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I am trying to write a program that reads a txt file and prints out its 2d numbers only array, but i got NullPointerEexception I have no idea why, please help

Here is my code:

import java.io.*;
import java.util.*;

public class FileR {
    public static void  main(String[] args) throws Exception {
        int[][] desktop;
        int rows = getTotalRow();
        desktop = new int[rows][];
        Scanner fin;
        InputStream is;
        is = new FileInputStream("hello.txt");
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        String line = "";
        try {
            int row = 0;
            while ((line = br.readLine()) != null) {
                line = line.replaceAll("[^0-9]+", "");
                if (line.isEmpty())
                    continue;
                String[] nums = line.split("\\s*(|,|\\s)\\s*");
                desktop[row] = new int[nums.length];
                for (int i = 0; i < nums.length; i++) {
                    desktop[row][i] = Integer.parseInt(nums[i]);
                }
                row++;

            }

        } catch (NumberFormatException e) {
            e.printStackTrace();
        }
        print(desktop);
    }


    public static int getTotalRow() throws IOException {
        LineNumberReader reader = null;
        try {
            reader = new LineNumberReader(new FileReader("hello.txt"));
            while ((reader.readLine()) != null) ;
            return reader.getLineNumber();
        } catch (Exception ex) {
            return -1;
        } finally {
            if (reader != null)
                reader.close();
        }
    }


    public static void print(int[][] value) {
        for (int i = 0; i < value.length; i++) {
            for (int j = 0; j < value[i].length; j++) {

                System.out.print(value[i][j] + " ");

            }
            System.out.println();
        }
    }
}

HEre is my hello txt file: 

There should be a specific text at the top of each page

2  2, 2, 2, 2, 2, 2, 2, 2, 2
2, 0, 0, 0, 0, 0, 0, 0, 0, 2
2, 0, 0, 0, 0, 0, 0, 0, 0, 2
2, 0, 0, 0, 0, 0, 0, 0, 0, 2
2, 0, 0, 1, 3, 4, 0, 0, 0, 2
2, 0, 0, 0, 3, 4, 0, 0, 0, 2
2, 0, 0, 0, 0, 0, 0, 0, 0, 2
2, 0, 0, 0, 0, 0, 0, 0, 0, 2
2, 0, 0, 0, 0, 0, 0, 0, 0, 2
2, 2, 2, 2, 2, 2, 2, 2, 2, 2
lmlmlm

my ouput :

2 2 2 2 2 2 2 2 2 2 
2 0 0 0 0 0 0 0 0 2 
2 0 0 0 0 0 0 0 0 2 
2 0 0 0 0 0 0 0 0 2 
2 0 0 1 3 4 0 0 0 2 
2 0 0 0 3 4 0 0 0 2 
2 0 0 0 0 0 0 0 0 2 
2 0 0 0 0 0 0 0 0 2 
2 0 0 0 0 0 0 0 0 2 
2 2 2 2 2 2 2 2 2 2 
Exception in thread "main" java.lang.NullPointerException
    at FileR.print(FileR.java:55)
    at FileR.main(FileR.java:34)

I guess NullPointerException caught when it loops empty string or null object, i want to omit null object but how to realize it i don't know Any idea on how to solve it?

Talgartbek Sarkeev
  • 73
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  • Well, but it is still obscure on my situations – Talgartbek Sarkeev Feb 14 '20 at 08:25
  • 1
    so is your question. You claim the Exception is thrown during a method "reads" which isn't in your code, you don't show any stacktrace (just a small part), you don't point to the line it is thrown on, .. – Stultuske Feb 14 '20 at 08:29
  • Sorry, i found that Exception is thrown during print method() when it loops empty sting or null object, i mean, when line = line.replaceAll("[^0-9]+", ""); and if there is a empty string, excepttion caught – Talgartbek Sarkeev Feb 14 '20 at 08:33
  • that line isn't in the print method, and that line won't throw an NPE. – Stultuske Feb 14 '20 at 08:35

1 Answers1

2

The problem is in your method getTotalRow() it is returning the wrong count.

public class FileR {
    public static String filePath = "hello.txt";

    public static void main(String[] args) throws Exception {
        int[][] desktop;
        int rows = getTotalRow();
        desktop = new int[rows][];
        Scanner fin;
        InputStream is;
        is = new FileInputStream(filePath);
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        String line = "";
        try {
            int row = 0;
            while ((line = br.readLine()) != null) {
                line = line.replaceAll("[^0-9]+", "");
                if (line.isEmpty())
                    continue;
                String[] nums = line.split("\\s*(|,|\\s)\\s*");
                desktop[row] = new int[nums.length];
                for (int i = 0; i < nums.length; i++) {
                    desktop[row][i] = Integer.parseInt(nums[i]);
                }
                row++;

            }

        } catch (NumberFormatException e) {
            e.printStackTrace();
        }
        print(desktop);
    }

    public static int getTotalRow() throws IOException {
        BufferedReader br = null;
        String line;
        int count = 0;
        try {
            br = new BufferedReader(new InputStreamReader(new FileInputStream(filePath)));
            while ((line = br.readLine()) != null) {
                boolean isDigit = !line.isEmpty() && Character.isDigit(line.charAt(0));
                if (isDigit) {
                    count++;
                }
            }
        } catch (Exception ex) {
            return -1;
        } finally {
            if (br != null)
                br.close();
        }

        return count;
    }

    public static void print(int[][] value) {
        for (int i = 0; i < value.length; i++) {
            for (int j = 0; j < value[i].length; j++) {

                System.out.print(value[i][j] + " ");

            }
            System.out.println();
        }
    }
}
Dinesh Shekhawat
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