Java多线程应用循环输出ABC方式

public class Test { 
    public static void main(String[] args) { 
        MajusculeABC maj = new MajusculeABC(); 
        Thread t_a = new Thread(new Thread_ABC(maj , 'A')); 
        Thread t_b = new Thread(new Thread_ABC(maj , 'B')); 
        Thread t_c = new Thread(new Thread_ABC(maj , 'C')); 
        t_a.start(); 
        t_b.start(); 
        t_c.start(); 
    } 
} 
class MajusculeABC { 
请补充代码
} 
class Thread_ABC implements Runnable {
请补充代码
}

public class ThreadTest {
    public static void main(String[] args) throws InterruptedException {
        MajusculeABC maj = new MajusculeABC();
        Thread t_a = new Thread(new Thread_ABC(maj , 'A'));
        Thread t_b = new Thread(new Thread_ABC(maj , 'B'));
        Thread t_c = new Thread(new Thread_ABC(maj , 'C'));
        t_a.start();
        t_b.start();
        t_c.start();
    }
    private static class MajusculeABC {
        //        请补充代码
        public MajusculeABC() {
        }

        private int a = 1;

        private synchronized void print(int index, char s) throws InterruptedException {
            do {
                if (s == 'A' && a == 1) {
                    a++;
                    System.out.println(index+"---" + s);
                    notifyAll();
                    break;
                } else if (s == 'B' && a == 2) {
                    a++;
                    System.out.println(index+"---" + s);
                    notifyAll();
                    break;
                } else if (s == 'C' && a == 3) {
                    a = 1;
                    System.out.println(index+"---" + s);
                    notifyAll();
                    break;
                } else {
                    wait();
                }

            } while (true);

        }
    }

    private static class Thread_ABC implements Runnable {

        private char s;
        private MajusculeABC majusculeABC;

        //        请补充代码
        public Thread_ABC(MajusculeABC majusculeABC, char s) {
            this.majusculeABC = majusculeABC;
            this.s = s;
        }

        @Override
        public void run() {
            for (int i = 0; i < 10; i++) {
                try {
                    majusculeABC.print(i, s);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

}