定义一个类Rectangle，描述一个矩形，包含有长、宽两种属性（用length和width表示）和计算面积的方法（方面名定义为area）。

import java.util.Scanner;
public class Test_5_1Test {
    public static class Test1 {
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            double a = sc.nextDouble();
            double b = sc.nextDouble();
            double c = sc.nextDouble();
            Test_5_1Coboid co = new Test_5_1Coboid(a,b,c);
            System.out.printf("%.2f",co.Area());
            System.out.println();
            System.out.printf("%.2f",co.volume());
        }
    }
}

public class Test_5_1Rectangle {
    private double length;
    private double width;
    private double area;
   Test_5_1Rectangle(double length, double width){
       this.length = length;
       this.width = width;
   }
   public double Area(){
       area = length*width;
       return area;
   }
}

public class Test_5_1Coboid extends Test_5_1Rectangle {
    private double height;
    Test_5_1Coboid(double length, double width, double height){
        super(length,width);
        this.height = height;
    }
    public double volume(){
        return Area()*height;
    }
}