线程t1,t2,t3 分别输出A,B,C 要求循环输出ABC 10次

public class DemoTest{
    private static String[] flag = {"A"};

    static class AThread extends Thread{
        @Override
        public void run(){
            int i=0;
            while (i<10){
                synchronized (flag){
                    if(flag[0].equals("A")){
                        System.out.print("A");
                        flag[0]="B";
                        i++;
                    }
                    flag.notify();
                    try {
                        flag.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

    static class BThread extends Thread{
        @Override
        public void run(){
            int i=0;
            while (i<10){
                synchronized (flag){
                    if(flag[0].equals("B")){
                        System.out.print("B");
                        flag[0]="C";

                        i++;
                    }
                    flag.notify();

                    try {
                        flag.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

    static class CThread extends Thread{
        @Override
        public void run(){
            int i=0;
            while (i<10){
                synchronized (flag){
                    if(flag[0].equals("C")){
                        System.out.println("C");
                        flag[0]="A";

                        i++;
                    }
                    flag.notify();

                    try {
                        flag.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

    public static void main(String[] args) {
        AThread t1 = new AThread();
        BThread t2 = new BThread();
        CThread t3 = new CThread();
        t1.start();
        t2.start();
        t3.start();
    }
}