Read from File, Load arrays

Question

I'm trying to implement Banker's Algorithm in Java, but I'm having trouble loading my arrays. Here is the code I'm working with

public static void main(String[] args) throws FileNotFoundException {
    String filename = null;
    int need[][];
    int allocate[][];
    int max[][];
    int available[][];
    int n = 0;
    int m = 0;
    int lineCount = 0;
    Scanner in = new Scanner(System.in);

    System.out.println("Enter the file name.");
    filename = in.nextLine();

    File textFile = new File(filename);
    Scanner input = new Scanner(textFile);

    max = new int[n][m];
    allocate = new int[n][m];
    need = new int[n][m];
    available = new int[1][m];

    n = input.nextInt();
    m = input.nextInt();
    System.out.print("Number of Processes: " + n);
    System.out.print("\nNumber of Processes: " + m);

    max = new int[n][m];
    allocate = new int[n][m];
    need = new int[n][m];
    available = new int[1][m];

    String line = input.nextLine();

    while (line != null && lineCount < n) {

        String[] temp = line.split(" ");
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                allocate[i][j] = Integer.parseInt(line);
                System.out.println("here");
            }
            line = input.nextLine();
            lineCount++;
        }
    }
}

My sample file contains this data.

5

4

0 0 1 2 1 0 0 0 1 3 5 4 0 6 3 2 0 0 1 4

0 0 1 2 1 7 5 0 2 3 5 6 0 6 5 2 0 6 5 6

1 5 2 0

1:0 4 2 0

So, I've had a number of different errors while trying to do this. Right now I'm getting an NumberFormatException: For input string "" error. Any help is much appreciated.

Could you explain the format of the input file? It seems not consistent (e.g., a colon in the last row only). Also, could you explain what `n` and `m` is, as well as the intuition of your codes? — Tsung-Ting Kuo, Dec 01 '15 at 00:50
it would be helpful if you could post the stack trace of the ArrayIndexOutOfBoundsException and say which line number the exception is pointing to — Andy Guibert, Dec 01 '15 at 00:52

Andy Guibert · Answer 1 · 2015-12-01T01:06:14.573

0

You have a bunch of really small arrays, and you never increase the sizes of them:

int n = 0;
int m = 0;
...
max = new int[n][m];       // 0x0 array, unused
allocate = new int[n][m];  // 0x0 array, likely the culprit
need = new int[n][m];      // 0x0 array, unused
available = new int[1][m]; // 1x0 array, unused

Of these arrays, only allocate is used, and you are using it later in a for loop:

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            // OutOfBounds is probably here:
            allocate[i][j] = Integer.parseInt(line);
            System.out.println("here");
        }
        line = input.nextLine();
        lineCount++;
    }

Also, you are running Integer.parseInt(line) which is attempting to parse the whole line. You should just parse a single token at a time which would be Integer.parseInt(temp[someindex]).

edited Dec 01 '15 at 01:06

answered Dec 01 '15 at 00:55

Andy Guibert

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you're right of course. So I moved the assignment statements after n and m get their values and now I'm getting a NumberFormatException. The file has blank lines in it. – jynx678 Dec 01 '15 at 00:57
ok, so now you just need to do a bit of debugging -- start by printing out each line in your for loop, so you know which line the issue is on. Instead of printing out "here", try printing out `line` instead. The numberFormatException is probably on the last line where you have `1:0` – Andy Guibert Dec 01 '15 at 00:59
I changed the txt file (deleted 1:0) and I get the same error. I tried printing out LINE in the loop, same error. I moved it outside the loop, same error. It says For input string: "" – jynx678 Dec 01 '15 at 01:08
Does it have something to do with the spaces between the numbers in the file? – jynx678 Dec 01 '15 at 01:10
It's ok that there are spaces. You are doing `String[] temp = line.split(" ")` which splits a String up at each space. So if you have the String `"1 2 3 4"` and do split(" ") on it, you will get an array {"1", "2", "3", "4"} – Andy Guibert Dec 01 '15 at 01:12
Is it the `parseInt` that is throwing the exception? – jynx678 Dec 01 '15 at 01:17
@StephaniePrecht you should really make separate questions instead of updating your original post with the new issues -- now the original answer I gave no longer answers the question since it has been edited with a different problem – Andy Guibert Dec 01 '15 at 14:07
Sorry! won't do it again. Thanks for your help. – jynx678 Dec 02 '15 at 00:49

Read from File, Load arrays

1 Answers1