java两个非常好的int被除掉，仍然返回0

Question

尝试使用我的sumDanceScore方法，将我的danceScore数组中的每个元素除以sumDanceScore的返回值；然而，当它继续返回0时。我放置了println来表示有两个合法整数，但它总是==0，请帮助

 package javasandbox;
 import java.util.*;


 public class JavaSandbox {


public static int sumDanceScore(int danceScore[], int first, int last)
 {


    if (first > last) 
     {
      return 0;
     }
   else
    {
      int total = sumDanceScore(danceScore,first+1,last) + danceScore[first];
      return total;
   }
}

   public static void main(String[] args)
 {


    Scanner kbd = new Scanner(System.in);
    System.out.println("Enter number of contestants : ");
    int numContest = kbd.nextInt();
    int danceScore[] = new int[numContest + 1];
    int first = 0;
    int last = danceScore.length - 1;
    System.out.println("Enter dance scores: ");

    int numContestIndex;
    for (numContestIndex = 1; numContestIndex <= numContest; numContestIndex++) 
    {
         danceScore[numContestIndex] = kbd.nextInt();
    }
    int danceScoreTotal = sumDanceScore(danceScore, first, last);
    System.out.println("SUM DANCE SORE METHOD: "+danceScoreTotal);

    for(int danceScoreIndex = 1; danceScoreIndex <= danceScore.length-1; danceScoreIndex++)
    {
        System.out.println("DANCE SCORE INDEX NUMBER: "+danceScore[danceScoreIndex]);
        int danceScoreShare = danceScore[danceScoreIndex] /  danceScoreTotal;
        System.out.println("DANCER SHARE PERCENT: "+danceScoreShare);
    }
} 

}

Answer 1

很明显，当我的danceScore数组中的每个元素除以the bigger return value of sumDanceScore时，由于int/int除法，返回值肯定是0

规则说在分子/分母除法中， 如果分子<；分母，则由于int中的截断，结果将为0

int(smaller)/int(bigger_sum) ~= 0.some_value = 0 (in terms of result as int)

例如：

4/20 = 0.20(in double) = 0 (for int result).

解决方法是使用float/double作为除法变量的数据类型

Answer 2

您需要先将int强制转换为浮点数（float或double）danceScoreShare是一个分数，所以它也应该是float或double

double danceScoreShare = (double)danceScore[danceScoreIndex] /  (double)danceScoreTotal;

你的danceScoreTotal总是比danceScore[danceScoreIndex]大，所以用java整数除法你总是会得到一个0的结果

^†实际上，你可以直接使用其中一个右手参数，而二进制数字升级会使用另一个参数

该technical details from the JLS

... the quotient produced for operands n and d that are integers after binary numeric promotion (§5.6.2) is an integer value q whose magnitude is as large as possible while satisfying |d · q| ≤ |n|.

例如，使用除法9 / 10，可以看到|10 · 1| = 10大于|9|。因此它返回0