定义一个类，提供显示圆的周长的方法，提供显示圆的面积的方法

public class homework006{
	public static void main(String[] args) {
		Circle circle = new Circle();
		double r = 5;
		System.out.println("圆的周长为" + circle.zhouchang(r));
		System.out.println("圆的面积为" + circle.mianji(r));
	}
}
class Circle{
	double r;//radius;
	double s;
	double c;
	
	public double zhouchang(double r){
		s = Math.PI * r * r;
		return s;
	} 
	public double mianji(double r){
		c = 2 * r * Math.PI;
		return c;
	}
}