How to fill a 2d character array with characters from a text file

Question

I need to take characters from a text file and store them row major order in a 2D character array that is 20 by 45. I will then need to print out the stored characters column major. This needs to work with any size text file. This code is as far as I have gotten and I haven't been able to print it out column major yet.

package myfirstjavaproject;

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

public class temp {
    public static void main(String[] args)throws Exception{
        File file = new File ("test.txt");
        BufferedReader br = new BufferedReader(new FileReader(file)); 
        String st = br.readLine();  


        int row = 20, column = 45;
        int offset = 0;
        char[][] array = new char [row][column];
        for (int i = 0; i < row; i++) {
            for(int j = 0; j < column; j++) {
                array[i][j] = st.charAt(offset++);
                System.out.print(array[i][j]);
            }
            System.out.println();
        }

    }

}

This code prints it out and then I get an error message.

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 55
    at java.lang.String.charAt(Unknown Source)
    at myfirstjavaproject.temp.main(temp.java:18)

Is the entire text file one line? (Hint: If not then you'll need to call `readLine()` more than once) — GBlodgett, Jan 21 '19 at 05:21
20 by 45 is a misleading expression. 20 rows by 45 characters or 20 characters by 45 rows? — Mad Physicist, Jan 21 '19 at 05:22
@GBlodgett I guess Im not understanding what yo mean by calling readLine() again — TBink, Jan 21 '19 at 05:26
Does you text file contain more than one line? If so then `st` will only be a single line and when you try to iterate over the entire file from that one line you'll get an out of bounds exception — GBlodgett, Jan 21 '19 at 05:31
It does have more than one line. How do I call readLine() again? — TBink, Jan 21 '19 at 05:35
Your file does not have so many data that write in Array. Either reduce your 2D Array size or put sufficient data in file. — Mostch Romi, Jan 21 '19 at 05:41

score 0 · Answer 1 · answered Jan 21 '19 at 05:46

/* I think you are trying below: Instead of String you might wanna use stringbuilder or stringbuffer */

  public static void main(String[] args)throws Exception{
        File file = new File ("test.txt");
        BufferedReader br = new BufferedReader(new FileReader(file)); 
        String st = br.readLine();  
        String s = null;
        while(br.read()!=-1)
        {
             s=s+br.readLine();
        }

        int row = 20, column = 45;
        int offset = 0;
        char[][] array = new char [row][column];
        for (int i = 0; i < row; i++) {
            for(int j = 0; j < column; j++) {
                array[i][j] = s.charAt(offset++);
                System.out.print(array[i][j]);
            }
            System.out.println();
        }

    }

score 0 · Answer 2 · edited Jan 21 '19 at 07:02

0

It might be that st.length is not long enough.

if (st != null && st.length() < offset) {
    st = br.readLine();
}

edited Jan 21 '19 at 07:02

Jeremy Walters

2,081
16
28

answered Jan 21 '19 at 05:50

Hill Hubery

1
1

How to fill a 2d character array with characters from a text file

2 Answers2