java 接口实现多态

package unit4;

import java.awt.Graphics;

public interface Shape {

    void drowme(Graphics g);

    double area();

    double length();

    String getName();

}

package unit4;

import java.awt.Graphics;

public class Point implements Shape{

    int x,y;

    Point (int x,int y){this.x=x;this.y=y;}

    public double area() {

        // TODO Auto-generated method stub

        return 0;

    }

    public void drowme(Graphics g) {

        g.fillOval(x,y,5,5);

    }

    public String getName() {

        // TODO Auto-generated method stub

        return "Point";

    }

    public double length() {

        // TODO Auto-generated method stub

        return 0;

    }

}

package unit4;

import java.awt.Graphics;

public class Triangle implements Shape {

    Point a,b,c;

    public Triangle(Point aa,Point bb,Point cc) {

        // TODO Auto-generated constructor stub

        a=aa;

        b=bb;

        c=cc;

    }

    public double area() {

        double a_b=Math.sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));

        double a_c=Math.sqrt((a.x-c.x)*(a.x-c.x)+(a.y-c.y)*(a.y-c.y));

        double b_c=Math.sqrt((b.x-c.x)*(b.x-c.x)+(b.y-c.y)*(b.y-c.y));

        double l=(a_b+a_c+b_c)/2;

        double s=Math.sqrt((l-a_b)*(l-b_c)*(l-a_c)*l);

        return s;

    }

    public void drowme(Graphics g) {

        g.drawLine(a.x,a.y,b.x,b.y);

        g.drawLine(a.x,a.y,c.x,c.y);

        g.drawLine(b.x,b.y,c.x,c.y);

    }

    public String getName() {

        return "triangle";

    }

    public double length() {

        double a_b=Math.sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));

        double a_c=Math.sqrt((a.x-c.x)*(a.x-c.x)+(a.y-c.y)*(a.y-c.y));

        double b_c=Math.sqrt((b.x-c.x)*(b.x-c.x)+(b.y-c.y)*(b.y-c.y));

        double l=(a_b+a_c+b_c);

        return l;

    }

}

package unit4;

import java.awt.Graphics;

public class Circl implements Shape {

    Point c;

    int r;

    public Circl(Point cc,int rr) {

        c=cc;

        r=rr;

    }

    public double area() {

        return 3.14159*r*r;

    }

    public void drowme(Graphics g) {

        g.drawOval(c.x-r,c.y-r,2*r,2*r);

    }

    public String getName() {

        return "circle";

    }

    public double length() {

        return 2*3.14159*r;

    }

}

package unit4;

import java.awt.Graphics;

public class Rect implements Shape{

    Point a,b;

    Rect(Point aa,Point bb){a=aa;b=bb;}

    public double area() {

        return (a.x-b.x)*(a.y-b.y);

    }

    public void drowme(Graphics g) {

        g.drawRect(a.x,a.y,b.x-a.x,b.y-a.y);

    }

    public String getName() {

        return "rectangle";

    }

    public double length() {

        return (b.x-a.x)*2+(b.y-a.y)*2;

    }

}

package unit4;

import java.applet.Applet;

import java.awt.Graphics;

public class Shapetest extends Applet{

     Shape[]myshapes=new Shape[5];

    public  void init() {

         Point a0=new Point(50,50);

         Point a1 = new Point(24,24);

         Point a2=new Point(100,200);

         Point a3 = new Point(200,120);

         myshapes[0]=a0;

         myshapes[1]=new Triangle(a1,a2,a3);

         myshapes[2]=new Circl(a2,50);

         myshapes[3]=new Circl(a3,100);

         myshapes[4]=new Rect(new Point(100,100),new Point(200,200));

    }

    public void paint(Graphics g){

        for(int i=0;i<myshapes.length;i++){

            myshapes[i].drowme(g);

            System.out.println(myshapes[i].getName()+": area: "+myshapes[i].area()+", length: "+myshapes[i].length());

        }

    }

}

这里可以直接在eclipse上运行位applet，但是，我发现一个严重的问题，我没法部署网站，哎，先不管了，以后用到了在慢慢调吧。

每次都要费老大劲配置。我日。。

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

    <applet code="shapetest.class" width=400 height=400>

    </applet>

</body>

</html>

理论上，配置成功可以在网页上启动小程序的。

巴特西

java 接口实现多态

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