interface Shape {

  double area();

}

class Circle implements Shape {

  private double radius;

  Circle(double radius) {

      this.radius = radius;

  }

  @Override

  public double area() {

      return Math.PI * radius * radius;

  }

}

class Rectangle implements Shape {

  private double length;

  private double width;

  Rectangle(double length, double width) {

      this.length = length;

      this.width = width;

  }

  @Override

  public double area() {

      return length * width;

  }

}

public class ShapeAreaCalculator {

  public static void main(String[] args) {

      Shape circle = new Circle(5);

      Shape rectangle = new Rectangle(4, 6);

      System.out.println("圓形面積: " + circle.area());

      System.out.println("矩形面積: " + rectangle.area());

  }

}interface Shape { double area(); }

class Circle implements Shape { private double radius;





Circle(double radius) {

   this.radius = radius;

}

@Override

public double area() {

   return Math.PI * radius * radius;

}





}

class Rectangle implements Shape { private double length; private double width;





Rectangle(double length, double width) {

   this.length = length;

   this.width = width;

}

@Override

public double area() {

   return length * width;

}





}

public class ShapeAreaCalculator { public static void main(String[] args) { Shape circle = new Circle(5); Shape rectangle = new Rectangle(4, 6);





System.out.println("圓形面積: " + circle.area());

   System.out.println("矩形面積: " + rectangle.area());

}





}