How can I write this .txt file into a 2D int array and not receive a NumberFormatException?

Question

I have been attempting to save a 9x9 2D array of ints from a .txt file. I have been on this website for a very long time attempting to get this to work and after doing a ton of tweaking, I am very close to getting it. The only problem is that nothing saves to the array!

Here is my code:

import javax.swing.*;
import java.util.*;
import java.io.*;
import java.awt.*;


public class test {

public static void main(String[] args) throws IOException {


    int[][] thing = new int[9][9];
    int row = 0;
    int rows = 9;
    int columns = 9;


    File fin = new File("C:\\Users\\David\\workspace\\tester\\initial.txt");

    BufferedReader reader = null;

    try {
        reader = new BufferedReader(new FileReader(fin));
        String line = reader.readLine();
        int lineNum = 0;

        while (line != null) {
            lineNum++;
            System.out.println("line " + lineNum + " = " + line);
            line = reader.readLine();

            String [] tokens = line.split(",");
            for (int j=0; j<tokens.length; j++) {
                System.out.println("I am filling the row: " + row);
                thing[row][j] = Integer.parseInt(tokens[j]);
            }
            row++;
        }

        System.out.println("I am printing the array for testing purposes: ");
        for (int i=0; i < rows; i++) {
            for (int j = 0; j < columns; j++)
                System.out.print(thing[i][j]);
            System.out.println("");
        }
    } catch (IOException error) {

    } finally {
        if (reader != null) reader.close();
    }

}

}

I should say that I am doing this as a test for a sudoku game I am trying to create as a mere side project, I am just super frustrated.

This was also my first post on this site so go easy on me for the formatting. Thanks all!

Edit: I made the change codaddict told me too and now I get the output:

line 1 = 5 3 0 0 7 0 0 0 0
I am filling the row: 0
Exception in thread "main" java.lang.NumberFormatException: For input string: "6 0 0 1 9 5 0 0 0"
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at test.main(test.java:36)

Take into account that the debug line "I am filling the row:" doens't appear into the output... You read all the file and THEN you try to parse it. Change it to have all the read & write logic into the same loop. — Averroes
– Averroes, Commented Dec 14, 2012 at 12:07
You need to load the Sodoku field by a .txt? otherwise you should use a class for the whole Sodoku Structure and make it Serializable — SomeJavaGuy
– SomeJavaGuy, Commented Dec 14, 2012 at 12:12

codaddict · Accepted Answer · 2012-12-14 15:50:44Z

3

You are doing:

    while (line != null) {
        lineNum++;
        System.out.println("line " + lineNum + " = " + line);
        line = reader.readLine();
    }

    // At this point you've already reached the end of the file
    // and line is null, so you never go inside the next while.

    while (line != null) {
        // you need to split on space not comma
        String [] tokens = line.split(" ");
        for (int j=0; j<tokens.length; j++) {
            System.out.println("I am filling the row: " + row);
            thing[row][j] = Integer.parseInt(tokens[j]);
        }
        row++;
    }

To fix this you need to process each line in the outer while loop:

    while (line != null) {
        lineNum++;
        System.out.println("line " + lineNum + " = " + line);
        line = reader.readLine();

        String [] tokens = line.split(",");
        for (int j=0; j<tokens.length; j++) {
            System.out.println("I am filling the row: " + row);
            thing[row][j] = Integer.parseInt(tokens[j]);
        }
        row++;
    }

edited Dec 14, 2012 at 15:50

answered Dec 14, 2012 at 12:05

codaddict

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2 Comments

Dusquad Over a year ago

I now get a Number Format error. Exception in thread "main" java.lang.NumberFormatException: For input string: "6 0 0 1 9 5 0 0 0" at java.lang.NumberFormatException.forInputString(Unknown Source) at java.lang.Integer.parseInt(Unknown Source) at java.lang.Integer.parseInt(Unknown Source) at test.main(test.java:36)

codaddict Over a year ago

@Dusquad: Have edited my answer. You need to split the input string on space and not comma.

Victor Mukherjee · Accepted Answer · 2012-12-14 12:04:59Z

1

The string line is already null after exiting the first while loop and hence the second while loop is never executed, and hence no values get assigned to the array cells, the default value of int array cells being zero which gets printed. Insert the assigning part in the first loop to solve the problem.

answered Dec 14, 2012 at 12:04

Victor Mukherjee

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Comments

Srinivas B · Accepted Answer · 2012-12-14 12:06:13Z

0

you have read the whole file in the first while loop itself.

So, you are unable to print the values in the second loop.

Make sure you are storing the values from the text file in the first while loop.

while (line != null) {
    lineNum++;
    System.out.println("line " + lineNum + " = " + line);
    line = reader.readLine();

    String [] tokens = line.split(",");
    for (int j=0; j<tokens.length; j++) {
        System.out.println("I am filling the row: " + row);
        thing[row][j] = Integer.parseInt(tokens[j]);
    }
    row++;
}

answered Dec 14, 2012 at 12:06

Srinivas B

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