Shape3.java

interface Shape {}

class Rectangle implements Shape {
  double x, y;
}

class Circle implements Shape {
  double radius;
}

static double circumference(Shape shape) {
  if (shape instanceof Rectangle) {
    Rectangle rectangle = (Rectangle) shape;
    return (rectangle.x + rectangle.y) * 2;
  } else if (shape instanceof Circle) {
    Circle circle = (Circle) shape;
    return 2 * PI * circle.radius;
  } else {
    throw new UnsupportedOperationException();
  }
}

static double area(Shape shape) {
  if (shape instanceof Rectangle) {
    Rectangle rectangle = (Rectangle) shape;
    return rectangle.x * rectangle.y;
  } else if (shape instanceof Circle) {
    Circle circle = (Circle) shape;
    return PI * circle.radius * circle.radius;
  } else {
    throw new UnsupportedOperationException();
  }
}

static Shape longestLine(Shape shape) {
  if (shape instanceof Rectangle) {
    Rectangle rectangle = (Rectangle) shape;
    return Math.sqrt(rectangle.x * rectangle.x + rectangle.y * rectangle.y);
  } else if (shape instanceof Circle) {
    Circle circle = (Circle) shape;
    return 2 * circle.radius;
  } else {
    throw new UnsupportedOperationException();
  }
}