多线程买票问题:synchronized锁的应用

客官°小女子只卖身不卖艺 2024-04-06 12:49 61阅读 0赞

一个简单的买票问题

public class TestSync {
        public static void main(String[] args) throws InterruptedException {
            MaiPiao piao = new MaiPiao();
            Thread [] threads = new Thread[10];
            for (int i = 0; i < threads.length; i++) {
                threads[i] = new Thread(new Window(piao));
            }
            for (int i = 0; i < threads.length; i++) {
                threads[i].start();
            }
            Thread.sleep(5000);
            piao.tikectCheck();
        }
    }
    class Window implements Runnable{
        private MaiPiao piao;
        public Window(MaiPiao piao) {
            this.piao = piao;
        }
        @Override
        public void run() {
            for (int i = 0; i < 100; i++) {
                piao.sold();
            }
        }
    }
    class MaiPiao{
        private  int tikect=1000;
        public  void sold(){
            tikect--;
        }
        public void tikectCheck(){
            System.out.println(tikect);
        }
    
    }

执行结果：存在多线程抢占一个资源的问题

![83545999eee04b0f90bb9765eb564d7b.png][]

29行加个synchronized，锁住了他，所以一个每个线程要执行后才会执行其他线程。

public class TestSync {
        public static void main(String[] args) throws InterruptedException {
            MaiPiao piao = new MaiPiao();
            Thread [] threads = new Thread[10];
            for (int i = 0; i < threads.length; i++) {
                threads[i] = new Thread(new Window(piao));
            }
            for (int i = 0; i < threads.length; i++) {
                threads[i].start();
            }
            Thread.sleep(5000);
            piao.tikectCheck();
        }
    }
    class Window implements Runnable{
        private MaiPiao piao;
        public Window(MaiPiao piao) {
            this.piao = piao;
        }
        @Override
        public void run() {
            for (int i = 0; i < 100; i++) {
                piao.sold();
            }
        }
    }
    class MaiPiao{
        private  int tikect=1000;
        public synchronized void sold(){
            tikect--;
        }
        public void tikectCheck(){
            System.out.println(tikect);
        }
    
    }

执行结果![282cc1b390534b7db6d5898398108b3f.png][]

synchronized实现同步的基础：Java中的每一个对象都可以作为锁。具体表现为以下3种形式

·对于普通同步方法，锁是当前实例对象。

·对于静态同步方法，锁是当前类的Class对象。

![3444a23885ec455f9d0b5db7bdaf4beb.png][]

·对于同步方法块，锁是Synchonized括号里配置的对象

![ebad40390cc842f5a01787b9d8fc0f92.png][]

类锁只有一个，谁拿到谁执行。退出或抛出异常时必须释放锁

[83545999eee04b0f90bb9765eb564d7b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/b8fd2719a8244803b566bfa783211283.png
[282cc1b390534b7db6d5898398108b3f.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/4f8ab2978e274cc29c9156258195c674.png
[3444a23885ec455f9d0b5db7bdaf4beb.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/33a600fe9a714a83b14ff4e0053cebff.png
[ebad40390cc842f5a01787b9d8fc0f92.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/ba0e9caf49cc4e02b7d821fb0d3cfca6.png