Read file into array returns wrong elements

Question

I'm attempting to take an input from the user, then if it matches one of the existing files, read the file and put the words, letters, or number into an array. The "words", and "alphabet" files seem to work fine, but the "numbers" is giving me an issue. It finds the file, reads it, puts it into an array, and gives the summation of the numbers; however, the output of the array is every other number, as opposed to all numbers, like it should be doing.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;

public class fileIO
{
    public static void main (String[] args) throws FileNotFoundException
    {
        String filename;
        System.out.println("Please enter name of file (alphabet,words,numbers): ");
        Scanner input = new Scanner(System.in);
        filename = input.nextLine();


        if(filename.equals("numbers"))
        {
            int sum = 0;
            Scanner reader = new Scanner(new File("/home/ninjew/workspace/FileIO/src/" + filename + ".txt"));
            ArrayList<Integer> arr = new ArrayList<Integer>();
            while(reader.hasNext())
            {
                arr.add(reader.nextInt());
                sum = sum + reader.nextInt();
            }
            System.out.println(arr);
            System.out.println("The summation is: " + sum);
            reader.close();
        }

        else if(filename.equals("words") || filename.equals("alphabet"))
        {
            Scanner reader = new Scanner(new File("/home/ninjew/workspace/FileIO/src/" + filename + ".txt"));
            // This is for words and letters within the file. Print words and letters.
            ArrayList<String> arr = new ArrayList<String>();

            while(reader.hasNext())
            {
                String line = reader.next();

                Scanner scanner = new Scanner(line);
                scanner.useDelimiter(",");
                while(scanner.hasNext()){
                    arr.add(scanner.next());
                }
                scanner.close();
            }
            System.out.println(arr);
            reader.close();

        }
    }
}

ControlAltDel · Accepted Answer · 2015-09-08 18:31:28Z

4

In if(filename.equals("numbers")) you are doing two reads from your file in this block, which is why it is skipping numbers

        while(reader.hasNext())
        {
            arr.add(reader.nextInt());
            sum = sum + reader.nextInt();
        }

Should be

        while(reader.hasNext())
        {
            int val = reader.nextInt();
            arr.add(val);
            sum = sum + val;
        }

answered Sep 8, 2015 at 18:31

ControlAltDel

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1 Comment

Tangwheeler Over a year ago

That worked perfect. Thanks for clearing that up for me!

Andreas · Accepted Answer · 2015-09-08 18:31:37Z

1

Your numbers reader loop is adding first number to the array and the next number to the sum.

If input is 1 2 3 4 5 6, your array is [1, 3, 5] and your sum is 2 + 4 + 6 = 12.

answered Sep 8, 2015 at 18:31

Andreas

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Comments

RP- · Accepted Answer · 2015-09-08 18:31:53Z

1

You are reading next two integers in one go. Every time you call scanner.nextInt() it will read a next int. You need to store nextInt in a temp variable and use it in both the places.

while(reader.hasNext())
            {
                int next = reader.nextInt();
                arr.add(next);
                sum = sum + next;
            }

answered Sep 8, 2015 at 18:31

RP-

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