继承 矩形 正方形

矩形类  再编写一个正方形类继承矩形（注意super用法）

class Retangle 
{
	public Retangle(double l,double w)
	{length=l;
		width=w;}
		public double calcPerimeter()
	{return 2*length+2*width;}
		public double calcArea()
	{return length*width;}
		public void Show()
	{System.out.println("长为"+length+"宽为"+width+"的矩形");}
		protected double length;
		protected double width;
}
class Square extends Retangle
{
	public Square(double side)
	{super(side,side);}
	public double calcPerimeter()
	{return width*4;}
	public void Show()
	{System.out.println("边长为"+width+"的正方形");}

}
class Test1
{
	public static void main(String[] args) 
	{
		Square sq1=new Square(2.0);
		sq1.Show();
		System.out.println("正方形周长为"+sq1.calcPerimeter());
		
	}
}