Android 2.2 Phone - Dynamically Loading External Library At Runtime?

I am using and android 2.2 phone for testing and getting an error.

07-27 01:24:55.692: W/System.err(14319): java.lang.ClassNotFoundException: com.shoaib.AndroidCCL.MyClass in loader dalvik.system.DexClassLoader@43abbc20

First I wrote the following class:

Code:
package org.shoaib.androidccl;
import android.util.Log;
public class MyClass {
public MyClass() {
Log.d(MyClass.class.getName(), "MyClass: constructor called.");
}
public void doSomething() {
Log.d(MyClass.class.getName(), "MyClass: doSomething() called.");
}
}

And I packaged it in a DEX file that I saved on my device's SD card as `/sdcard/testdex.jar`.

Then I wrote the program below, after having removed `MyClass` from my Eclipse project and cleaned it:

Code:

public class Main extends Activity {
[MENTION=1299008]supp[/MENTION]ressWarnings("unchecked")
[MENTION=439709]override[/MENTION]
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

[code]....