public class Client {
 ...
 public double calculateArea(Object shape) {
     double area = 0;
     if (shape instanceof Square) {
         Square square = (Square) shape;
         area = square.getA() * square.getA();
     }
     else if (shape instanceof Rectangle) {
         Rectangle rectangle = (Rectangle) shape;
         area = rectangle.getA() * rectangle.getB();
     }
     else if (shape instanceof Circle) {
         Circle circle = (Circle) shape;
         area = Math.PI * cirle.getR() * cirle.getR();
     }
     return area;
 }

 public double calculatePerimeter(Object shape) {
     double perimeter = 0;
     if (shape instanceof Square) {
         Square square = (Square) shape;
         perimeter = 4 * square.getA();
     }
     else if (shape instanceof Rectangle) {
         Rectangle rectangle = (Rectangle) shape;
         perimeter = 2 * (rectangle.getA() + rectangle.getB());
     }
     else if (shape instanceof Circle) {
         Circle circle = (Circle) shape;
         perimeter = 2 * Math.PI * cirle.getR();
     }
     return perimeter;
 }
}