Question

I think I have the code correct for storing data in an ArrayList. However, I can’t convert the list to a String[][]. Here’s my code:

        int row = 0;
        int col = 0;

        String fileInput = JOptionPane.showInputDialog(null, 
                "Please enter the path of the CSV file to read:");

        File file = new File(fileInput);

        BufferedReader bufRdr;
        bufRdr = new BufferedReader(new FileReader(file));
        String line = null;

        // Construct a new empty ArrayList for type String
        ArrayList<String[]> al = new ArrayList<String[]>();

        //read each line of text file
        while((line = bufRdr.readLine()) != null) {
            String[] columnData = line.split(",");
            al.add(columnData);
        }

        // Convert ArrayList to String array
        String[][] numbers = (String[][]) al.toArray(new String[al.size()][16]);

I’m getting an error stating I can’t convert to a String[][] type. Any ideas on what I can do?

EDIT: So the conversion problem is solved (the edited code is pasted above) – now its outputting nothing though. I feel like I must have stored the data incorrectly. What should I add/change?

Answer 1

The array will be an Object[] of String[], so the cast doesn’t work. You can (and should) use the toArray() version that supplies the array to populate:

String[][] numbers = (String[][]) al.toArray(new String[al.size()][]);