Java笔记-Semaphore简单应用实例

短命女 2022-09-12 05:42 51阅读 0赞

这个Semaphore和QSemaphore使用和原理一模一样。

这里简单写了个例子，开了10个线程去拿邻界资源，资源只有一个，拿到后要进行5s的业务错了，使用Semaphore，如果此资源被占用，那么该线程将会被挂起。

程序运行截图如下：

D:\java8\content\bin\java.exe -javaagent:D:\idea\content\lib\idea_rt.jar=52182:D:\idea\content\bin -Dfile.encoding=UTF-8 -classpath D:\java8\content\jre\lib\charsets.jar;D:\java8\content\jre\lib\deploy.jar;D:\java8\content\jre\lib\ext\access-bridge-64.jar;D:\java8\content\jre\lib\ext\cldrdata.jar;D:\java8\content\jre\lib\ext\dnsns.jar;D:\java8\content\jre\lib\ext\jaccess.jar;D:\java8\content\jre\lib\ext\jfxrt.jar;D:\java8\content\jre\lib\ext\localedata.jar;D:\java8\content\jre\lib\ext\nashorn.jar;D:\java8\content\jre\lib\ext\sunec.jar;D:\java8\content\jre\lib\ext\sunjce_provider.jar;D:\java8\content\jre\lib\ext\sunmscapi.jar;D:\java8\content\jre\lib\ext\sunpkcs11.jar;D:\java8\content\jre\lib\ext\zipfs.jar;D:\java8\content\jre\lib\javaws.jar;D:\java8\content\jre\lib\jce.jar;D:\java8\content\jre\lib\jfr.jar;D:\java8\content\jre\lib\jfxswt.jar;D:\java8\content\jre\lib\jsse.jar;D:\java8\content\jre\lib\management-agent.jar;D:\java8\content\jre\lib\plugin.jar;D:\java8\content\jre\lib\resources.jar;D:\java8\content\jre\lib\rt.jar;D:\IDEAProject\SemaphoreJavaDemo\target\classes cn.it1995.MyMain
    2021-08-10 16:12:46->Thread[pool-1-thread-1,5,main] 开始处理业务
    2021-08-10 16:12:51->Thread[pool-1-thread-1,5,main] 处理业务完成
    2021-08-10 16:12:51->Thread[pool-1-thread-3,5,main] 开始处理业务
    2021-08-10 16:12:56->Thread[pool-1-thread-3,5,main] 处理业务完成
    2021-08-10 16:12:56->Thread[pool-1-thread-7,5,main] 开始处理业务
    2021-08-10 16:13:01->Thread[pool-1-thread-7,5,main] 处理业务完成
    2021-08-10 16:13:01->Thread[pool-1-thread-2,5,main] 开始处理业务
    2021-08-10 16:13:06->Thread[pool-1-thread-2,5,main] 处理业务完成
    2021-08-10 16:13:06->Thread[pool-1-thread-5,5,main] 开始处理业务
    2021-08-10 16:13:11->Thread[pool-1-thread-5,5,main] 处理业务完成
    2021-08-10 16:13:11->Thread[pool-1-thread-8,5,main] 开始处理业务
    2021-08-10 16:13:16->Thread[pool-1-thread-8,5,main] 处理业务完成
    2021-08-10 16:13:16->Thread[pool-1-thread-4,5,main] 开始处理业务
    2021-08-10 16:13:21->Thread[pool-1-thread-4,5,main] 处理业务完成
    2021-08-10 16:13:21->Thread[pool-1-thread-6,5,main] 开始处理业务
    2021-08-10 16:13:26->Thread[pool-1-thread-6,5,main] 处理业务完成
    2021-08-10 16:13:26->Thread[pool-1-thread-10,5,main] 开始处理业务
    2021-08-10 16:13:31->Thread[pool-1-thread-10,5,main] 处理业务完成
    2021-08-10 16:13:31->Thread[pool-1-thread-9,5,main] 开始处理业务
    
    Process finished with exit code -1

程序结构如下：

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVQxOTk1_size_11_color_FFFFFF_t_70_g_se_x_16][]

源码如下：

MyMain.java

package cn.it1995;
    
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    
    public class MyMain {
    
        public static void main(String[] args) {
    
            ExecutorService threadPool = Executors.newCachedThreadPool();
            for(int i = 0; i < 10; i++){
    
                threadPool.execute(new MyThread());
            }
        }
    }

MyResource.java

package cn.it1995;
    
    import java.text.SimpleDateFormat;
    import java.util.Date;
    import java.util.concurrent.Semaphore;
    
    public class MyResource {
    
        private static Semaphore semaphore = new Semaphore(1);
        private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//设置日期格式
    
        public static void todoSth(){
    
            try {
    
                semaphore.acquire(1);
    
                Date startDate = new Date();
                String time = sdf.format(startDate);
    
                System.out.println(time + "->" + Thread.currentThread() + " 开始处理业务");
                Thread.sleep(5 * 1000);
    
                Date endDate = new Date();
                time = sdf.format(endDate);
                System.out.println(time + "->" + Thread.currentThread() + " 处理业务完成");
            }
            catch (Exception e){
    
                e.printStackTrace();
            }
            finally {
    
                semaphore.release(1);
            }
        }
    }

MyThread.java

package cn.it1995;
    
    public class MyThread implements Runnable {
    
    
        public void run() {
    
            while (true) {
    
                try {
    
                    MyResource.todoSth();
                    Thread.sleep( 1 * 1000);
                }
                catch (InterruptedException e) {
    
                    e.printStackTrace();
                }
            }
        }
    }

源码打包下载地址：

[Java/SemaphoreJavaDemo at master · fengfanchen/Java · GitHub][Java_SemaphoreJavaDemo at master _ fengfanchen_Java _ GitHub]

[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVQxOTk1_size_11_color_FFFFFF_t_70_g_se_x_16]: /images/20220828/45653eac868142fc929352cfd73f5531.png
[Java_SemaphoreJavaDemo at master _ fengfanchen_Java _ GitHub]: https://github.com/fengfanchen/Java/tree/master/SemaphoreJavaDemo