class forName 用法

import javax.mail.internet.InternetAddress;
import java.util.Calendar;
import java.util.Enumeration;
import java.net.NetworkInterface;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.text.DateFormat;
import java.io.DataInputStream;

class ChildThread
{
    public String name;
    
    public ChildThread()
    {
        this.name = "hello world";
    }
    
    public void run()
    {
        System.out.println(name);
    }
}

public class Test
{
    public static void main(String args[]) throws Exception
    {

            ChildThread t = (ChildThread) Class.forName("ChildThread").newInstance();
            t.run();
    }
}