Why is my code not printing anything to stdout?

Question

I'm trying to calculate the average of a student's marks:

import java.util.Scanner;

public class Average

{

    public static void main(String[] args)
    {
        int mark;
        int countTotal = 0;  // to count the number of entered marks
        int avg = 0;        // to calculate the total average
        Scanner Scan = new Scanner(System.in);

        System.out.print("Enter your marks: ");
        String Name = Scan.next();

        while (Scan.hasNextInt())
        {
            mark = Scan.nextInt();
            countTotal++;

            avg = avg + ((mark - avg) / countTotal);
        }


        System.out.print( Name + "  " + avg );
    } 
}

Answer 1

Because it's still sitting in the while loop, waiting for an instruction to break out of the loop.

Here's a Sun tutorial on the subject. The course materials you got should also contain this information by the way.

Answer 2

Hi WM,

In my previous post (previous answer) I indicated that you need to press Ctrl+D after you are done inputting numbers. Ctrl+D signals to your program that there is no more input.

Try entering:

WM 1 2 3 6

Then press Ctrl+D

Answer 3

You should use getline and accept an "exit" string. String.split and some of the Integer.valueOf stuff makes parsing numbers from string literals written in very easy in Java.

Answer 4

Here's a solution that uses two Scanner (as suggested in my previous answer).

• Scanner stdin = new Scanner(System.in); scans user's input
• Scanner scores = new Scanner(stdin.nextLine()); scans the line containing the scores

Note also that it uses a much simpler and more readable formula for computing the average.

        Scanner stdin = new Scanner(System.in);

        System.out.print("Enter your average: ");
        String name = stdin.next();

        int count = 0;
        int sum = 0;
        Scanner scores = new Scanner(stdin.nextLine());
        while (scores.hasNextInt()) {
            sum += scores.nextInt();
            count++;
        }
        double avg = 1D * sum / count;
        System.out.print(name + "  " + avg);

Sample output:

Enter your average: Joe 1 2 3
Joe  2.0

Answer 5

How about this?

import java.util.Scanner;

public class Average{

public static void main(String[] args)
{
    int mark = 0;
    int countTotal = 0;  // to count the number of entered marks
    int avg = 0;        // to calculate the total average
    Scanner scan = new Scanner(System.in);

    System.out.println("Enter student name: ");
    String name = scan.next();

    System.out.println("Please enter marks one by one?");


    while(scan.hasNextInt()){

        int tempMark = scan.nextInt();
        mark += tempMark;
        countTotal+=1;

        System.out.println("If you are done with mark, type \"Done!\"");
    }

    avg = mark/countTotal;

    System.out.print( name + "  " + avg );
} 

}