20172319 2018.04.11 《Java程序设计教程》第7周课堂测验（补写博客）

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20172319 2018.04.11 《Java程序设计教程》第7周课堂测验

课程:《程序设计与数据结构》
班级：1723
学生：唐才铭
学号：20172319
指导老师：王志强
日期：2018.04.11
必修/选修：必修

实现接口的类要在类声明头部使用保留字implements，接着再给出接口名。在RationalNumber类的头部尾端加上implements Comparable<RationalNumber2>声明要实现Comparable接口。
public class RationalNumber2 implements Comparable<RationalNumber2>
若类声明要实现某个接口，必须提供实现这个接口中所有方法的实现代码。因此，要完整地实现接口需要在RationalNumber2类中提供实现接口中所有方法的代码。public int compareTo(RationalNumber2 op2)

将RationalNumber2中的对象数值转化为浮点值，再与定义好的误差标准比较（理由:参考week5学习总结中的浮点数值比较时的较好方法)。

double n1, n2, difference;

  n1 = (double) numerator / denominator;
  n2 = (double) op2.getNumerator() / op2.getDenominator();
  difference = Math.abs(n2 - n1);
  if(difference < 0.0001)
     return -1;
  else
     if (difference > 0.0001)
        return 1;
     else
        return 0;

测试程序代码

public class RationalTester2
{
   //----------------------------------------------------------------------
   // Creates some rational number objects and performs various
   // operations on them.
   //----------------------------------------------------------------------
   public static void main(String[] args)
   {
      RationalNumber2 r1 = new RationalNumber2(1, 3);
      RationalNumber2 r2 = new RationalNumber2(1, 9);
      RationalNumber2 r3, r4, r5, r6, r7;

      System.out.println("First rational number: " + r1);
      System.out.println("Second rational number: " + r2);
      if (r1.isLike(r2))
          System.out.println("r1 and r2 are equal.");
      else
          System.out.println("r1 and r2 are NOT equal.");

      if (r1.compareTo(r2) == 1 )
            System.out.println(" r1 > r2 ");
        else
            if (r1.compareTo(r2) ==-1)
            System.out.println(" r1 < r2 ");
        else
            System.out.println("r1 = r2");

      r3 = r1.reciprocal();
      System.out.println("The reciprocal of r1 is: " + r3);

      r4 = r1.add(r2);
      r5 = r1.subtract(r2);
      r6 = r1.multiply(r2);
      r7 = r1.divide(r2);

      System.out.println("r1 + r2: " + r4);
      System.out.println("r1 - r2: " + r5);
      System.out.println("r1 * r2: " + r6);
      System.out.println("r1 / r2: " + r7);

   }
}