Question

JAVA: This is my code, but when it runs, for the "Average Score" output, it only gives me NaN. How can I fix that?

import java.util.Scanner;

public class prog4 {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);

String name;
double score;
double minScore = 0;
double maxScore = 0;
int numberOfRecords = 0;
double sum = 0;
double average = sum / numberOfRecords;

System.out.printf("%-15s %-15s %-15s\n", "Student#", "Name", "Score");
  
       while (reader.hasNext()) {
name = reader.next();
score = reader.nextDouble();
sum += score;
System.out.printf("%8d%12s %16.2f\n", numberOfRecords + 1, name, score);
if (numberOfRecords == 0) {
minScore = score;
} else if (minScore > score) {
minScore = score;
}
if (maxScore < score) {
maxScore = score;
}
numberOfRecords += 1;
}

System.out.println("Number of Records: " + numberOfRecords);
System.out.printf("Max Score: %.2f\n", maxScore);
System.out.printf("Min Score: %.2f\n", minScore);
System.out.printf("Average Scores: %.2f\n", average);

}

}

Answer 1

Problem is with that average is being calculated before reading and processing scores. There is a need of change at two lines of code.

Modified lines are highlighted using BOLD case.

Update Program:

import java.util.Scanner;

public class prog4 {
   public static void main(String[] args) {
    Scanner reader = new Scanner(System.in);

        String name;
        double score;
        double minScore = 0;
        double maxScore = 0;
        int numberOfRecords = 0;
        double sum = 0;
        double average;

        System.out.printf("%-15s %-15s %-15s\n", "Student#", "Name", "Score");
      
        while (reader.hasNext()) {
            name = reader.next();
            score = reader.nextDouble();
            sum += score;
            System.out.printf("%8d%12s %16.2f\n", numberOfRecords + 1, name, score);
            if (numberOfRecords == 0) {
                minScore = score;
            } else if (minScore > score) {
                minScore = score;
            }
            if (maxScore < score) {
                maxScore = score;
            }
            numberOfRecords += 1;
        }
      
       average = sum / numberOfRecords;

        System.out.println("Number of Records: " + numberOfRecords);
        System.out.printf("Max Score: %.2f\n", maxScore);
        System.out.printf("Min Score: %.2f\n", minScore);
        System.out.printf("Average Scores: %.2f\n", average);
    }
}

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Sample Output: