java用接口、多态、继承、类计算三角形和矩形周长及面积的方法

 /** * @author vvv * @date 2013-8-10 上午08:56:48 */ package com.duotai; /** * * */ public interface Shape { public double area(); public double longer(); } /** * @author vvv * @date 2013-8-10 上午09:10:06 */ package com.duotai; /** * * */ public class Triangle implements Shape { double s1; double s2; double s3; // 初始化一个三角形对象，并赋予该三角形三边长 public Triangle(double s1, double s2, double s3) { if (isTri(s1, s2, s3)) { this.s1 = s1; this.s2 = s2; this.s3 = s3; } else { System.out.println("输入的三边长" + s1 + "、" + s2 + "、" + s3 + "不能组成一个三角形，请重新输入三边长！"); } } // 判断是否是个三<p style="color:transparent">来源gao!%daima.com搞$代*!码网</p>角形 public boolean isTri(double s1, double s2, double s3) { if (s1 + s2 <s3) { return false; } if (s1 + s3 <s2) { return false; } if (s2 + s3 <s1) { return false; } return true; } /* * (non-Javadoc) * * @see com.duotai.Shape#area() */ @Override public double area() { double p = (s1 + s2 + s3) / 2; return Math.sqrt(p * (p - s1) * (p - s2) * (p - s3)); } /* * (non-Javadoc) * * @see com.duotai.Shape#longer() */ @Override public double longer() { return s1 + s2 + s3; } } /** * @author vvv * @date 2013-8-10 上午09:12:06 */ package com.duotai; /** * * */ public class Director implements Shape { double s1; double s2; // 初始化一个长方形，并赋予该长方形两边长 public Director(double s1, double s2) { this.s1 = s1; this.s2 = s2; } /* * (non-Javadoc) * * @see com.duotai.Shape#area() */ @Override public double area() { // TODO Auto-generated method stub return s1 * s2; } /* * (non-Javadoc) * * @see com.duotai.Shape#longer() */ @Override public double longer() { // TODO Auto-generated method stub return 2 * (s1 + s2); } } /** * @author vvv * @date 2013-8-10 上午09:13:30 */ package com.duotai; /** * * */ public class Test { /** * @param args */ public static void main(String[] args) { Shape triangle = new Triangle(3, 4, 8); // 新建一个三边长为3，4，5的三角形 Shape tri = new Triangle(3, 4, 5); Shape director = new Director(10, 20); // 新建一个两边长为10,20的长方形 System.out.println("三角形triangle的周长为：" + triangle.longer()); System.out.println("三角形triangle的面积为：" + triangle.area()); System.out.println("三角形tri的周长为：" + tri.longer()); System.out.println("三角形tri的面积为：" + tri.area()); System.out.println("该长方形的周长为：" + director.longer()); System.out.println("该长方形的面积为：" + director.area()); } }