In Java, why isn't nextInt() retrieving every number from this text file?

Question

  public GameofLife(int gen)
  {
   generations = gen; 
   life = new boolean[20][20];
   try {
      Scanner pablo = new Scanner(new File("life100.txt"));
      pablo.nextInt(); //eliminate 100 (number of files in the list)
      while (pablo.hasNextInt())
          {
            life[pablo.nextInt()][pablo.nextInt()] = true;
          }
        } catch(Exception e){}
     out.print(Arrays.deepToString(life));
    }

I'm trying to read in 100 pairs int coordinates for an array from a text file, but for some reason this setup doesn't get every number; after it reads in row 3 it stops. The text file is in the setup

100
1    3
1    7
1    8
1   11
1   12
1   17
2    1
2    5
2    8
3    7
3   13
3   16
3   20
4    1
4    5
4   15
4   17

and goes all the way up to 19 18. Yet when I print it, with the out.print(Arrays.deepToString(life)); , every position after row three is false, whereas I'm setting this up so that every pair of coordinates on the text file starts as true in the matrix.

Is this a problem with my nextInt() scanner function? Or something else? And what is the best way to fix it? Please I need help. Any advice, comments, or ideas are welcome. Thank you

Answer 1

If that's the actual file content it looks like you're exceeding the bounds of your array when it reads in 3 20 There is no [3][20] allocated in life , it would only go out to [3][19] .

This is being obscured by your try/catch block which catches and drops the ArrayIndexOutOfBoundsException . As the comments suggest, printing a stack trace is a better default catch behavior than doing nothing, which would quickly reveal this error.

Try putting e.printStackTrace(); in the catch block to see what I'm talking about.

Since Java arrays are indexed starting from 0, if your file contains row+column positions going from 1 to 20, you need to subtract 1 from the value in the file before adding it to the array, eg

life[pablo.nextInt() - 1][pablo.nextInt() - 1] = true;