Question

我正在尝试学习java while循环。我正在尝试制作一个程序，该计划将计算一组学生的考试成绩，并输出输入的总分数，分数高于69的通过考试的数量，并显示通过的考试的百分比。

我遇到的问题是我似乎无法正确输出百分比。它一直显示0.0。以下是我到目前为止提出的最佳代码。

嵌套while循环是不是很好的编码风格？是否有更简单的方法来缩短我的计划？感谢

    import java.util.Scanner;
    import java.text.DecimalFormat;

    public class CountPassingScores {

     public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        // Formats the percentage output to one decimal place.
        DecimalFormat df = new DecimalFormat("###,##0.0");

        // counts how many times a score is entered. Passing score is not
        // considered here.
        int count = 0;
        // The score the user enters.
        int score = 0;
        // percent of the class that passed the test. Passing score is 70 and
        // above.
        double percentOfClassPassed = 0.0;
        // total number of tests passed. Passing score is 70 and above.
        int numberOfTestsPassed = 0;

        System.out.println("This program counts the number of passing "
                + "test scores. (-1 to quit)\n");

        while (score != -1) {
            System.out.print("Enter the first test score:  ");
            score = scan.nextInt();

            while (count != -1 && score > 0) {
                System.out.print("Enter the next test score:  ");
                score = scan.nextInt();
                count++;

                if (count == -1)
                    break;
                else if (score > 69)
                    numberOfTestsPassed++;
                percentOfClassPassed = (numberOfTestsPassed / count);
            }

        }

        System.out.println("\nYou entered " + count + " scores.");
        System.out.println("The number of passing test scores is "
                + numberOfTestsPassed + ".");
        System.out.println(df.format(percentOfClassPassed)
                + "% of the class passed the test.");
    }
}

Answer 1

那是因为您要将int与int分开。这将导致仅int。

要获得正确的结果，请将任何一个投放到double。

percentOfClassPassed = ((double) numberOfTestsPassed / count);

Answer 2

您的代码并未考虑92作为测试通过分数，因为您没有在第一个while循环中增加numberOfTestsPassed的值。以下是我在您的代码段中所做的一些更改：

    while (score != -1) {
        System.out.print("Enter the first test score:  ");
        score = scan.nextInt();
        if(score > 69)
        numberOfTestsPassed++;
        while (count != -1 && score > 0) {
            System.out.print("Enter the next test score:  ");
            score = scan.nextInt();
            count++;
            if (score == -1)
                break;
            else if (score > 69)
                numberOfTestsPassed++;
        }
         percentOfClassPassed = ((double)numberOfTestsPassed * 100 / count); 
    }

它为所有输入提供正确的输出。

在我的while循环中查找百分比无法正常工作。嵌套时是否循环ok？

2 个答案: