java - Read Data From Text File And Sum Numbers

Question

I want to read in data from a text file which is full of integers and have the program print those integers out to the screen while summing them. This shouldn't be hard, but I can't figure it out!!!

Here is the extremely simplified text file:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

And here is my code that is supposed to work:

import java.util.*;
import java.io.File;
import java.io.IOException;

public class ReadFile
{
    public static void main(String[] args)
    throws IOException
    {
        Scanner textfile = new Scanner(new File("Some_Numbers.txt"));

        filereader(textfile);
    }   


    static void filereader(Scanner textfile)
    {
        int i = 0;
        int sum = 0;

        while(i <= 19)
        {
            System.out.println(textfile.nextInt());
            sum = sum + textfile.nextInt();
            i++;
        }
    }



}

Finally, here is the output I get:

1
3
5
7
9
11
13
15
17
19
Exception in thread "main" java.util.NoSuchElementException
    at java.util.Scanner.throwFor(Scanner.java:838)
    at java.util.Scanner.next(Scanner.java:1461)
    at java.util.Scanner.nextInt(Scanner.java:2091)
    at java.util.Scanner.nextInt(Scanner.java:2050)
    at ReadFile.filereader(ReadFile.java:23)
    at ReadFile.main(ReadFile.java:12)

Answer 1

You never increment i, so the while loop continues beyond the end of the file. As for summing, do something like this.

static void addstuff(Scanner aScanner) {
        int sum = 0;

        while (aScanner.hasNextInt()) {
            sum += aScanner.nextInt();
        }

        System.out.println(sum);
}

This will run until hasNextInt() returns false, which occurs when the next item the scanner sees isn't an integer. This could be non-numeric input or the end of the file. This means you're no longer limited to 25 integers - it'll read as many as it can before stopping.