Failing to load class definition from jar

I ran across an issue when attempting to port an application over to JApplet so it can run on a browser.

Program Contents:

Jar file. Contains my CustomClassLoader implementation. Stored on website.
Content directory. Filled with compiled classes. Stored on the users computer.

Issue:

I am getting a NoClassDefFoundError when attempting to load .class files in the content directory with my CustomClassLoader.

The error, although unattainable, relates back to a class inside the jar. The class is abstract. All the .class files in the content directory extend this class and fill all the required methods. Upon loading these classes, the error is thrown. The program, when ran normally java -jar file.jar, works perfectly fine.

This makes me believe it has to do with the classpath.

Security Setup:

I am running the applet through the appletviewer command like so:

 appletviewer -J-Djava.security.policy=policy file.html

In the same directory is my policy file:

grant {
  permission java.lang.RuntimePermission "getenv.APPDATA";
  permission java.io.FilePermission "<<ALL FILES>>", "read, write, delete, execute";
  permission java.lang.RuntimePermission "exitVM";
  permission java.util.PropertyPermission "user.name", "read";
  permission java.lang.RuntimePermission "createClassLoader";
};

As far as I know, no other security exceptions are being thrown. The applet is signed.

HTML File Used To Load Applet:

<!DOCTYPE html>
<html>
    <body>
        <object width="1000" height="600" classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
            codebase="http://java.sun.com/products/plugin/autodl/jinstall-1_4-windows-i586.cab#Version=1,4,0,0">
            <param name="archive" value="file.jar"/>
            <param name="code" value="package.to.Boot"/>
        </object>
    </body>
</html>

Any help towards fixing this problem is greatly appreciated.

CustomClassLoader.java:

package org.obicere.cc.methods;

import java.io.File;

public class CustomClassLoader extends ClassLoader {
    //...
    private Class<?> loadClass(final File file) {
        try {
            final byte[] data = IOUtils.readData(file);
            return super.defineClass(file.getName().substring(0, file.getName().length() - 6), data, 0, data.length);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}

Example Runner: CanReachRunner.java

import java.lang.reflect.Method;
import java.util.Random;

import org.obicere.cc.executor.Result;
import org.obicere.cc.tasks.projects.Runner;

public class CanReachRunner extends Runner {

    @Override
    public Result[] getResults(Class<?> clazz) {
        try {
            final Method method = clazz.getMethod("canReach", int.class, int.class, int.class);
            final Random ran = new Random();
            final Result[] results = new Result[10];
            for (int i = 0; i < 10; i++) {
                final int small = ran.nextInt(5) + 5;
                final int large = ran.nextInt(5);
                final int goal = (small + large * 5) + 5 + ran.nextInt(6);
                results[i] = new Result(method.invoke(clazz.newInstance(), small, large, goal), (goal <= small + large * 5) && goal % 5 <= small, small, large, goal);
            }
            return results;
        } catch (Exception e) {
            return new Result[] {};
        }
    }
}

public class CustomClassLoader extends ClassLoader { private Class<?> findClass(String class) { try { File contentDir = ...; // You have to fill this in with the location of the content dir final byte[] data = IOUtils.readData(new File(contentDir, class + ".class"); return defineClass(class, data, 0, data.length); } catch (Exception e) { e.printStackTrace(); return null; } } }

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