How to calculate the perimeter and area of ​​triangles and rectangles in Java using interfaces, polymorphism, inheritance, and classes

The examples in this article describe how Java uses interfaces, polymorphism, inheritance, and classes to calculate the perimeter and area of ​​triangles and rectangles. Share it with everyone for your reference. The details are as follows:

Define the interface specification:

/** 
 * @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()); 
  } 
}

I hope this article will be helpful to everyone’s java programming.

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