设计一个形状类Shape,方法:求周长和求面积 形状类的子类:Rect(矩形),Circle(圆形) Rect类的子类:Square(正方形)

package homework;
/*1.设计一个形状类Shape,方法:求周长和求面积
形状类的子类:Rect(矩形),Circle(圆形)
Rect类的子类:Square(正方形)
不同的子类会有不同的计算周长和面积的方法
创建三个不同的形状对象,放在Shape类型的数组里,
分别打印出每个对象的周长和面积*/

public class Shape {
double sum=0;//周长
double area=1;//面积

public double getGirth() {
return 0.0;
}
public double getArea() {
return 0.0;
}

public static void main(String[] args) {
// TODO Auto-generated method stub
Rect r=new Rect(3.0,4.0);
Circle c=new Circle(3.0);
Square s=new Square(4.0);
Shape[] shapes=new Shape[3];
shapes[0]=r;
shapes[1]=c;
shapes[2]=s;
for(int i=0;i<shapes.length;i++) {
System.out.println("周长为："+shapes[i].getGirth()+" "+"面积为："+shapes[i].getArea());
}
}
}

package homework;

public class Circle extends Shape{
final double a=3.14159265;
double radius;

public Circle(double radius) {
this.radius=radius;
}
public double getRadius() {
return radius;
}
public void setRadius(double radius) {
this.radius = radius;
}
public double getGirth() {
sum=2*a*radius;
return sum;
}
public double getArea() {
area=a*radius*radius;
return area;
}
public static void main(String[] args) {
// TODO Auto-generated method stub

}

}

package homework;

public class Rect extends Shape{
double length;//长
double wide;//宽
public Rect(double length,double wide) {
this.length=length;
this.wide=wide;
}
public Rect() {}

public double getLength() {
return length;
}

public void setLength(double length) {
this.length = length;
}

public double getWide() {
return wide;
}

public void setWide(double wide) {
this.wide = wide;
}

public double getGirth() {
sum=2*(this.length+this.wide);
return sum;
}
public double getArea() {
area=this.length*this.wide;
return area;
}
public static void main(String[] args) {
// TODO Auto-generated method stub

}

}

package homework;

public class Square extends Rect{
public Square(double length) {
this.length=length;
}
public double getGirth() {
sum=4*length;
return sum;
}
public double getArea() {
area=length*length;
return area;
}
public static void main(String[] args) {
// TODO Auto-generated method stub

}

}