请问下面加粗代码为什么报错？
public class test {
public static void main(String[] args) {
System.out.println("请输入矩形的长和宽");
Shape rec=new Rectangle();
rec.perimeter();
rec.area();
System.out.println("请输入圆的半径");
Shape cir=new Circle();
cir.perimeter();
cir.area();
}
}
