// CSE 143, Winter 2009, Marty Stepp
// A Circle object represents a 2D circle shape with a given radius.
public class Circle implements Shape {
    private double radius;
    
    // Constructs a new circle with the given radius.
    public Circle(double radius) {
        this.radius = radius;
    }
    
    // Returns the area of this circle.
    public double area() {
        return Math.PI * radius * radius;
    }
    
    // Returns the perimeter of this circle.
    public double perimeter() {
        return 2.0 * Math.PI * radius;
    }
}