why do I get this runtime error

 "Aryeh M. Friedman" <Aryeh.Friedman@gmail.com>
Fri, 05 Oct 2007 10:05:53 -0000
When I run this:

package scratch;

import java.io.*;

public class Main extends ClassLoader
        public Main()

        public static void main(String[] args)
                throws Throwable
                Main m=new Main();

                File f=null;

                f = new File("/usr/home/plos/obj/scratch/Main.class");
                int size = (int)f.length();
                byte buff[] = new byte[size];
                FileInputStream fis = new FileInputStream(f);
                DataInputStream dis = new DataInputStream(fis);

                Class klass=m.defineClass("scratch.Main",buff,

                Main m2=(Main) klass.newInstance();

I get:
Exception in thread "main" java.lang.ClassCastException: scratch.Main
cannot be cast to scratch.Main
          at scratch.Main.main(Main.java:29)


This is distilled from attempting to write a class loader and every
attempt ends with the same error (even cutting and pasting web and
junit examples of class loaders and calling them instead of mine).

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