写这篇文章解答BAIDU JSP贴吧一朋友的疑问,帖子贴出好几天了,没人搭理,与大家分享:帖子标题:在线求助,一个超简单的程序~!我就是不会~! 帖子内容:定义一接口,用于计算和输出规则图形的的面积和周长,然后定义类cricle,Rctangle类实现接口,分别用于求长方形的面积和周长;再定义实现一个使用两个类的程序解答:/* Source: Demo.java* Author: Tony Don* Site:Txdnet.Cn* Date:2008-11-19*/public class Demo{interface IGraphicsCalculator{public static final double PI = 3.1415;public abstract double doArea();public abstract double doPerimeter();}protected class Circle implements IGraphicsCalculator{double cr;public Circle(double cr){this.cr = cr ;}public double doArea(){ return PI*cr*cr ; }public double doPerimeter(){return 2*PI*cr ;}}protected class Rectangular implements IGraphicsCalculator{double rx, ry;public Rectangular(double rx, double ry){this.rx=rx; this.ry=ry;}public double doArea(){ return rx*ry ; }public double doPerimeter(){return 2*(rx+ry) ;}}public Demo(){}public static void main(String[] args){Demo d = new Demo();Circle c = d.new Circle(2.5) ;System.out.println("圆面积=" + c.doArea());System.out.println("圆周长=" + c.doPerimeter());Rectangular r = d.new Rectangular(1.5, 2);System.out.println("矩形面积=" + r.doArea());System.out.println("矩形周长=" + r.doPerimeter());}}     http://www.txdnet.cn/ShowEssay-2-1973-Txdnet.jsp

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