如何保证线程按顺序执行

/*
 有三个线程T1 T2 T3，如何保证他们按顺序执行-转载
在T2的run中，调用t1.join，让t1执行完成后再让T2执行
在T2的run中，调用t2.join，让t2执行完成后再让T3执行
*/
public class ThreadByOrder {

    static Thread t1 = new Thread(new Runnable() {

        @Override
        public void run() {
            System.out.println("t1");
        }
    });

    static Thread t2 = new Thread(new Runnable() {

        @Override
        public void run() {
            try {
                t1.join();
                Thread.sleep(500);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            System.out.println("t2");
        }
    });

    static Thread t3 = new Thread(new Runnable() {

        @Override
        public void run() {
            try {
                t2.join();
                Thread.sleep(500);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            System.out.println("t3");
        }
    });
    public static void main(String[] args) {
        t1.start();
        t2.start();
        t3.start();

    }

}