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Thread: Problem reading correctly from a file

  1. #1
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    Default Problem reading correctly from a file

    Hey guys, so I'm trying to read from a .txt file (which is written in a specific way) and then save some integers in a 2-dimensional array. The .txt file is written like this:

    5

    4 5 3 2 1
    1 3 2 4 5
    2 5 3 4 1
    1 4 3 2 5
    4 3 2 1 5

    My code is this:

    int[][] protimiseisA = null;
    in = new BufferedReader(new FileReader("prefsA.txt"));
    //reading the first number
    String str = in.readLine();
    //saving it for use later
    int sum = Integer.parseInt(str);
    //reading the empty line and discarding it
    str = in.readLine();
    //gist of the code, read the next five lines and save the integers in the array
    for (int x = 0; x < sum; x++) {
        str = in.readLine();                
        String[] str2 = str.split("\\s+");
            for (int y = 0; y < sum; y++) {
                 protimiseisA[x][y] = Integer.parseInt(str2[y]);
             }
     }

    Of course that's only part of the code but that's where the problem is imo, since it throws a NullPointerException at the line "protimiseisA[x][y] = Integer.parseInt(str2[y]);"

    Any help would be greatly appreciated!


  2. #2
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    Default Re: Problem reading correctly from a file

    So where did you initialize protimiseisA ?

  3. #3
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    Default Re: Problem reading correctly from a file

    Hm, nowhere. I thought I did initialize it with this line: "int[][] protimiseisA = null;" Should I fill the array with zeros first? Sorry, I'm kinda new to programming...

  4. #4
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    Default Re: Problem reading correctly from a file

    "int[][] protimiseisA = null;" say the variable protimiseisA is an int[][] type. But assigning anything to null means no memory location has been assigned to the variable, Thus making java throw the nullPointerException. To initialize an array of arrays you will want to use "new insertTypeHere[insertSizeHere][]", if you know the second dimension, put it in, otherwise i think you may need to initialize the inner array. I say I think because its been a while, and I currently don't have a jdk installed on this computer.

  5. The Following User Says Thank You to JJeng For This Useful Post:

    stavrakas (April 6th, 2011)

  6. #5
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    Default Re: Problem reading correctly from a file

    Wow, thx so much, I can't believe I missed that... Now time to work on the rest of the code

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