深入理解JUC：第六章：Semaphore信号灯

理论：

Semaphore 是 synchronized 的加强版，作用是控制线程的并发数量

多个线程抢多个资源，下面案例是有六台车抢三个停车位

使用Semaphore的代码：

    public class Demo {
     
        public static void main(String[] args) throws Exception{
            //模拟三个停车位
            Semaphore semaphore = new Semaphore(3);
            //模拟六台车
            for (int i = 1; i <= 6; i++) {
                new Thread(()->{
                    try {
                        semaphore.acquire();//减一
                        //semaphore.release();//加一
                        //semaphore.release(2);//加二
                        System.out.println(Thread.currentThread().getName()+"\t 抢到车位");
                        Thread.sleep(2000);
                        System.out.println(Thread.currentThread().getName()+"\t 停车2秒后离开车位");
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }finally {
                        semaphore.release();
                    }
                },String.valueOf(i)).start();
            }
        }
    }

控制台：