闭锁初尝试

浅浅的花香味﹌ 2022-05-23 04:41 160阅读 0赞

以下为一个简单的闭锁的应用：

package JavaDay6_02;
    
    import java.util.concurrent.CountDownLatch;
    
    /**
     * @author myvina@qq.com
     * @date 18-6-2  上午8:55
     */
    
    //在计时测试中使用闭锁来启动和停止线程
    public class Demo1 {
        public long timeTasks(int nThreads, final Runnable task) throws InterruptedException {
            final CountDownLatch startGate = new CountDownLatch(1);
            final CountDownLatch endGate = new CountDownLatch(nThreads);
    
            for(int i = 0; i < nThreads; i++) {
                Thread t = new Thread() {
                    @Override
                    public void run() {
                        try {
                            //线程开始运行，此处等待闭锁打开
                            startGate.await();
                            try {
                                task.run();
                            } finally {
                                //对endGate的闭锁计数器减一
                                endGate.countDown();
                            }
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                };
                t.start();
            }
            long start = System.nanoTime();
            System.out.println("开始执行...");
            //startGate的计数器减一，所有线程开始执行
            startGate.countDown();
            //等待最后一个线程执行完
            endGate.await();
            System.out.println("结束执行...");
            long end = System.nanoTime();
            return end - start;
        }
    
        public static void main(String[] args) {
            Demo1 demo1= new Demo1();
            Runnable task = new Runnable() {
                @Override
                public void run() {
                    long sum = 0L;
                    for(int i = 0; i < Integer.MAX_VALUE; i++) {
                        sum += i;
                    }
                    System.out.println(sum);
                }
            };
    
            try {
                System.out.println("运行时间为： " + demo1.timeTasks(10, task));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

运行结果为：

![70][]

[70]: /images/20220523/9139364ddc474e5498cc7edc5373cae1.png