public class Main { // example for non-virtual function implementation    public double sum(Shape2D[] shapes) {        double total = 0;        for (int i = 0;  i < shapes.length; i++) {            if (shapes[i] instanceof Rectangle) {                total += ((Rectangle)shapes[i]).area();            } else if (shapes[i] instanceof Circle) {                total += ((Circle)shapes[i]).area();            } else if (shapes[i] instanceof Parallelogram) {                total += ((Parallelogram)shapes[i]).area();            } // modify source code here for new sub classes        }        return total;    }    public static void main(String[] argv) {        Shape2D[] data; // array of reference to Shape2D        data = new Shape2D[5]; // create array object        data[0] = new Rectangle(2.4, 3.8); // Polymorphism        data[1] = new Circle(3.9);        data[2] = new Parallelogram(3.5, 6.7, 10.2);        data[3] = new Rectangle(5.3, 7.2);        data[4] = new Circle(4.6);        System.out.println("Sum of all Shape2D is "+sum(data));     }}