//抽象类

public abstract class Shape {

public abstract void perimeter();

public abstract void area();

}

//矩形类

public class Rectangle extends Shape {

public double height;

public double width;

@Override

public void perimeter() {

// TODO Auto-generated method stub

System.out.println("矩形的周长是："+(height+width)*2);

}

@Override

public void area() {

// TODO Auto-generated method stub

System.out.println("矩形的面积是："+height*width);

}

}

//圆形类

public class Circle extends Shape {

public double radius;

public final double PI=Math.PI;

@Override

public void perimeter() {

System.out.println("圆形的周长是："+2*PI*radius);

}

@Override

public void area() {

System.out.println("圆形的面积是："+PI*radius*radius);

}

}

//测试类

import java.util.Scanner;

public class Test {

     public static void main(String[] args) {

     Scanner input=new Scanner(System.in);

    System.out.println("请输入矩形的长和宽：");

     Rectangle rec=new Rectangle();

     System.out.print("长：");

     rec.height=input.nextDouble();

     System.out.print("宽：");

     rec.width=input.nextDouble();

     rec.perimeter();

     rec.area();

     System.out.println("请输入圆的半径：");

     Circle cir=new Circle();

     cir.radius=input.nextDouble();

     cir.perimeter();

     cir.area();

     input.close();

     }

}

这是我自己写，就是对结果的精度没有做处理