Android : forName() method ClassNotFoundException

I was trying to test how forName() works, but I'm getting ClassNotFoundException for some reason. Here's my code:

package practicePackage;

import java.lang.Class;

public class mainClass {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        try {
            Class testSar = Class.forName("practicePackage.Animal");
            testSar.eat();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}

Here's the complete view of my package

What am I doing wrong?