package cn.edu.bjut.chapter4;

public class Circle2 {
	private double diameter; 
	
	public Circle2(double radius) {
		this.diameter = 2 * radius; 
	}
	
	public double getRadius() {
		return (diameter / 2);
	}

	public void setRadius(double radius) {
		this.diameter = radius * 2;
	}
	
	public double area() {
		return (Math.PI * diameter * diameter / 4); 
	}
	
	public double perimeter() {
		return (Math.PI * diameter); 
	}
}