// Shape class
              class Shape {
              public double getArea() {
              return 0; // Default implementation for unknown shapes
              }
              }
              
              // Rectangle subclass extending Shape
              class Rectangle extends Shape {
              private double length;
              private double width;
              
              public Rectangle(double length, double width) {
              this.length = length;
              this.width = width;
              }
              
              @Override
              public double getArea() {
              return length * width; // Calculate area of rectangle
              }
              }
              
              class Inheritance3 {
              public static void main(String[] args) {
              Shape shape = new Shape(); // Creating an instance of Shape (will use default getArea())
              
              Rectangle rectangle = new Rectangle(20, 40); // Creating an instance of Rectangle
              double rectangleArea = rectangle.getArea(); // Calculating area of rectangle
              
              System.out.println("Area of a shape (default): " + shape.getArea());
              System.out.println("Area of a rectangle: " + rectangleArea);
              }
              }