AtomicInteger原子类,这种情况下为什么线程不安全?

AtomicInteger是原子类,线程应该是安全的,为什么这种情况下,导致了线程不安全?

class MyThread111 implements Runnable{

    AtomicInteger count = new AtomicInteger(10);

    @Override
    public void run() {
        count.decrementAndGet();
        System.out.println("线程" +Thread.currentThread().getName() + "购票成功,剩余:" + count);
    }

    public static void main(String[] args) {
        MyThread111 myThread1 = new MyThread111();
        Thread thread = new Thread(myThread1);
        Thread thread2 = new Thread(myThread1);
        Thread thread3 = new Thread(myThread1);
        thread.start();
        thread2.start();
        thread3.start();
    }
}

运行结果:

线程Thread-0购票成功,剩余:8
线程Thread-2购票成功,剩余:7
线程Thread-1购票成功,剩余:8

期望值是:

线程Thread-0购票成功,剩余:8
线程Thread-2购票成功,剩余:7
线程Thread-1购票成功,剩余:9

为什么运行的结果是线程不安全的呢? AtomicInteger是线程安全的啊

原子类的方法也都是原子性的,但是不能保证多个方法连续调用是原子性的,这里先自减再打印,结合在一起不能保证线程安全,还是要加锁或者再定义一个变量去接收自减操作后的值,再打印这个变量的值。
比如上述状况,就是 线程0 先走了自减,还没来得及打印,线程1就进行自减操作,这时候线程0打印的时候获取的count就是 8

count.decrementAndGet(); 时的count,跟println时已经不一样了。

public class MyThread111 implements Runnable{

    AtomicInteger count = new AtomicInteger(10);

    @Override
    public void run() {
        int cur_count = count.decrementAndGet();
        System.out.println("线程" +Thread.currentThread().getName() + "购票成功,剩余:" + cur_count);
    }

    public static void main(String[] args) {
        MyThread111 myThread1 = new MyThread111();
        Thread thread = new Thread(myThread1);
        Thread thread2 = new Thread(myThread1);
        Thread thread3 = new Thread(myThread1);
        thread.start();
        thread2.start();
        thread3.start();
    }
}