現在有T1、T2、T3三個線程，你怎樣保證T2在T1執行完後執行，T3在T2執行完後執行

現在有T1、T2、T3三個線程，你怎樣保證T2在T1執行完後執行，T3在T2執行完後執行

public static void main(String[] args) {
    Thread t1 = new Thread(new Runnable() {
        @Override
        public void run() {
            System.out.println("線程A");
        }
    });
    Thread t2 = new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                t1.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }  System.out.println("線程B");
    });
    Thread t3 = new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                t2.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("線程C");
        }
    });
    t1.start();
    t2.start();
    t3.start();
}