NullPointerException while trying to initialize a 2d array

Question

I am getting a nullPointerException trying to add values from a text file to a 2d array. The first 2 values determine the rows and columns. Any ideas what is throwing it. Ignore the exception handling, and the print statements. I am trying to get the array initialized then will go back and beef it up a bit.

public Help(String filename) throws FileNotFoundException,
        InvalidFileFormatException {
    this.filename = filename;

    System.out.println("Reading in file: " + filename);

    String number = "";
    int row = 0;
    int col = 0;
    int count = 0;

    try {
        Scanner inputFile = new Scanner(new File(filename));

        while (inputFile.hasNextInt()) {
            row = Integer.parseInt(inputFile.next());
            col = Integer.parseInt(inputFile.next());
            System.out.println("Row : " + row);
            System.out.println("Col : " + col);
            baseMap = new double[row][col];
            System.out.println(baseMap[2][4]);
            for (int i = 0; i < baseMap.length; i++){
                for (int j = 0; j < baseMap[i].length; j++){
                    baseMap[i][j] = Double.parseDouble(inputFile.next());
                }
            }
        }
System.out.println(baseMap[2][4]);
    } catch (Exception e) {
        System.out.println(e.toString());
    }

OUTPUT Reading in file: sampleMap2.txt Row : 5 Col : 5 0.0 Exception in thread "main" java.lang.NullPointerException

For starters, use Scanner#nextInt instead of calling Integer#parseInt yourself; it's more readable, and you'll get a more informative exception if it fails. — chrylis -cautiouslyoptimistic-
– chrylis -cautiouslyoptimistic-, Commented Sep 9, 2013 at 8:29

Scary Wombat · Accepted Answer · 2013-09-09 07:59:00Z

2

What value do you expect to see here;

baseMap = new double[row][col];
System.out.println(baseMap[2][4]);

How about if row == 1?

Also what if there is no more data at:

baseMap[i][j] = Double.parseDouble(inputFile.next());

Maybe you just don't have enough data.

answered Sep 9, 2013 at 7:59

Scary Wombat

44.9k6 gold badges38 silver badges67 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

user2541019 Over a year ago

I was just seeing if it actually initialized a 0.0 at that position. It prints out 0.0 before throwing the exception.

Scary Wombat Over a year ago

so what line is throwing the exception?

user2541019 Over a year ago

It was a different method in a different class that was throwing the exception. I am terribly sorry for wasting your time, but do appreciate your help. It got me thinking and helped me find the fix.

Collectives™ on Stack Overflow

NullPointerException while trying to initialize a 2d array

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related