{"id":80,"date":"2023-02-13T10:48:31","date_gmt":"2023-02-13T02:48:31","guid":{"rendered":"https:\/\/www.appblog.cn\/?p=80"},"modified":"2023-02-13T10:48:59","modified_gmt":"2023-02-13T02:48:59","slug":"java-multi-threag-programming-volatile","status":"publish","type":"post","link":"https:\/\/www.appblog.cn\/index.php\/2023\/02\/13\/java-multi-threag-programming-volatile\/","title":{"rendered":"Java\u591a\u7ebf\u7a0b\u7f16\u7a0b\u4e09\uff08volatile\u5173\u952e\u5b57\uff09"},"content":{"rendered":"<ul>\n<li>\u7981\u6b62\u7f16\u8bd1\u5668\u91cd\u6392<\/li>\n<li>\u7981\u7528\u5bc4\u5b58\u5668\uff0c\u80fd\u591f\u5373\u4f7f\u5237\u65b0\u5185\u5b58\u6570\u636e\u66f4\u65b0<\/li>\n<\/ul>\n<p>Java\u8bed\u8a00\u4e2d\u7684<code>volatile<\/code>\u53d8\u91cf\u53ef\u4ee5\u88ab\u770b\u4f5c\u662f\u4e00\u79cd<code>\u7a0b\u5ea6\u8f83\u8f7b\u7684synchronized<\/code>\uff1b\u4e0e<code>synchronized<\/code>\u5757\u76f8\u6bd4\uff0c<code>volatile<\/code>\u53d8\u91cf\u6240\u9700\u7684\u7f16\u7801\u8f83\u5c11\uff0c\u5e76\u4e14\u8fd0\u884c\u65f6\u5f00\u9500\u4e5f\u8f83\u5c11\uff0c\u4f46\u662f\u5b83\u6240\u80fd\u5b9e\u73b0\u7684\u529f\u80fd\u4e5f\u4ec5\u662f<code>synchronized<\/code>\u7684\u4e00\u90e8\u5206\u3002<\/p>\n<p>\u9501\u63d0\u4f9b\u4e86\u4e24\u79cd\u4e3b\u8981\u7279\u6027\uff1a\u4e92\u65a5\uff08mutual exclusion\uff09 \u548c\u53ef\u89c1\u6027\uff08visibility\uff09\u3002\u4e92\u65a5\u5373\u4e00\u6b21\u53ea\u5141\u8bb8\u4e00\u4e2a\u7ebf\u7a0b\u6301\u6709\u67d0\u4e2a\u7279\u5b9a\u7684\u9501\uff0c\u56e0\u6b64\u53ef\u4f7f\u7528\u8be5\u7279\u6027\u5b9e\u73b0\u5bf9\u5171\u4eab\u6570\u636e\u7684\u534f\u8c03\u8bbf\u95ee\u534f\u8bae\uff0c\u8fd9\u6837\uff0c\u4e00\u6b21\u5c31\u53ea\u6709\u4e00\u4e2a\u7ebf\u7a0b\u80fd\u591f\u4f7f\u7528\u8be5\u5171\u4eab\u6570\u636e\u3002\u53ef\u89c1\u6027\u8981\u66f4\u52a0\u590d\u6742\u4e00\u4e9b\uff0c\u5b83\u5fc5\u987b\u786e\u4fdd\u91ca\u653e\u9501\u4e4b\u524d\u5bf9\u5171\u4eab\u6570\u636e\u505a\u51fa\u7684\u66f4\u6539\u5bf9\u4e8e\u968f\u540e\u83b7\u5f97\u8be5\u9501\u7684\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u662f\u53ef\u89c1\u7684\u3002\u5982\u679c\u6ca1\u6709\u540c\u6b65\u673a\u5236\u63d0\u4f9b\u7684\u8fd9\u79cd\u53ef\u89c1\u6027\u4fdd\u8bc1\uff0c\u7ebf\u7a0b\u770b\u5230\u7684\u5171\u4eab\u53d8\u91cf\u53ef\u80fd\u662f\u4fee\u6539\u524d\u7684\u503c\u6216\u4e0d\u4e00\u81f4\u7684\u503c\uff0c\u8fd9\u5c06\u5f15\u53d1\u8bb8\u591a\u4e25\u91cd\u95ee\u9898\u3002<\/p>\n<h2>volatile \u53d8\u91cf<\/h2>\n<p><code>volatile<\/code>\u53d8\u91cf\u5177\u6709<code>synchronized<\/code>\u7684\u53ef\u89c1\u6027\u7279\u6027\uff0c\u4f46\u662f\u4e0d\u5177\u5907\u539f\u5b50\u7279\u6027\u3002\u8fd9\u5c31\u662f\u8bf4\u7ebf\u7a0b\u80fd\u591f\u81ea\u52a8\u53d1\u73b0<code>volatile<\/code>\u53d8\u91cf\u7684\u6700\u65b0\u503c\u3002<code>volatile<\/code>\u53d8\u91cf\u53ef\u7528\u4e8e\u63d0\u4f9b\u7ebf\u7a0b\u5b89\u5168\uff0c\u4f46\u662f\u53ea\u80fd\u5e94\u7528\u4e8e\u975e\u5e38\u6709\u9650\u7684\u4e00\u7ec4\u7528\u4f8b\uff1a\u591a\u4e2a\u53d8\u91cf\u4e4b\u95f4\u6216\u8005\u67d0\u4e2a\u53d8\u91cf\u7684\u5f53\u524d\u503c\u4e0e\u4fee\u6539\u540e\u503c\u4e4b\u95f4\u6ca1\u6709\u7ea6\u675f\u3002\u56e0\u6b64\uff0c\u5355\u72ec\u4f7f\u7528<code>volatile<\/code>\u8fd8\u4e0d\u8db3\u4ee5\u5b9e\u73b0\u8ba1\u6570\u5668\u3001\u4e92\u65a5\u9501\u6216\u4efb\u4f55\u5177\u6709\u4e0e\u591a\u4e2a\u53d8\u91cf\u76f8\u5173\u7684\u4e0d\u53d8\u5f0f\uff08Invariants\uff09\u7684\u7c7b\uff08\u4f8b\u5982<code>start &lt;= end<\/code>\uff09\u3002<\/p>\n<p>\u51fa\u4e8e\u7b80\u6613\u6027\u6216\u53ef\u4f38\u7f29\u6027\u7684\u8003\u8651\uff0c\u6211\u4eec\u53ef\u80fd\u503e\u5411\u4e8e\u4f7f\u7528<code>volatile<\/code>\u53d8\u91cf\u800c\u4e0d\u662f\u9501\u3002\u5f53\u4f7f\u7528<code>volatile<\/code>\u53d8\u91cf\u800c\u975e\u9501\u65f6\uff0c\u67d0\u4e9b\u4e60\u60ef\u7528\u6cd5\uff08idiom\uff09\u66f4\u52a0\u6613\u4e8e\u7f16\u7801\u548c\u9605\u8bfb\u3002\u6b64\u5916\uff0c<code>volatile<\/code>\u53d8\u91cf\u4e0d\u4f1a\u50cf\u9501\u90a3\u6837\u9020\u6210\u7ebf\u7a0b\u963b\u585e\uff0c\u56e0\u6b64\u4e5f\u5f88\u5c11\u9020\u6210\u53ef\u4f38\u7f29\u6027\u95ee\u9898\u3002\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\uff0c\u5982\u679c\u8bfb\u64cd\u4f5c\u8fdc\u8fdc\u5927\u4e8e\u5199\u64cd\u4f5c\uff0c<code>volatile<\/code>\u53d8\u91cf\u8fd8\u53ef\u4ee5\u63d0\u4f9b\u4f18\u4e8e\u9501\u7684\u6027\u80fd\u4f18\u52bf\u3002<\/p>\n<h3>\u6b63\u786e\u4f7f\u7528 volatile \u53d8\u91cf\u7684\u6761\u4ef6<\/h3>\n<p>\u6211\u4eec\u53ea\u80fd\u5728\u6709\u9650\u7684\u4e00\u4e9b\u60c5\u5f62\u4e0b\u4f7f\u7528<code>volatile<\/code>\u53d8\u91cf\u66ff\u4ee3\u9501\u3002\u8981\u4f7f<code>volatile<\/code>\u53d8\u91cf\u63d0\u4f9b\u7406\u60f3\u7684\u7ebf\u7a0b\u5b89\u5168\uff0c\u5fc5\u987b\u540c\u65f6\u6ee1\u8db3\u4e0b\u9762\u4e24\u4e2a\u6761\u4ef6\uff1a<\/p>\n<ul>\n<li>\u5bf9\u53d8\u91cf\u7684\u5199\u64cd\u4f5c\u4e0d\u4f9d\u8d56\u4e8e\u5f53\u524d\u503c<\/li>\n<li>\u8be5\u53d8\u91cf\u6ca1\u6709\u5305\u542b\u5728\u5177\u6709\u5176\u4ed6\u53d8\u91cf\u7684\u4e0d\u53d8\u5f0f\u4e2d<\/li>\n<\/ul>\n<p>\u5b9e\u9645\u4e0a\uff0c\u8fd9\u4e9b\u6761\u4ef6\u8868\u660e\uff0c\u53ef\u4ee5\u88ab\u5199\u5165<code>volatile<\/code>\u53d8\u91cf\u7684\u8fd9\u4e9b\u6709\u6548\u503c\u72ec\u7acb\u4e8e\u4efb\u4f55\u7a0b\u5e8f\u7684\u72b6\u6001\uff0c\u5305\u62ec\u53d8\u91cf\u7684\u5f53\u524d\u72b6\u6001\u3002<\/p>\n<p>\u7b2c\u4e00\u4e2a\u6761\u4ef6\u7684\u9650\u5236\u4f7f<code>volatile<\/code>\u53d8\u91cf\u4e0d\u80fd\u7528\u4f5c\u7ebf\u7a0b\u5b89\u5168\u8ba1\u6570\u5668\u3002\u867d\u7136\u589e\u91cf\u64cd\u4f5c<code>x++<\/code>\u770b\u4e0a\u53bb\u7c7b\u4f3c\u4e00\u4e2a\u5355\u72ec\u64cd\u4f5c\uff0c\u5b9e\u9645\u4e0a\u5b83\u662f\u4e00\u4e2a\u7531\u8bfb\u53d6\uff0d\u4fee\u6539\uff0d\u5199\u5165\u64cd\u4f5c\u5e8f\u5217\u7ec4\u6210\u7684\u7ec4\u5408\u64cd\u4f5c\uff0c\u5fc5\u987b\u4ee5\u539f\u5b50\u65b9\u5f0f\u6267\u884c\uff0c\u800c<code>volatile<\/code>\u4e0d\u80fd\u63d0\u4f9b\u5fc5\u987b\u7684\u539f\u5b50\u7279\u6027\u3002\u5b9e\u73b0\u6b63\u786e\u7684\u64cd\u4f5c\u9700\u8981\u4f7f x \u7684\u503c\u5728\u64cd\u4f5c\u671f\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u800c<code>volatile<\/code>\u53d8\u91cf\u65e0\u6cd5\u5b9e\u73b0\u8fd9\u70b9\uff08\u7136\u800c\uff0c\u5982\u679c\u5c06\u503c\u8c03\u6574\u4e3a\u53ea\u4ece\u5355\u4e2a\u7ebf\u7a0b\u5199\u5165\uff0c\u90a3\u4e48\u53ef\u4ee5\u5ffd\u7565\u7b2c\u4e00\u4e2a\u6761\u4ef6\uff09<\/p>\n<p>\u5927\u591a\u6570\u7f16\u7a0b\u60c5\u5f62\u90fd\u4f1a\u4e0e\u8fd9\u4e24\u4e2a\u6761\u4ef6\u7684\u5176\u4e2d\u4e4b\u4e00\u51b2\u7a81\uff0c\u4f7f\u5f97<code>volatile<\/code>\u53d8\u91cf\u4e0d\u80fd\u50cf<code>synchronized<\/code>\u90a3\u6837\u666e\u904d\u9002\u7528\u4e8e\u5b9e\u73b0\u7ebf\u7a0b\u5b89\u5168\u3002\u6e05\u53551 \u663e\u793a\u4e86\u4e00\u4e2a\u975e\u7ebf\u7a0b\u5b89\u5168\u7684\u6570\u503c\u8303\u56f4\u7c7b\u3002\u5b83\u5305\u542b\u4e86\u4e00\u4e2a\u4e0d\u53d8\u5f0f \u2014\u2014 \u4e0b\u754c\u603b\u662f\u5c0f\u4e8e\u6216\u7b49\u4e8e\u4e0a\u754c\u3002<\/p>\n<p>\u6e05\u53551. \u975e\u7ebf\u7a0b\u5b89\u5168\u7684\u6570\u503c\u8303\u56f4\u7c7b<\/p>\n<pre><code class=\"language-java\">@NotThreadSafe\npublic class NumberRange {\n    private int lower, upper;\n\n    public int getLower() { return lower; }\n    public int getUpper() { return upper; }\n\n    public void setLower(int value) {\n        if (value &gt; upper)\n            throw new IllegalArgumentException(...);\n        lower = value;\n    }\n\n    public void setUpper(int value) {\n        if (value &lt; lower)\n            throw new IllegalArgumentException(...);\n        upper = value;\n    }\n}<\/code><\/pre>\n<p>\u8fd9\u79cd\u65b9\u5f0f\u9650\u5236\u4e86\u8303\u56f4\u7684\u72b6\u6001\u53d8\u91cf\uff0c\u56e0\u6b64\u5c06 lower \u548c upper \u5b57\u6bb5\u5b9a\u4e49\u4e3a<code>volatile<\/code>\u7c7b\u578b\u4e0d\u80fd\u591f\u5145\u5206\u5b9e\u73b0\u7c7b\u7684\u7ebf\u7a0b\u5b89\u5168\uff1b\u4ece\u800c\u4ecd\u7136\u9700\u8981\u4f7f\u7528\u540c\u6b65\u3002\u5426\u5219\uff0c\u5982\u679c\u51d1\u5de7\u4e24\u4e2a\u7ebf\u7a0b\u5728\u540c\u4e00\u65f6\u95f4\u4f7f\u7528\u4e0d\u4e00\u81f4\u7684\u503c\u6267\u884c<code>setLower<\/code>\u548c<code>setUpper<\/code>\u7684\u8bdd\uff0c\u5219\u4f1a\u4f7f\u8303\u56f4\u5904\u4e8e\u4e0d\u4e00\u81f4\u7684\u72b6\u6001\u3002\u4f8b\u5982\uff0c\u5982\u679c\u521d\u59cb\u72b6\u6001\u662f<code>(0, 5)<\/code>\uff0c\u540c\u4e00\u65f6\u95f4\u5185\uff0c\u7ebf\u7a0b A \u8c03\u7528<code>setLower(4)<\/code>\u5e76\u4e14\u7ebf\u7a0b B \u8c03\u7528<code>setUpper(3)<\/code>\uff0c\u663e\u7136\u8fd9\u4e24\u4e2a\u64cd\u4f5c\u4ea4\u53c9\u5b58\u5165\u7684\u503c\u662f\u4e0d\u7b26\u5408\u6761\u4ef6\u7684\uff0c\u90a3\u4e48\u4e24\u4e2a\u7ebf\u7a0b\u90fd\u4f1a\u901a\u8fc7\u7528\u4e8e\u4fdd\u62a4\u4e0d\u53d8\u5f0f\u7684\u68c0\u67e5\uff0c\u4f7f\u5f97\u6700\u540e\u7684\u8303\u56f4\u503c\u662f<code>(4, 3)<\/code> \u2014\u2014 \u4e00\u4e2a\u65e0\u6548\u503c\u3002\u81f3\u4e8e\u9488\u5bf9\u8303\u56f4\u7684\u5176\u4ed6\u64cd\u4f5c\uff0c\u6211\u4eec\u9700\u8981\u4f7f<code>setLower()<\/code>\u548c<code>setUpper()<\/code>\u64cd\u4f5c\u539f\u5b50\u5316 \u2014\u2014 \u800c\u5c06\u5b57\u6bb5\u5b9a\u4e49\u4e3a<code>volatile<\/code>\u7c7b\u578b\u662f\u65e0\u6cd5\u5b9e\u73b0\u8fd9\u4e00\u76ee\u7684\u7684\u3002<\/p>\n<h3>\u6027\u80fd\u8003\u8651<\/h3>\n<p>\u4f7f\u7528<code>volatile<\/code>\u53d8\u91cf\u7684\u4e3b\u8981\u539f\u56e0\u662f\u5176\u7b80\u6613\u6027\uff1a\u5728\u67d0\u4e9b\u60c5\u5f62\u4e0b\uff0c\u4f7f\u7528<code>volatile<\/code>\u53d8\u91cf\u8981\u6bd4\u4f7f\u7528\u76f8\u5e94\u7684\u9501\u7b80\u5355\u5f97\u591a\u3002\u4f7f\u7528<code>volatile<\/code>\u53d8\u91cf\u6b21\u8981\u539f\u56e0\u662f\u5176\u6027\u80fd\uff1a\u67d0\u4e9b\u60c5\u51b5\u4e0b\uff0c<code>volatile<\/code>\u53d8\u91cf\u540c\u6b65\u673a\u5236\u7684\u6027\u80fd\u8981\u4f18\u4e8e\u9501\u3002<\/p>\n<p>\u5728\u76ee\u524d\u5927\u591a\u6570\u7684\u5904\u7406\u5668\u67b6\u6784\u4e0a\uff0c<code>volatile<\/code>\u8bfb\u64cd\u4f5c\u5f00\u9500\u975e\u5e38\u4f4e\uff0c\u51e0\u4e4e\u548c\u975e<code>volatile<\/code>\u8bfb\u64cd\u4f5c\u4e00\u6837\u3002\u800c<code>volatile<\/code>\u5199\u64cd\u4f5c\u7684\u5f00\u9500\u8981\u6bd4\u975e<code>volatile<\/code>\u5199\u64cd\u4f5c\u591a\u5f88\u591a\uff0c\u56e0\u4e3a\u8981\u4fdd\u8bc1\u53ef\u89c1\u6027\u9700\u8981\u5b9e\u73b0\u5185\u5b58\u754c\u5b9a\uff08<code>Memory Fence<\/code>\uff09\uff0c\u5373\u4fbf\u5982\u6b64\uff0c<code>volatile<\/code>\u7684\u603b\u5f00\u9500\u4ecd\u7136\u8981\u6bd4\u9501\u83b7\u53d6\u4f4e\u3002<\/p>\n<p><code>volatile<\/code>\u64cd\u4f5c\u4e0d\u4f1a\u50cf\u9501\u4e00\u6837\u9020\u6210\u963b\u585e\uff0c\u56e0\u6b64\uff0c\u5728\u80fd\u591f\u5b89\u5168\u4f7f\u7528<code>volatile<\/code>\u7684\u60c5\u51b5\u4e0b\uff0c<code>volatile<\/code>\u53ef\u4ee5\u63d0\u4f9b\u4e00\u4e9b\u4f18\u4e8e\u9501\u7684\u53ef\u4f38\u7f29\u7279\u6027\u3002\u5982\u679c\u8bfb\u64cd\u4f5c\u7684\u6b21\u6570\u8981\u8fdc\u8fdc\u8d85\u8fc7\u5199\u64cd\u4f5c\uff0c\u4e0e\u9501\u76f8\u6bd4\uff0c<code>volatile<\/code>\u53d8\u91cf\u901a\u5e38\u80fd\u591f\u51cf\u5c11\u540c\u6b65\u7684\u6027\u80fd\u5f00\u9500\u3002<\/p>\n<h2>\u7ed3\u8bba<\/h2>\n<p>\u4e0e\u9501\u76f8\u6bd4\uff0c<code>volatile<\/code>\u53d8\u91cf\u662f\u4e00\u79cd\u975e\u5e38\u7b80\u5355\u4f46\u540c\u65f6\u53c8\u975e\u5e38\u8106\u5f31\u7684\u540c\u6b65\u673a\u5236\uff0c\u5b83\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\u5c06\u63d0\u4f9b\u4f18\u4e8e\u9501\u7684\u6027\u80fd\u548c\u4f38\u7f29\u6027\u3002\u5982\u679c\u4e25\u683c\u9075\u5faa<code>volatile<\/code>\u7684\u4f7f\u7528\u6761\u4ef6\uff1a\u5373\u53d8\u91cf\u771f\u6b63\u72ec\u7acb\u4e8e\u5176\u4ed6\u53d8\u91cf\u548c\u81ea\u5df1\u4ee5\u524d\u7684\u503c\uff0c\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\u53ef\u4ee5\u4f7f\u7528<code>volatile<\/code>\u4ee3\u66ff<code>synchronized<\/code>\u6765\u7b80\u5316\u4ee3\u7801\u3002\u7136\u800c\uff0c\u4f7f\u7528<code>volatile<\/code>\u7684\u4ee3\u7801\u5f80\u5f80\u6bd4\u4f7f\u7528\u9501\u7684\u4ee3\u7801\u66f4\u52a0\u5bb9\u6613\u51fa\u9519\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u7981\u6b62\u7f16\u8bd1\u5668\u91cd\u6392 \u7981\u7528\u5bc4\u5b58\u5668\uff0c\u80fd\u591f\u5373\u4f7f\u5237\u65b0\u5185\u5b58\u6570\u636e\u66f4\u65b0 Java\u8bed\u8a00\u4e2d\u7684volatile\u53d8\u91cf\u53ef\u4ee5\u88ab\u770b\u4f5c\u662f\u4e00\u79cd\u7a0b\u5ea6 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[43],"tags":[50],"class_list":["post-80","post","type-post","status-publish","format-standard","hentry","category-java-basic","tag-volatile"],"_links":{"self":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/80","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/comments?post=80"}],"version-history":[{"count":0,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/80\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/media?parent=80"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/categories?post=80"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/tags?post=80"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}