The code below supposed to load an applet from a URL and define it. The example below uses the Animator class from the /usr/local/java jsut to demonstrate the bug. Everything goes smoothly until defineClass() is called and fails ( tried on Windows as well as with Solaris 1.1.6 and 1.1.7)
java.lang.ClassFormatError: Illegal constant pool type

import java.util.*;
import java.net.*;
import java.io.*;
import java.applet.*;
public class FarmletTender {
    public FarmletTender () {
    }
    static public void main(String args[]) {
        try {
            FarmletLoader loader = new FarmletLoader();
         Applet farmlet =
           (Applet)loader.loadClass("Applet", true).newInstance();
            System.out.println("Hello World");
            Thread.sleep(10000);
        } catch (Exception e) {
            System.out.println("Got exception: " + e);
        }
    }
}
class FarmletLoader extends ClassLoader {
    //String host;
    //int port;
    Hashtable cache = new Hashtable();

FarmletLoader() {
super();
}

    private byte loadClassData(String name)[] throws IOException {
        // load the class data from the connection
        URL url =
       new URL("file:/usr/local/java/jdk1.1.6/solaris/demo/Animator/1.1/Animator.class");
        System.out.println("url is: " + url);
        URLConnection link = url.openConnection();
        System.out.println("length is: " + link.getContentLength());
        System.out.println("type is: " + link.getContentType());
        System.out.println("encoding is " + link.getContentEncoding());
        System.out.println("content object is: " + link.getContent());
        byte data[] = new byte[link.getContentLength()];
        link.getInputStream().read(data, 0, link.getContentLength());
        System.out.println(" content is: " + data[0] + data[1] + data[2]);
        return data;
    }
    public synchronized Class loadClass(String name,
                                        boolean resolve)
      throws ClassNotFoundException {
        try {
            Class c = (Class)cache.get(name);
            if (c == null) {
                byte data[] = loadClassData(name);
                System.out.println("length = " + data.length);
                c = defineClass(name, data, 0, data.length);
                System.out.println("here " + c);
                cache.put(name, c);
                System.out.println("here");
            }
            if (resolve)
                resolveClass(c);
                    System.out.println("here");
            return c;
        } catch (Exception e) {
            throw new ClassNotFoundException("Error loading class " + name
+
                              ": " + e);
        }
    }
}
The output as below:

javac FarmletTender.java
java FarmletTender
url is: file:/usr/local/java/jdk1.1.6/solaris/demo/Animator/1.1/Animator.class
length is: 16323
type is: application/java-vm
encoding is null
content object is: java.io.BufferedInputStream@1dce0f0c
 content is: -54-2-70
length = 16323
java.lang.ClassFormatError: Illegal constant pool type
        at java.lang.ClassLoader.defineClass(ClassLoader.java)
        at FarmletLoader.loadClass(FarmletTender.java:55)
        at FarmletTender.main(FarmletTender.java:15)


4165059 bug is opened against JDK1.2 beta4, please note that the error message is differnet on JDK 1.2 beta4.