编写一个名为Octagon的类，它扩展Geometricobject类并实现Comparable,Cloneable接口。假设八边形八条边的边长都相等。它的面积可以用下面的公式计算： 面积=（2+4/

1. 题目
   编写一个名为Octagon的类，它扩展Geometricobject类并实现Comparable,Cloneable接口。假设八边形八条边的边长都相等。它的面积可以用下面的公式计算：
   面积=（2+4/sqrt(2))边长边长
   画出Octagon、Geometricobject、Comparable,Cloneable的UML图。编写一个测试程序，创建一个边长值为5的Octagon对象，然后显示它的面积和周长。使用clone方法创建一个新对象，并使用compareTo方法比较这两个对象。
2. 代码

package testoctagon;
/***1. @author shinan*/
abstract class Geometricobject{String color="white";boolean filled;java.util.Date dateCreated;public Geometricobject(){dateCreated=new java.util.Date(); }public Geometricobject(String color,boolean filled){dateCreated=new java.util.Date();this.color=color;this.filled=filled;}public String getColor(){return color;}public void setColor(String color){this.color=color;}public boolean isFilled(){return filled;}public void setFilled(boolean filled){this.filled=filled;}public abstract double getArea();public abstract double getPerimeter();
} 
class Octagon extends Geometricobject implements Comparable,Cloneable{double side=0;public Octagon(double side){this.side=side;}public double setSide(){return side;}public double getArea(){return side*side*(2+4/Math.sqrt(2));}public double getPerimeter(){return side*8;}public Object clone()throws CloneNotSupportedException{return super.clone();}public int compareTo(Object o){if(getArea()>((Octagon)o).getArea())return 1;else if (getArea()<((Octagon)o).getArea())return -1;else return 0;}        
}
public class TestOctagon {/*** @param args the command line arguments*/public static void main(String[] args)throws Exception{// TODO code application logic hereOctagon o=new Octagon(5);System.out.println(o.getArea());System.out.println(o.getPerimeter());//Octagon a=new Octagon(4);//Octagon a1=a;Octagon a2=(Octagon)o.clone();System.out.println(o.compareTo(a2));}
}

3. 运行结果截图
   

4. UML图