问如何在java中启动ThreadGroup？

EN

public class ThreadGroupExample
{
    public static void main(String[] args)
    {
    ThreadGroup thGroup1 = new ThreadGroup("ThreadGroup1");

    /* createting threads and adding into thread grout "thGroup1" */
    Thread1 th1 = new Thread1(thGroup1, "JAVA");
    Thread1 th2 = new Thread1(thGroup1, "JDBC");
    Thread2 th3 = new Thread2(thGroup1, "EJB");
    Thread2 th4 = new Thread2(thGroup1, "XML");

    /* starting all thread one by one */
    th1.start();
    th2.start();
    th3.start();
    th4.start();

    // thGroup1.start();

    thGroup1.stop();

    }
}

class Thread1 extends Thread
{
    Thread1(ThreadGroup tg, String name)
    {
    super(tg, name);
    }

    @Override
    public void run()
    {
    for (int i = 0; i < 10; i++)
    {
        ThreadGroup tg = getThreadGroup();
        System.out.println(getName() + "\t" + i + "\t" + getPriority()
            + "\t" + tg.getName());
    }
    }
}

class Thread2 extends Thread
{

    Thread2(String name)
    {
    super(name);
    }

    Thread2(ThreadGroup tg, String name)
    {
    super(tg, name);
    }

    @Override
    public void run()
    {
    for (int i = 0; i < 10; i++)
    {
        ThreadGroup tg = getThreadGroup();
        System.out.println(getName() + "\t" + i + "\t" + getPriority()
            + "\t" + tg.getName());
    }
    }
}