三个线程，ABC 10次（volatile+synchronized（2 synchronized可以保证内存可见性，所以去掉status 的volatile修饰符）

package ThreadABC;

public class MyThread extends Thread {
    public static  int status = 0;
    @Override
    public void run() {
        while (true) {
            synchronized (MyThread.class) {
                if ("A".equals(Thread.currentThread().getName()) && status < 30 && status % 3 == 0) {
                    System.out.print("A");
                    status++;
                } else if ("B".equals(Thread.currentThread().getName()) && status < 30 && status % 3 == 1) {
                    System.out.print("B");
                    status++;

                } else if ("C".equals(Thread.currentThread().getName()) && status < 30 && status % 3 == 2) {
                    System.out.println("C");
                    status++;
                }
                if (status == 30) {
                    break;
                }
            }
        }
    }

    public MyThread(String name) {
        super(name);
    }
}