线程 继承和实现 区别

// MyRun实现Runnable接口，然后创建一个实例，将这个实例作为多个Thread的参数构造Thread类，然后启动线程，
//发现这几个线程共享了 MyRun#ato 变量
// 然而上面这个实现接口改成继承Thread，其他都不变，也没啥两样
public class ShareTest {
    private static class MyRun implements Runnable {
        private volatile AtomicInteger ato = new AtomicInteger(5);
        @Override
        public void run() {
            while (true) {
                int tmp = ato.decrementAndGet();
                System.out.println(Thread.currentThread() + " : " + tmp);
                if (tmp <= 0) {
                    break;
                }
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        MyRun run = new MyRun();
        Thread thread1 = new Thread(run, "线程1");
        Thread thread2 = new Thread(run, "线程2");
        thread1.start();
        thread2.start();
        thread1.join();
        thread2.join();
        System.out.println("over");
    }
}
// 上面除了说明使用Runnable更利于资源共享神马的，其实并没有之外，还有一个比较有意思的，为什么会输出-1？
//如果我这个任务是售票的话，妥妥的就超卖了，这个问题留待后续详解
public class ShareTest {
    private static class MyRun extends Thread {
        private volatile AtomicInteger ato = new AtomicInteger(5);
        @Override
        public void run() {
            while (true) {
                int tmp = ato.decrementAndGet();
                System.out.println(Thread.currentThread() + " : " + tmp);
                if (tmp <= 0) {
                    break;
                }
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        MyRun run = new MyRun();
        Thread thread1 = new Thread(run, "线程1");
        Thread thread2 = new Thread(run, "线程2");
        thread1.start();
        thread2.start();
        thread1.join();
        thread2.join();
        System.out.println("over");
    }
}