Interfata.java

Interface.java

interface Shape {

     double calculateArea(); //public
     double calculatePerimeter();
}


class Circle implements Shape {

    double radius;

    Circle(double radius) {
       this.radius = radius;
    }

    @Override
    public double calculateArea() {
            return Math.PI * radius * radius;
    }

    @Override
    public double calculatePerimeter() {
            return 2 * Math.PI * radius;
    }
}


class Rectangle implements Shape {

    double width, height;

    Rectangle(double width, double height) {
       this.width = width;
       this.height = height;
    }

    @Override
    public double calculateArea() {
            return width * height;
    }

    @Override
    public double calculatePerimeter() {
            return 2 * (width + height);
    }
}

//O interfata este un CONTRACT care spune ce metode trebuie sa aiba o clasa, fara sa spuna cum sunt implementate.
//O forma pura de abstractizare
public class Interfata {

      public static void main(String[] args) {

           Shape c = new Circle(3);
           Shape d = new Rectangle(4,5);

           System.out.println("Cerc -> Arie: " + c.calculateArea() + ", Perimetru: " + c.calculatePerimeter());
           System.out.println("Dreptunghi -> Arie: " + d.calculateArea() + ", Perimetru: " + d.calculatePerimeter());
      }

}