{"id":16652,"date":"2024-03-15T13:24:11","date_gmt":"2024-03-15T13:24:11","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-to-use-the-semaphore-tool-in-java-for-multi-threading\/"},"modified":"2025-08-07T04:45:16","modified_gmt":"2025-08-07T04:45:16","slug":"how-to-use-the-semaphore-tool-in-java-for-multi-threading","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-to-use-the-semaphore-tool-in-java-for-multi-threading\/","title":{"rendered":"How to use the Semaphore tool in Java for multi-threadi&#8230;"},"content":{"rendered":"<p>Semaphore is a crucial tool in Java for managing access to shared resources by multiple threads. It acts as a counter semaphore, controlling the number of threads accessing a resource at the same time.<\/p>\n<p>\nHere are some common methods of semaphore:<\/p>\n<ol>\n<li>acquire(): Obtain a permit; if no permit is available, the thread will be blocked until one is available.<\/li>\n<li>release(): Releases a permit, allowing other threads to acquire the permit. If there are blocked threads waiting for the permit, it will select one thread to acquire the permit.<\/li>\n<\/ol>\n<p>Here is an example code using Semaphore:<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">import<\/span> java.util.concurrent.Semaphore;\r\n\r\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title class_\">SemaphoreExample<\/span> {\r\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title function_\">main<\/span><span class=\"hljs-params\">(String[] args)<\/span> {\r\n        <span class=\"hljs-comment\">\/\/ \u521b\u5efaSemaphore\u5bf9\u8c61\uff0c\u6307\u5b9a\u8bb8\u53ef\u7684\u6570\u91cf\u4e3a3<\/span>\r\n        <span class=\"hljs-type\">Semaphore<\/span> <span class=\"hljs-variable\">semaphore<\/span> <span class=\"hljs-operator\">=<\/span> <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">Semaphore<\/span>(<span class=\"hljs-number\">3<\/span>);\r\n\r\n        <span class=\"hljs-comment\">\/\/ \u521b\u5efa10\u4e2a\u7ebf\u7a0b<\/span>\r\n        <span class=\"hljs-keyword\">for<\/span> (<span class=\"hljs-type\">int<\/span> <span class=\"hljs-variable\">i<\/span> <span class=\"hljs-operator\">=<\/span> <span class=\"hljs-number\">0<\/span>; i &lt; <span class=\"hljs-number\">10<\/span>; i++) {\r\n            <span class=\"hljs-keyword\">final<\/span> <span class=\"hljs-type\">int<\/span> <span class=\"hljs-variable\">threadNum<\/span> <span class=\"hljs-operator\">=<\/span> i;\r\n            <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">Thread<\/span>(() -&gt; {\r\n                <span class=\"hljs-keyword\">try<\/span> {\r\n                    <span class=\"hljs-comment\">\/\/ \u83b7\u53d6\u8bb8\u53ef<\/span>\r\n                    semaphore.acquire();\r\n                    System.out.println(<span class=\"hljs-string\">\"Thread \"<\/span> + threadNum + <span class=\"hljs-string\">\" is running\"<\/span>);\r\n                    Thread.sleep(<span class=\"hljs-number\">1000<\/span>);\r\n                    System.out.println(<span class=\"hljs-string\">\"Thread \"<\/span> + threadNum + <span class=\"hljs-string\">\" is finished\"<\/span>);\r\n                } <span class=\"hljs-keyword\">catch<\/span> (InterruptedException e) {\r\n                    e.printStackTrace();\r\n                } <span class=\"hljs-keyword\">finally<\/span> {\r\n                    <span class=\"hljs-comment\">\/\/ \u91ca\u653e\u8bb8\u53ef<\/span>\r\n                    semaphore.release();\r\n                }\r\n            }).start();\r\n        }\r\n    }\r\n}\r\n<\/code><\/pre>\n<p>The code above creates a Semaphore object with 3 permits. It then creates 10 threads, each of which must acquire a permit before executing. If permits are unavailable, the threads will be blocked. After completing their task, they release the permit so that other threads can acquire it to continue executing.<\/p>\n<p>When you run the code above, you will find that only a maximum of 3 threads are executing simultaneously, while the others will be blocked, waiting for the release of permission. This can effectively control access to shared resources.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Semaphore is a crucial tool in Java for managing access to shared resources by multiple threads. It acts as a counter semaphore, controlling the number of threads accessing a resource at the same time. Here are some common methods of semaphore: acquire(): Obtain a permit; if no permit is available, the thread will be blocked [&hellip;]<\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[453,1402,299,1404,1403],"class_list":["post-16652","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-development","tag-guide","tag-programming","tag-technology","tag-tutorial"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>How to use the Semaphore tool in Java for multi-threadi... - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn about how to use the semaphore tool in java for multi-threading?. 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