Java 2D Array Print Issue

Question

So I've been looking over this for a while and can't seem to get by this issue...

Basically, there is a txt file that the user enters (max 50 rows and 20 integers in each) and I am converting that to a 2D int[][].

So, if the input is:

1 2 3 4 5 6
54 67 66
45
34 54 2

The 2D array should look like:

1  2  3  4  5  6
54 67 66 0  0  0
45 0  0  0  0  0
34 54 2  0  0  0

I am currently getting the following output:

[1, 2, 3, 4, 5, 6, 54, 67, 66, 45, 2, 3, 34, 54, 2, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

This would be fine except the numbers all go into the first row - which they shouldn't.

Here is my code (Functions class):

package com.company;

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

public class Functions {
    public int[][] readFile(File file) {

        try {

            Scanner scn = new Scanner(file);
            Scanner scn2 = new Scanner(file);

            //set initial count (of rows) to zero
            int maxrows = 0;

            //sets columns to 20 (every row has 20 integers - filled w zeros if not 20 inputted)
            int maxcolumns = 20;

            // goes through file and counts number of rows to set array parameters
            while (scn.hasNextLine()) {
                maxrows++;
                scn.nextLine();
            }

                // create array of counted size
                int[][] array = new int[maxrows][maxcolumns];

                //new scanner to reset
                Scanner scan1 = new Scanner(file);

                //places integer one by one into array
                for (int row = 0; row < maxrows; row++)
                    for (int column = 0; column < maxcolumns; column++) {
                        if (scan1.hasNext())
                            array[row][column] = scan1.nextInt();
                        else {
                            break;
                        }
                    }
                return array;
        }
        // general exception
        catch(Exception e){
            System.out.println("PROBLEM");
            e.printStackTrace();
            //returns null array
            return null;

        }

    }
}

Main Class:

package com.company;

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



public class Main {
    public static void main(String[] args) throws IOException {
        //Creates new class2 object
        Functions o = new Functions();
        //Creates new file object
        File file = new File("src/com/company/UserInput");
        //Takes in file object as parameter
        int[][] array = o.readFile(file);

        //prints as an array
        for (int i=0; i < array.length; i++)
            System.out.println(Arrays.toString(array[i]));
    }
}

Hint: don't use static mains to test your code. Learn about Junit; and write unit tests. — GhostCat
– GhostCat, Commented Mar 18, 2016 at 16:56
@FastSnail Thanks for catching that! It was just a typo- I had a different array earlier. — FΣynman
– FΣynman, Commented Mar 18, 2016 at 16:56

Maljam · Accepted Answer · 2016-03-18 17:00:10Z

3

The problem is in:

for (int row = 0 ; row < maxrows ; row++) {
    for (int column = 0 ; column < maxcolumns ; column++) {
        if (scan1.hasNext()) // ← *here*
            array[row][column] = scan.nextInt();
        else {
            break;
        }
    }
}

scan1.hasNext() will not stop at the end of the line, it will return true until it exhausts the whole file. Instead you should do something like that:

for (int row = 0 ; row < maxrows ; row++) {
    Scanner lineScan = new Scanner(scan1.nextLine());

    for (int column = 0 ; lineScan.hasNextInt() ; column++) {
        array[row][column] = lineScan.nextInt();
    }
}

answered Mar 18, 2016 at 17:00

Maljam

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1 Comment

FΣynman Over a year ago

Thank you so much!

rodrigo · Accepted Answer · 2016-03-18 17:46:52Z

0

When you use "scan1.nextInt();" you are ignoring the new line, because it, is all in a same row. What you can do is use:

Scanner scan1 = new Scanner(file).useDelimiter("\\||\\n");
while (scan1.hasNext()) {
                String nextValue = scan1.next();
                System.out.println("nextValue " + nextValue);
}

Them you have: nextValue 1 2 3 4 5 6 nextValue 54 67 66 nextValue 45 nextValue 34 54 2

You can split this line and do a manual control

answered Mar 18, 2016 at 17:46

rodrigo

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