Java学习——抽象类和接口简单实例（三角形面积、正方形面积）

1、首先定义抽象类：Figure

2、定义两个接口：Area，Perimeter

3、定义两个类：Sibian,Triangle

4、定义测试类：验证以上方法

抽象类：Figure

package com.testimplemnts; public abstract class Figure { public Figure(){} public abstract double area(); public abstract double perimeter(); }

Area 接口：

package com.testimplemnts; public interface Area { public double area(); } Perimeter接口 package com.testimplemnts; public interface Perimeter { public double perimeter(); }

Sibian类

package com.testimplemnts; public class SiBian extends Figure implements Area,Perimeter{ public double bian; public SiBian(double bian){ this.bian=bian; } public double area() { return bian*bian; } public double perimeter() { return 4*bian; } } Triangle类 package com.testimplemnts; public class Triangle extends Figure implements Area,Perimeter{ public double di,high,s1,s2; public Triangle(double di,double high) { this.di=di; this.high=high; } public Triangle(double di,double s1,double s2) { this.di=di; this.s1=s1; this.s2=s2; } public double area() { return di*high/2; } public double perimeter() { return di+s1+s2; } } 测试类 package com.testimplemnts; public class InitialTest { public static void main(String args[]){ SiBian si =new SiBian(4); double siarea =si.area(); double siperimeter =si.perimeter(); System.out.println("mianji is "+siarea+"zhouchang is "+ siperimeter); Triangle tr =new Triangle(3,4); Triangle tr1 =new Triangle(3,4,5); double trarea =tr.area(); double trperimeter =tr1.perimeter(); System.out.println("mianji is "+trarea+"zhouchang is "+trperimeter); } }