java 多线程 day14 Semaphore 线程信号灯

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

/**
 * Created by chengtao on 17/12/5.
 */
public class Thread1401_Semaphore {
    public static void main(String[] args) {
        ExecutorService service = Executors.newCachedThreadPool();
        final  Semaphore sp = new Semaphore(3); //单个信号灯 即实现线程互斥
        for(int i=0;i<10;i++){
            Runnable runnable = new Runnable(){
                public void run(){
                    try {
                        sp.acquire();
                    } catch (InterruptedException e1) {
                        e1.printStackTrace();
                    }
                    System.out.println("线程" + Thread.currentThread().getName() +
                            "进入，当前已有" + (3-sp.availablePermits()) + "个并发");
                    try {
                        Thread.sleep((long)(Math.random()*10000));
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("线程" + Thread.currentThread().getName() +
                            "即将离开");
                    sp.release();
                    //下面代码有时候执行不准确，因为其没有和上面的代码合成原子单元
                    System.out.println("线程" + Thread.currentThread().getName() +
                            "已离开，当前已有" + (3-sp.availablePermits()) + "个并发");
                }
            };
            service.execute(runnable);
        }
    }

}