Convert List to Array int[][]

Question

I need to read matrix from csv-file using OpenCSV library. Function readAll() from OpenCSV return List String[], while I need int[][]. This is what I have:

 cSVFileReader = new CSVReader(new FileReader(path), ',');
 List<String[]> allRows = cSVFileReader.readAll();

 for(String[] row : allRows){
   for (int i = 0; i<cSVFileReader.getLinesRead(); i++){
        String[] numbers = row[i].split(" ");
        int [] ary = new int[numbers.length];
        int j = 0;
        for (String number : numbers){
        ary[j++] = Integer.parseInt(number); 
         }
    }
 }

And this is output:

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:504)
at java.lang.Integer.parseInt(Integer.java:527)
at strassenalgorithm.CSVFile.readM(CSVFile.java:37)
at strassenalgorithm.Main.main(Main.java:26)

Seems like you're parsing an empty string into an integer. Shouldn't be difficult to debug. — Anindya Dutta, Jan 11 '17 at 20:01
You are trying to parse a blanck space to a number. Check first if the String is blank or null — Gatusko, Jan 11 '17 at 20:01
You would need to define a requirement for handling an EMPTY string and then only try to parse the strings which are not null and blank. StringUtils in Apache commons has utility method to check this. — Amit, Jan 11 '17 at 20:01

score 2 · Accepted Answer · answered Jan 11 '17 at 20:08

When you see a NumberFormatException, you need to decide if your input is wrong, or your code is wrong.

If your input is wrong, you need to add code that produces a nice-looking error at the top level, e.g.

try {
    parseMyFile();
} catch (NumberFormatException nfe) {
    System.err.println("File contains invalid numbers: "+nfe.getMessage());
}

If you want to allow this input, e.g. because it's OK to have empty strings in place of numbers, check for specific input, or catch NumberFormatException inside the loop:

for (String number : numbers){
    if (number.length() != 0) {
        ary[j++] = Integer.parseInt(number); 
    } else {
        ary[j++] = 0; // In this case, zero is the same as "empty"
    }
}

Did not check file I was working with. It included spaces. Thank you — Kat Roz, Jan 11 '17 at 20:25

score 0 · Answer 2 · answered Jan 12 '17 at 12:35

After solving problem with wrong input my code still didn't work, this time gave me ArrayIndexOutOfBoundsException. Maybe smn will have the same problem, so here is my solution.

private static int r;

public static int[][] readM(String path) throws FileNotFoundException, IOException {
   cSVFileReader = new CSVReader(new FileReader(path), ',');
    List<String[]> allRows = cSVFileReader.readAll();
    String[][] array = new String[allRows.size()][];
   for (int i = 0; i < allRows.size(); i++) {
       String[] row = allRows.get(i);
       array[i] = row;
       h = row.length;
       r++;
          }
   int[][] mResult = new int[r][h];
   for (int i =0; i<r; i++) {
      for (int j = 0; j< h; j++) {
          mResult[i][j] = Integer.parseInt(array[i][j]);
      } 
   }
   return mResult; }

means I had wrong approach. All I need was to convert List of Strings to 2d array of Strings, and next to 2d array of int

Convert List to Array int[][]

2 Answers2

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