Java上机实验4

1.设计一个抽象类图形类，在该类中包含有至少两个抽象方法求周长和求面积，分别定义圆形类、长方形类、矩形类来继承图形类，并实现上述两个方法。并创建实例验证。

2.package com.majing;
3.
4.public class test {
5.	public static void main(String[] args) {
6.		Roundness r = new Roundness(3);
7.		System.out.println(r.perimeter());
8.		System.out.println(r.area());
9.		
10.		Rectangle rec = new Rectangle(5,6);
11.		System.out.println(rec.perimeter());
12.		System.out.println(rec.area());
13.		
14.		Matrix m = new Matrix(12);
15.		System.out.println(m.perimeter());
16.		System.out.println(m.area());
17.	}
18.
19.}
20.
21.abstract class Graph {
22.	abstract double perimeter();
23.	abstract double area();
24.}
25.
26.class Roundness extends Graph
27.{
28.	private int radius;
29.	
30.	Roundness(int r)
31.	{
32.		radius = r;
33.	}
34.	
35.	double perimeter()
36.	{
37.		return 2*3.1415*radius;
38.	}
39.	
40.	double area()
41.	{
42.		return 3.14159*3.14159*radius;
43.	}
44.}
45.
46.class Rectangle extends Graph
47.{
48.