{"id":3883,"date":"2025-07-12T13:51:49","date_gmt":"2025-07-12T05:51:49","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=3883"},"modified":"2025-07-12T13:51:49","modified_gmt":"2025-07-12T05:51:49","slug":"volatile%e5%85%b3%e9%94%ae%e5%ad%97%e6%9c%89%e4%bb%80%e4%b9%88%e7%94%a8%ef%bc%9f%e5%ae%83%e7%9a%84%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86%e6%98%af%e4%bb%80%e4%b9%88%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/07\/12\/volatile%e5%85%b3%e9%94%ae%e5%ad%97%e6%9c%89%e4%bb%80%e4%b9%88%e7%94%a8%ef%bc%9f%e5%ae%83%e7%9a%84%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86%e6%98%af%e4%bb%80%e4%b9%88%ef%bc%9f\/","title":{"rendered":"volatile\u5173\u952e\u5b57\u6709\u4ec0\u4e48\u7528\uff1f\u5b83\u7684\u5b9e\u73b0\u539f\u7406\u662f\u4ec0\u4e48\uff1f"},"content":{"rendered":"\n<p><code>volatile<\/code> \u662f Java \u5e76\u53d1\u7f16\u7a0b\u4e2d\u7684\u4e00\u4e2a\u5173\u952e\u5b57\uff0c\u5b83\u770b\u8d77\u6765\u7b80\u5355\uff0c\u5b9e\u5219\u6d89\u53ca JVM\u3001\u5185\u5b58\u6a21\u578b\uff08JMM\uff09\u3001\u6c47\u7f16\u6307\u4ee4\u3001\u7f16\u8bd1\u5668\u4f18\u5316\u7b49\u591a\u4e2a\u5e95\u5c42\u673a\u5236\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e00\u3001volatile \u7684\u4f5c\u7528<\/h2>\n\n\n\n<p><code>volatile<\/code> \u662f Java \u63d0\u4f9b\u7684\u4e00\u79cd<strong>\u8f7b\u91cf\u7ea7\u7684\u540c\u6b65\u673a\u5236<\/strong>\uff0c\u7528\u4e8e<strong>\u786e\u4fdd\u5171\u4eab\u53d8\u91cf\u7684\u53ef\u89c1\u6027\u548c\u7981\u6b62\u6307\u4ee4\u91cd\u6392\u5e8f<\/strong>\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e8c\u3001volatile \u7684\u4e24\u4e2a\u6838\u5fc3\u4f5c\u7528<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u4f5c\u7528<\/th><th>\u8bf4\u660e<\/th><\/tr><\/thead><tbody><tr><td>\u2705 <strong>\u53ef\u89c1\u6027\uff08visibility\uff09<\/strong><\/td><td>\u4fdd\u8bc1\u4e00\u4e2a\u7ebf\u7a0b\u5bf9\u53d8\u91cf\u7684\u4fee\u6539\uff0c<strong>\u80fd\u88ab\u5176\u4ed6\u7ebf\u7a0b\u7acb\u5373\u770b\u5230<\/strong><\/td><\/tr><tr><td>\u2705 <strong>\u7981\u6b62\u6307\u4ee4\u91cd\u6392\u5e8f\uff08ordering\uff09<\/strong><\/td><td>\u4fdd\u8bc1\u53d8\u91cf\u7684\u5199\u64cd\u4f5c <strong>\u4e0d\u4f1a\u4e0e\u524d\u540e\u4ee3\u7801\u91cd\u6392\u5e8f<\/strong>\uff0c\u9002\u7528\u4e8e\u591a\u7ebf\u7a0b\u573a\u666f\u4e2d\u7684\u201chappen-before\u201d\u539f\u5219<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u26a0\ufe0f \u6ce8\u610f\uff1a<strong><code>volatile<\/code> \u4e0d\u80fd\u4fdd\u8bc1\u539f\u5b50\u6027\uff01<\/strong>\uff08\u5373 ++ \u64cd\u4f5c\u4ecd\u7136\u53ef\u80fd\u5e76\u53d1\u51b2\u7a81\uff09<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e09\u3001\u4ec0\u4e48\u65f6\u5019\u4f7f\u7528 volatile\uff1f<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u72b6\u6001\u6807\u5fd7\u53d8\u91cf<\/strong>\uff1a\u5982\u505c\u6b62\u6807\u8bb0 <code>volatile boolean running = true;<\/code><\/li>\n\n\n\n<li><strong>\u53cc\u91cd\u68c0\u67e5\u9501\uff08DCL\uff09<\/strong>\uff1a\u7528\u4e8e\u5355\u4f8b\u6a21\u5f0f\u4e2d\u7684\u61d2\u52a0\u8f7d\u521d\u59cb\u5316\uff08\u9632\u6b62\u6307\u4ee4\u91cd\u6392\uff09<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u56db\u3001\u4ee3\u7801\u793a\u4f8b<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">\u793a\u4f8b 1\uff1a\u65e0 volatile\uff0c\u51fa\u73b0\u6b7b\u5faa\u73af<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>class Worker extends Thread {\n    private boolean running = true;\n\n    public void run() {\n        while (running) {\n            \/\/ do something\n        }\n        System.out.println(\"Worker stopped.\");\n    }\n\n    public void stopWorker() {\n        running = false;\n    }\n}<\/code><\/pre>\n\n\n\n<p>\u5f53\u4e3b\u7ebf\u7a0b\u8c03\u7528 <code>stopWorker()<\/code> \u540e\uff0c<strong>Worker \u7ebf\u7a0b\u53ef\u80fd\u6c38\u8fdc\u770b\u4e0d\u5230 running = false<\/strong>\uff08\u7f13\u5b58\u95ee\u9898\uff09\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u793a\u4f8b 2\uff1a\u4f7f\u7528 volatile \u4fdd\u8bc1\u53ef\u89c1\u6027<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>private volatile boolean running = true;<\/code><\/pre>\n\n\n\n<p>\u8fd9\u6837\u53ef\u4ee5<strong>\u5f3a\u5236\u6bcf\u6b21\u4ece\u4e3b\u5185\u5b58\u8bfb\u53d6\u53d8\u91cf\u7684\u503c<\/strong>\uff0c\u800c\u4e0d\u662f\u4f7f\u7528\u7ebf\u7a0b\u5c40\u90e8\u7f13\u5b58\uff08\u5982 CPU cache \u6216\u5bc4\u5b58\u5668\u4e2d\u65e7\u503c\uff09\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e94\u3001\u5e95\u5c42\u539f\u7406\uff1a\u5982\u4f55\u5b9e\u73b0\u8fd9\u4e24\u4e2a\u8bed\u4e49\uff1f<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u53ef\u89c1\u6027\u5b9e\u73b0\u673a\u5236<\/h3>\n\n\n\n<p>\u5f53\u4e00\u4e2a\u53d8\u91cf\u88ab\u58f0\u660e\u4e3a <code>volatile<\/code> \u65f6\uff0cJava \u7f16\u8bd1\u5668\u548c\u5904\u7406\u5668\u4f1a\u786e\u4fdd\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5bf9\u8be5\u53d8\u91cf\u7684 <strong>\u5199\u64cd\u4f5c<\/strong>\u4f1a\u7acb\u5373\u5237\u65b0\u5230\u4e3b\u5185\u5b58<\/li>\n\n\n\n<li>\u5bf9\u8be5\u53d8\u91cf\u7684 <strong>\u8bfb\u64cd\u4f5c<\/strong>\u4f1a\u5f3a\u5236\u4ece\u4e3b\u5185\u5b58\u91cd\u65b0\u8bfb\u53d6\u6700\u65b0\u503c<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u7981\u6b62\u6307\u4ee4\u91cd\u6392\u5e8f\u5b9e\u73b0\u673a\u5236<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7f16\u8bd1\u5668\u4f1a\u5728\u751f\u6210\u6307\u4ee4\u65f6\u52a0\u5165\u5185\u5b58\u5c4f\u969c\uff08<strong>Memory Barrier<\/strong>\uff09<\/li>\n\n\n\n<li>CPU \u4f1a\u6839\u636e\u5c4f\u969c\u9650\u5236\u6307\u4ee4\u4e71\u5e8f\u6267\u884c\uff08\u5982\uff1a<code>StoreLoad barrier<\/code>\uff09<\/li>\n<\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>volatile int a = 0;\na = 1;      \/\/ \u7981\u6b62\u4e0e\u524d\u540e\u5199\u5165\u91cd\u6392\u5e8f\nflag = true; \/\/ flag \u4e3a volatile \u53d8\u91cf<\/code><\/pre>\n\n\n\n<p>\u901a\u8fc7\u63d2\u5165\u5185\u5b58\u5c4f\u969c\uff0cJVM \u4fdd\u8bc1\u5728 <code>flag = true<\/code> \u4e4b\u524d\u6240\u6709\u5199\u64cd\u4f5c\uff08\u5982 <code>a = 1<\/code>\uff09\u90fd\u5bf9\u5176\u4ed6\u7ebf\u7a0b\u53ef\u89c1\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u516d\u3001volatile \u4e0e synchronized \u7684\u533a\u522b<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u5bf9\u6bd4\u70b9<\/th><th><code>volatile<\/code><\/th><th><code>synchronized<\/code><\/th><\/tr><\/thead><tbody><tr><td>\u53ef\u89c1\u6027<\/td><td>\u2705 \u6709<\/td><td>\u2705 \u6709<\/td><\/tr><tr><td>\u539f\u5b50\u6027<\/td><td>\u274c \u65e0<\/td><td>\u2705 \u6709\uff08\u4e34\u754c\u533a\u4e92\u65a5\uff09<\/td><\/tr><tr><td>\u91cd\u6392\u5e8f\u7981\u6b62<\/td><td>\u2705 \u7981\u6b62\u5199\u64cd\u4f5c\u7684\u91cd\u6392\u5e8f<\/td><td>\u2705 \u56e0\u4e3a\u6709\u5185\u5b58\u5c4f\u969c<\/td><\/tr><tr><td>\u7ebf\u7a0b\u963b\u585e<\/td><td>\u274c \u4e0d\u4f1a\u963b\u585e<\/td><td>\u2705 \u963b\u585e\u4e34\u754c\u533a<\/td><\/tr><tr><td>\u6027\u80fd\u5f00\u9500<\/td><td>\u4f4e<\/td><td>\u8f83\u9ad8\uff08\u52a0\u9501\/\u89e3\u9501\uff09<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e03\u3001volatile \u7684\u5178\u578b\u5e94\u7528\uff1a\u53cc\u91cd\u68c0\u67e5\u9501\uff08DCL\uff09<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Singleton {\n    private static volatile Singleton instance;\n\n    private Singleton() {}\n\n    public static Singleton getInstance() {\n        if (instance == null) {\n            synchronized(Singleton.class) {\n                if (instance == null) {\n                    instance = new Singleton(); \/\/ \u53ef\u80fd\u91cd\u6392\u5e8f\u95ee\u9898\n                }\n            }\n        }\n        return instance;\n    }\n}<\/code><\/pre>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u2705 <code>volatile<\/code> \u4fdd\u8bc1 <code>instance<\/code> \u521d\u59cb\u5316\u8fc7\u7a0b\u7684\u6709\u5e8f\u6027\u548c\u53ef\u89c1\u6027\u3002<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u516b\u3001JVM \u5c42\u9762\u7684 volatile \u5173\u952e\u5b9e\u73b0\uff08\u4ee5 OpenJDK \u4e3a\u4f8b\uff09<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5728\u5b57\u8282\u7801\u4e2d\uff0c<code>volatile<\/code> \u5bf9\u5e94\u6307\u4ee4\uff1a<\/li>\n\n\n\n<li><strong>\u5199\u5165\u53d8\u91cf\u65f6<\/strong> \u2192 <code>store<\/code> \u64cd\u4f5c\u540e\u52a0 <code>store-store barrier<\/code><\/li>\n\n\n\n<li><strong>\u8bfb\u53d6\u53d8\u91cf\u65f6<\/strong> \u2192 <code>load<\/code> \u64cd\u4f5c\u524d\u52a0 <code>load-load barrier<\/code><\/li>\n\n\n\n<li>OpenJDK \u5e95\u5c42\u901a\u8fc7 <code>Unsafe<\/code> \u7c7b\u4e0e CPU \u5185\u5b58\u5c4f\u969c\u4ea4\u4e92\uff08\u5982 <code>lock prefix<\/code>\uff09<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e5d\u3001\u9762\u8bd5\u5e38\u89c1\u95ee\u9898\u603b\u7ed3<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1. volatile \u80fd\u4e0d\u80fd\u66ff\u4ee3 synchronized\uff1f<\/h3>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u4e0d\u884c\uff01<code>volatile<\/code> \u53ea\u80fd\u4fdd\u8bc1<strong>\u53ef\u89c1\u6027<\/strong>\uff0c\u4e0d\u80fd\u4fdd\u8bc1<strong>\u539f\u5b50\u6027<\/strong>\uff0c\u5982 <code>count++<\/code> \u4ecd\u7136\u4e0d\u5b89\u5168\u3002<\/p>\n<\/blockquote>\n\n\n\n<h3 class=\"wp-block-heading\">2. volatile \u662f\u7ebf\u7a0b\u5b89\u5168\u7684\u5417\uff1f<\/h3>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u4e0d\u662f\uff0c\u9664\u975e\u64cd\u4f5c\u672c\u8eab\u662f\u539f\u5b50\u7684\uff08\u5982 boolean \u72b6\u6001\u5207\u6362\u3001\u5f15\u7528\u66ff\u6362\uff09\u3002<\/p>\n<\/blockquote>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u54ea\u4e9b\u64cd\u4f5c\u5bf9 volatile \u662f\u5b89\u5168\u7684\uff1f<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8d4b\u503c\u5f15\u7528\u7c7b\u578b<\/li>\n\n\n\n<li>\u5199 boolean\u3001int\u3001long\uff0864 \u4f4d JVM \u4e0b\u957f\u6574\u578b\u9700\u8981\u989d\u5916\u6ce8\u610f\uff09<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u5341\u3001\u5b98\u65b9\u6587\u6863\u4e0e\u8d44\u6599<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd17 <a href=\"https:\/\/docs.oracle.com\/javase\/specs\/jls\/se17\/html\/jls-17.html\">Java Memory Model\uff08JMM\uff09\u89c4\u8303<\/a><\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/github.com\/openjdk\/jdk\/blob\/master\/src\/hotspot\/share\/runtime\/orderAccess.hpp\">OpenJDK \u4e2d volatile \u7684\u5b9e\u73b0<\/a><\/li>\n\n\n\n<li>\ud83d\udcd8\u300aJava \u5e76\u53d1\u7f16\u7a0b\u5b9e\u6218\u300b\uff1avolatile \u6df1\u5165\u5206\u6790\u7ae0\u8282<\/li>\n\n\n\n<li>\ud83d\udcd8\u300a\u6df1\u5165\u7406\u89e3 Java \u865a\u62df\u673a\u300b\uff1a\u5185\u5b58\u6a21\u578b\u4e0e\u7ebf\u7a0b\u5b89\u5168\u7ae0\u8282<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u603b\u7ed3\u53e3\u8bc0<\/h2>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>volatile \u660e\u53ef\u89c1\uff0c\u4e0d\u53ef\u539f\u5b50\u83ab\u8bef\u89e3\uff1b\u9002\u5408\u72b6\u6001\u505a\u6807\u8bb0\uff0c\u53cc\u68c0\u9501\u5b83\u6765\u89e3\u3002<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>volatile \u662f Java \u5e76\u53d1\u7f16\u7a0b\u4e2d\u7684\u4e00\u4e2a\u5173\u952e\u5b57\uff0c\u5b83\u770b\u8d77\u6765\u7b80\u5355\uff0c\u5b9e\u5219\u6d89\u53ca JVM\u3001\u5185\u5b58\u6a21\u578b\uff08JMM\uff09\u3001\u6c47 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":3884,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[86],"tags":[],"class_list":["post-3883","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java-"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3883","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=3883"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3883\/revisions"}],"predecessor-version":[{"id":3885,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3883\/revisions\/3885"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/3884"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=3883"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=3883"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=3883"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}