11

package test;

import java.awt.*;
import java.applet.*;
abstract class Shapes
{
protected int x,y,k;
protected double m;
public Shapes(int x,int y,int k,double m)
{this.x=x; this.y=y;
this.k=k; this.m=m;
}
abstract public double getArea();
abstract public double getPerimeter();
}
class Rect extends Shapes
{ public double getArea()
{ return(k*m); }
public double getPerimeter()
{ return(2*k+2*m);}
public Rect(int x,int y,int width,int height)
{ super(x,y,width,height);}
}
class Triangle extends Shapes
{ public double getArea()
{return(Math.sqrt(m*( m-k)*( m-x)*(m-y)));}
public double getPerimeter()
{return(k+x+y);}
public Triangle(int baseA,int baseB,int baseC)
{ super(baseA, baseB, baseC,0);
//m充当了周长的一半
m= (baseA+ baseB+ baseC)/2.0;
}
}
class Circle extends Shapes
{ public double getArea()
//Math是java.lang包中的类，PI是静态其属性，其值为Π
{return(m* m *Math.PI);}
public double getPerimeter()
{return(2*Math.PI* m);}
public Circle(int x,int y,int width)
{
//m充当了半径的角色，k充当了直径
super(x,y, width, width/2.0);
}
}
public class file6_9 extends Applet
{
Rect rect=new Rect(5,15,25,25);
Triangle tri=new Triangle(5,5,8);
Circle cir=new Circle(13,90,25);
//增加两个方法，注意抽象类的声明为s，ab为字符串输出的坐标。
//getClass.getName是得到对象对应的类名。
private void drawArea(Graphics g,Shapes s,int a,int b)
{g.drawString(s.getClass().getName()+" Area"+s.getArea(),a,b);}
private void drawPerimeter (Graphics g,Shapes s,int a,int b)
{g.drawString(s.getClass().getName()+" Perimeter"+s.getPerimeter(),a,b);}
public void paint(Graphics g)
{ g.drawRect(rect.x,rect.y,rect.k,(int)rect.m); //1
drawArea (g,rect,50,35); //2
drawPerimeter(g,rect,50,55); //3
drawArea (g, tri,50,75); //4
drawPerimeter(g,tri,50,95); //5　
g.drawOval(cir.x-(int)cir.k/2,cir.y-(int)cir.k/2,cir.k,cir.k); //6
drawArea (g, cir,50,115); //7
drawPerimeter(g,cir,50,135); //8
}
}