\u60a8\u7684 Kotlin \u4ee3\u7801\u8868\u73b0\u5f97\u5982\u540c\u539f\u751f Java \u4ee3\u7801\u4e00\u822c\u3002 \u5728 Kotlin \u4e0e Java \u5171\u5b58\u4e8e\u540c\u4e00\u4ee3\u7801\u5e93\u7684\u6df7\u5408\u73af\u5883\u4e2d\uff0c\u8fd9\u4e00\u70b9\u7684\u4ef7\u503c\u5c24\u4e3a\u7a81\u51fa\u3002<br \/>\n<strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class Person @JvmOverloads constructor(val name: String,\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 var age: Int = 0) {\n\u00a0 companion object {\n\n\u00a0 @JvmStatic\n\u00a0 @Throws(InvalidNameException::class)\n\u00a0 fun newBorn(name: String): Person = if (name.isEmpty())\u00a0\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0throw InvalidNameException(\"name not set\")\n\u00a0\u00a0\u00a0\u00a0\u00a0else Person(name, 0)\n\n\u00a0\u00a0\u00a0@JvmField\n\u00a0\u00a0\u00a0val LOG = LoggerFactory.getLogger(KPerson.javaClass)\n\u00a0\u00a0}\n}<\/pre>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/thanks to @JvmOverloads an additional constructor is created, propagating Kotlin\u2019s default arguments to Java\nvar john =\u00a0 new Person(\"John\");\n\n\/\/Kotlin automatically generates getters (val) and setters (var) for Java\njohn.setAge(23);\nvar name = ken.getName();\n\n\/\/@JvmStatic and @JvmField all accessing (companion) object fields and methods as statics in Java\n\n\/\/Without @JvmStatic it would be: Person.Companion.newBorn(...)\nvar ken =\u00a0 Person.newBorn(\"Ken\");\u00a0\n\n\/\/Without @JvmField it would be: Person.Companion.LOG\nPerson.LOG.info(\"Hello World, Ken ;-)\");\n\n\/\/@Throws(...) will put the checked Exception in the method signature \ntry {\n\u00a0 Person ken =\u00a0 Person.newBorn(\"Ken\");\n} catch (InvalidNameException e) {\n\u00a0 \/\/\u2026\n}<\/pre>\n<p><strong>Kotlin<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"kotlin\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">@file:JvmName(\"Persons\")\npackage org.abc\n\n@JvmName(\"prettyPrint\")\n\nfun Person.pretty() =\n\u00a0 \u00a0 \u00a0 Person.LOG.info(\"$name is $age old\")<\/pre>\n<p><strong>Java<\/strong><\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/@JvmName for files and methods makes accessing static fields look like Java: without it would be: PersonKt.pretty(...)\nPersons.prettyPrint(ken)<\/pre>\n<p><strong>IntelliJ IDEA \u7684 Java \u8f6c Kotlin \u8f6c\u6362\u5668<\/strong><\/p>\n<p>IntelliJ IDEA \u63d0\u4f9b\u4e86 Java \u8f6c Kotlin \u8f6c\u6362\u5668\uff0c\u7406\u8bba\u4e0a\uff0c\u8be5\u5de5\u5177\u53ef\u4ee5\u81ea\u52a8\u5b8c\u6210\u8f6c\u6362\u5de5\u4f5c\u3002 \u4e0d\u8fc7\uff0c\u8f6c\u6362\u751f\u6210\u7684\u4ee3\u7801\u5f80\u5f80\u4e0d\u591f\u7406\u60f3\uff0c\u56e0\u6b64\u5efa\u8bae\u4ec5\u5c06\u5176\u4f5c\u4e3a\u8d77\u70b9\u3002 \u5728\u6b64\u57fa\u7840\u4e0a\uff0c\u8fd8\u9700\u8fdb\u4e00\u6b65\u5c06\u4ee3\u7801\u6253\u78e8\u6210\u66f4\u5730\u9053\u7684 Kotlin \u98ce\u683c\u3002 \u672c\u535a\u6587\u7cfb\u5217\u7684\u6700\u540e\u4e00\u7bc7<em>\u5927\u89c4\u6a21\u91c7\u7528 Kotlin \u7684\u6210\u529f\u56e0\u7d20<\/em>\u5c06\u6df1\u5165\u63a2\u8ba8\u6b64\u4e3b\u9898\u3002<\/p>\n<p>\u5982\u679c\u4ee5 Java \u4e3a\u8d77\u70b9\uff0c\u5199\u51fa\u7684 Kotlin \u4ee3\u7801\u5f88\u53ef\u80fd\u5e26\u7740 Java \u7684\u5f71\u5b50\u3002 \u8fd9\u7c7b\u4ee3\u7801\u867d\u80fd\u5e26\u6765\u4e00\u4e9b\u597d\u5904\uff0c\u4f46\u65e0\u6cd5\u5145\u5206\u91ca\u653e Kotlin \u7684\u6f5c\u529b\u3002 \u56e0\u6b64\uff0c\u6211\u66f4\u503e\u5411\u4e8e\u7f16\u5199\u65b0\u5e94\u7528\u7a0b\u5e8f\u8fd9\u79cd\u65b9\u5f0f\u3002<\/p>\n<h3 class=\"wp-block-heading\">\u7cfb\u5217\u535a\u6587\u540e\u7eed\u5185\u5bb9<\/h3>\n<p>\u5728<em>\u5728\u4ee5 Java \u4e3a\u4e3b\u7684\u73af\u5883\u4e2d\u6210\u529f\u91c7\u7528 Kotlin \u7684\u7ec8\u6781\u6307\u5357<\/em>\u7cfb\u5217\u535a\u6587\u7684\u8fd9\u4e00\u7bc7\u4e2d\uff0c\u6211\u4eec\u4ecb\u7ecd\u4e86 Kotlin \u5b9e\u9a8c\u5982\u4f55\u9010\u6b65\u53d1\u5c55\u4e3a\u751f\u4ea7\u7ea7\u4ee3\u7801\u3002 \u6211\u4eec\u7684\u4e0b\u4e00\u7bc7\u535a\u6587\u5c06\u805a\u7126\u4e8e Kotin \u91c7\u7528\u7684\u4eba\u6587\u5c42\u9762\uff1a\u8bf4\u670d\u540c\u4e8b\u3002 \u6587\u4e2d\u5c06\u4ecb\u7ecd\u5982\u4f55\u7528\u6e05\u6670\u4e14\u4ee5\u4ee3\u7801\u4e3a\u4f9d\u636e\u7684\u8bba\u636e\u8fdb\u884c\u9610\u8ff0\u3001\u5982\u4f55\u6307\u5bfc\u65b0\u52a0\u5165\u7684\u5f00\u53d1\u8005\uff0c\u4ee5\u53ca\u5982\u4f55\u5728\u56e2\u961f\u5185\u90e8\u5efa\u7acb\u4e00\u4e2a\u89c4\u6a21\u867d\u5c0f\u5374\u80fd\u6301\u7eed\u53d1\u5c55\u7684 Kotlin \u793e\u533a\u3002<\/p>\n<div class=\"about-author \">\n<div class=\"about-author__box\">\n<div class=\"row\">\n<div class=\"about-author__box-img\"><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2025\/10\/a3f7-400o400o1-QYUavRYyARnAVJLCpM1m8M.webp\" alt=\"\" \/><\/div>\n<div class=\"about-author__box-text\">\n<h4>Urs Peter<\/h4>\n<p>Urs \u662f\u4e00\u4f4d\u7ecf\u9a8c\u4e30\u5bcc\u7684\u8f6f\u4ef6\u5de5\u7a0b\u5e08\u3001\u89e3\u51b3\u65b9\u6848\u67b6\u6784\u5e08\u3001\u4f1a\u8bae\u6f14\u8bb2\u5609\u5bbe\u548c\u57f9\u8bad\u5e08\uff0c\u5728\u6784\u5efa\u5f39\u6027\u3001\u53ef\u6269\u7f29\u548c\u4efb\u52a1\u5173\u952e\u578b\u7cfb\u7edf\u65b9\u9762\u62e5\u6709 20 \u4f59\u5e74\u7684\u4e30\u5bcc\u7ecf\u9a8c\uff0c\u4e3b\u8981\u6d89\u53ca Kotlin \u548c Scala\u3002<\/p>\n<p>\u9664\u4e86\u62c5\u4efb\u987e\u95ee\u4e4b\u5916\uff0c\u4ed6\u8fd8\u662f\u4e00\u4f4d\u5145\u6ee1\u70ed\u60c5\u7684\u57f9\u8bad\u5e08\uff0c\u5e76\u64b0\u5199\u4e86\u4e30\u5bcc\u591a\u6837\u7684\u8bfe\u7a0b\uff0c\u6d89\u53ca\u4ece Kotlin \u548c Scala \u8bed\u8a00\u8bfe\u7a0b\u5230\u5fae\u670d\u52a1\u548c\u4e8b\u4ef6\u9a71\u52a8\u578b\u67b6\u6784\u7b49\u67b6\u6784\u57f9\u8bad\u7684\u4f17\u591a\u5185\u5bb9\u3002<\/p>\n<p>\u4f5c\u4e3a\u5929\u751f\u793e\u4ea4\u8fbe\u4eba\uff0c\u4ed6\u559c\u6b22\u5728\u805a\u4f1a\u548c\u4f1a\u8bae\u4e0a\u5206\u4eab\u77e5\u8bc6\uff0c\u542f\u53d1\u540c\u884c\u5e76\u83b7\u5f97\u540c\u884c\u542f\u53d1\u3002 Urs \u662f\u4e00\u4f4d JetBrains \u8ba4\u8bc1 Kotlin \u57f9\u8bad\u5e08\u3002<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"author":1297,"featured_media":653622,"comment_status":"closed","ping_status":"closed","template":"","categories":[],"tags":[],"cross-post-tag":[],"acf":[],"_links":{"self":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/kotlin\/657571"}],"collection":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/kotlin"}],"about":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/types\/kotlin"}],"author":[{"embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/users\/1297"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/comments?post=657571"}],"version-history":[{"count":2,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/kotlin\/657571\/revisions"}],"predecessor-version":[{"id":657574,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/kotlin\/657571\/revisions\/657574"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/media\/653622"}],"wp:attachment":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/media?parent=657571"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/categories?post=657571"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/tags?post=657571"},{"taxonomy":"cross-post-tag","embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/cross-post-tag?post=657571"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}