Reading csv file into 2-dimentional Array Java

Question

I'm trying to write a method to take a multiline csv file and return the contents of that file as an arraylist. My problem is, when I print the array lines, they appear to only have the contents of the very last line of the file. I'm suspecting it might be something about FileReader or BufferedReader that I don't know. Anyhow, here's the code:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;


public int[][] readCSV(String pFilename) throws NumberFormatException, IOException {




int[][] arr = new int[19][19];



    BufferedReader br = new BufferedReader(new FileReader(pFilename));   
    String line = " ";
    String [] temp;

    while ((line = br.readLine())!= null){ 
        temp = line.split(","); //split spaces

        for(int i = 0; i<arr.length; i++) {
            for (int j = 0; j<arr.length; j++) {    
                arr[i][j] = Integer.parseInt(temp[j]);
            }
        }

    }

    printArray(arr);
}

public static void printArray (int[][] arr) { 
         for (int i =0; i <arr.length; i++) {
          for (int j = 0; j < arr.length; j++) {
            System.out.print(arr[i][j]);
          }
          System.out.println("");
         }
    }   



    }

input

1,1,0,0,1,1,1,1,1,0,0,1,1,0,0,0,1,1,1
1,0,0,1,1,1,1,0,1,1,1,0,1,1,1,0,1,0,1
1,0,0,1,0,0,1,1,1,1,1,1,1,1,1,0,1,1,0
1,1,0,1,0,1,1,0,1,0,1,0,0,1,1,1,0,1,1
1,1,0,1,1,1,0,1,0,1,0,0,1,1,1,0,1,0,0
1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,0,1,1,1
1,1,1,0,0,0,1,1,1,0,1,1,1,1,1,0,1,0,1
0,1,1,1,1,1,1,1,1,1,0,0,1,1,1,0,1,1,1
1,1,1,1,1,0,0,1,1,1,1,0,1,0,0,1,1,0,1
1,1,1,0,1,1,1,0,1,0,1,1,1,1,0,1,1,1,1
0,0,1,1,1,1,1,0,0,1,0,1,1,0,1,1,0,1,0
1,0,0,0,1,1,1,1,1,1,1,1,0,1,1,1,1,0,0
1,1,1,1,1,1,1,1,1,1,0,1,1,1,0,1,1,1,1
1,0,1,0,1,1,1,1,1,1,0,1,1,1,1,1,0,1,1
1,1,1,0,1,1,0,1,1,0,1,1,1,0,1,1,0,1,0
1,0,0,1,1,1,0,1,1,1,0,1,1,1,0,0,1,1,0
1,1,1,0,1,0,1,1,1,0,1,1,1,1,1,1,1,1,1
0,1,0,0,1,1,0,1,0,1,1,1,0,1,1,0,1,1,1
1,1,0,0,1,1,1,1,1,1,0,0,1,1,0,1,0,1,0
0,1,1,1,0,0,1,1,1,1,1,1,0,1,0,1,1,1,0

print output

0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110
0111001111110101110

Answer 1

while ((line = br.readLine())!= null){ 
        temp = line.split(","); //split spaces

        for(int i = 0; i<arr.length; i++) {
            for (int j = 0; j<arr.length; j++) {    
                arr[i][j] = Integer.parseInt(temp[j]);
            }
        }

    }

That is because you are rewriting the whole array for every input line. So only the last one "survives".

You want to keep the i index tied to the current line number (just do a i++ for every iteration of the outer loop, don't nest another for loop).

Answer 2

I assume that your CSV rows and columns are fixed as you are using fixed array, if it is dynamic you should first calculate rows and columns and then initialize the array OR use better dynamic data structure.

There is mistake in the code as you are assigning repeated values to array.

Change it to:

BufferedReader br = new BufferedReader(new FileReader(pFilename));   
String line = " ";
String [] temp;

while ((line = br.readLine())!= null){ 
    temp = line.split(","); //split spaces

       for (int j = 0; j<temp.length; j++) {    
            arr[i][j] = Integer.parseInt(temp[j]);
        }
    i++;
}

Answer 3

This will work:

    public static int[][]  readCSV(String pFilename) throws NumberFormatException, IOException {




    int[][] arr = new int[20][19];



        BufferedReader br = new BufferedReader(new FileReader(pFilename));   
        String line = " ";

        int i = -1;
        while ((line = br.readLine())!= null && i < arr.length){ 
            String [] temp = line.split(","); //split spaces
            ++i;   

                for (int j = 0; j<arr[i].length; j++) {    
                    arr[i][j] = Integer.parseInt(temp[j]);
                }

        }

        printArray(arr);
        return arr;
    }

    public static void printArray (int[][] arr) { 
             for (int i =0; i <arr.length; i++) {
              for (int j = 0; j < arr[i].length; j++) {
                System.out.print(arr[i][j]);
              }
              System.out.println("");
             }
        }