public class Circle implements Shape
{
    private double radius;
    public Circle (double radius)
    {
        this.radius = radius;
    }
    public double area()
    {
        return Math.PI*radius*radius;
    }    
    public double diameter()
    {
        return 2*radius;
    }    
    public double perimeter()
    {
        return 2*Math.PI*radius;
    }    
    @Override 
    public String toString()
    {
        return String.format("Circle(%s)", radius);
    }
}