public class Circle implements Shape {

	private double radius;

	public static final double PI = 3.14159;

	private static int numCirclesCreated = 0;


	public Circle(double radius) throws Exception {

		if(radius <=0)
		    throw new IllegalArgumentException();

		numCirclesCreated++;
		this.radius = radius;
	}

	public static int getNumCircles() {
		return numCirclesCreated;
	}


	public double perimeter() {
		return circumference();

	}


	public double circumference() {
		return 2 * PI * radius;

	}


	public double area() {

		return PI * Math.pow(radius, 2);
	}













}