Question

我是Java新手，正在从事学校作业。当我运行该程序时，它将给出测试成绩的平均值，但是当我输入“ 999”退出时。它给了我一个平均值='NaN'，但我需要说0

import java.util.Scanner;

public class TestScoreApp {

    public static void main(String[] args) {
        // display operational messages
        System.out.println("Enter test scores that range from 0 to 100.");
        System.out.println("To end the program, enter 999.");
        System.out.println();  // print a blank line

        // initialize variables and create a Scanner object
        int scoreTotal = 0;
        int scoreCount = 0;
        int testScore = 0;
        Scanner sc = new Scanner(System.in);

        // get a series of test scores from the user
        while (testScore != 999) {
            // get the input from the user
            System.out.print("Enter score: ");
            testScore = sc.nextInt();

            // makes average score 0
            if (999 == testScore) {
                double averageScore;
            averageScore = 0;
        }
            // accumulate score count and score total
            if (testScore <= 100) {
                scoreCount = scoreCount + 1;
                scoreTotal = scoreTotal + testScore;
            } else
                System.out.println("Invalid entry: not counted"); 
        }


        // display the score count, score total, and average score

        double averageScore = (double) scoreTotal / scoreCount;
                if (averageScore == 0) {
                    System.out.println("0");
        } 
        String message = "\n"
                + "Score count:   " + scoreCount + "\n"
                + "Score total:   " + scoreTotal + "\n"
                + "Average score: " + averageScore + "\n";
        System.out.println(message);
    }
}

我已经在这个程序上工作了3个小时，我们将不胜感激。甚至重定向到已归档的帖子也将很有帮助。

Answer 1

您在999之前输入了其他分数吗？如果不是，您的scoreCount将为零，并且在计算平均值时将被零除。解决方案：在scoreTotal时不要将scoreCount除以scoreCount == 0。在这种情况下，平均值仅为零：

double averageScore = 0;
if (scoreCount != 0) 
    avergageScore = scoreTotal / scoreCount;

// or, if you like the ternary operator better:

double averageScore = 
    (scoreCount == 0) 
       ? 0 
       : (scoreTotal / scoreCount);

Answer 2

在进入double avarageScore循环之前，只需创建while。

import java.util.Scanner;

public class TestScoreApp {

    public static void main(String[] args) {
        // display operational messages
        System.out.println("Enter test scores that range from 0 to 100.");
        System.out.println("To end the program, enter 999.");
        System.out.println();  // print a blank line

        // initialize variables and create a Scanner object
        int scoreTotal = 0;
        int scoreCount = 0;
        int testScore = 0;
        Scanner sc = new Scanner(System.in);

        double averageScore;

并添加if(scoreCount==0){}条件以检查是否有以前的输入，因此它不会被零除零。

// get a series of test scores from the user
            while (testScore != 999) {
                // get the input from the user
                System.out.print("Enter score: ");
                testScore = sc.nextInt();

                // makes average score 0
                if (999 == testScore) {
                    //double averageScore;
                    averageScore = 0;
            }
                // accumulate score count and score total
                if (testScore <= 100) {
                    scoreCount = scoreCount + 1;
                    scoreTotal = scoreTotal + testScore;
                } else
                    System.out.println("Invalid entry: not counted"); 
            }

            // display the score count, score total, and average score
            if(scoreCount==0) {
               averageScore = 0;
            }else {
               averageScore = (double) scoreTotal / scoreCount;
            }
        } 

            String message = "\n"
                    + "Score count:   " + scoreCount + "\n"
                    + "Score total:   " + scoreTotal + "\n"
                    + "Average score: " + averageScore + "\n";
            System.out.println(message);
        }
    }

我在计算机上进行编译，结果为999

Enter test scores that range from 0 to 100.
To end the program, enter 999.

Enter score: 50
Enter score: 50
Enter score: 50
Enter score: 42
Enter score: 999
Invalid entry: not counted

Score count:   4
Score total:   192
Average score: 48.0

如果我第一次输入999，输出为：

Enter test scores that range from 0 to 100.
To end the program, enter 999.

Enter score: 999
Invalid entry: not counted

Score count:   0
Score total:   0
Average score: 0.0

正如诚诚指出的那样：“ NaN表示“不是数字”，并且是对浮点数进行未定义操作的结果，例如将零除以零。（请注意，将非零数字除以零也是通常在数学中未定义，它不会导致NaN，但会导致正无穷大或负无穷大”。

如果您将999输入为第一个输入，则会得到平均得分：NaN，因为它除以0/0。

尝试定义预定义的数据类型（覆盖）

2 个答案: