Android :: Dynamically Loading JAR File At Runtime

I am storing the required test.jar file in the /sdcard. I want to load it dynamically at runtime and want to execute a function xyz() resides in that. For this purpose I had written following code:
But got ClassCastException : dalvik.system.PathClassLoader

Following is my code ,
import java.io.File; import java.io.IOException; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.net.URL; import java.net.URLClassLoader;

import android.app.Activity; import android.os.Bundle; import android.util.Log;
public class Collabera extends Activity {
/** Called when the activity is first created. */
private static final Class[] parameters = new Class[] { URL.class };
public static void loadURLClass(String classPathURL) throws IOException {
File f = new File(classPathURL);
URL url = f.toURL();
URLClassLoader systemLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();
Class systemLoaderClass = URLClassLoader.class;
try { Method method = systemLoaderClass.getDeclaredMethod("addURL", parameters);
method.setAccessible(true);
method.invoke(systemLoader, new Object[] { url });
} catch (Throwable t) { t.printStackTrace();
throw new IOException( "Error, could not add URL to system classloader");
} }
@Override
public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Log.i("See","**************Before Loading Class Path**************");
try { Class.forName("test.Test1");
} catch (ClassNotFoundException e) { System.out.println(" Test Class Not Found ....");
} Log.i("See","**************After Loading Class Path**************");
try { loadURLClass("//sdcard//test.jar");
Class c = Class.forName("test.Test1");
Log.i("See"," Test Class Found ....");
Method method = c.getMethod("xyz", null);
Object o = c.newInstance();
String s = (String) method.invoke(o);
Log.i("See","Got method: " + s);
} catch (ClassNotFoundException e) { System.out.println(" Test Class Not Found ....");
} catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace();
} } }