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Thread: 1st time using methods

  1. #1
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    Default 1st time using methods

        public static int loadMat(int [][] mat) throws Exception{
            int size, row, col = 0, num;
            Scanner input = new Scanner(System.in);
                System.out.print("Enter the size of the square : ");
                    size = input.nextInt();
                    mat = new int [size][size];
    System.out.println();
    System.out.println("Enter the value for");
        for (row = 0 ; row < size ; row++){
            for (col = 0 ; col < size ; col++){
                System.out.print("ROW " + row +" COL " +col +" : ");
                    num = input.nextInt();
                    mat[row][col] = num;
        }
    }
    return size;
        }
     
    public static void printMat(int [][] mat, int size){
         for (int i = 0 ; i < size ; i++){
             System.out.print("ROW " + i +" ");
                     for (int j = 0 ;j < size; j++){
                         System.out.print(size);
                     }
         }
     }
     
     
     
    public static void main(String[] args) throws Exception{
    int [][] themat = new int [10][10];
    int thesize;
    int magicnum;
    boolean row,col,diag;
    thesize = loadMat(themat);
    printMat(themat, thesize);
     
    }
    }

    so far i have that done...
    which prompts the user to fill in the matrix... what i dont get is in the method printMat
    how can i get a hold of the numbers the user just entered for the matrix?


  2. #2
    Super Moderator copeg's Avatar
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    Default Re: 1st time using methods

    how can i get a hold of the numbers the user just entered for the matrix?
    You've passed the array as a parameter, so just loop through the array by row/colum
    for ( int i = 0; i < mat.length; i++ ){
        for ( int j = 0; j < mat[i].length; j++ ){
          //do something with mat[i][j]
        }
    }

  3. #3
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    Default Re: 1st time using methods

    i already tried that code

     public static void printMat(int [][] mat, int size){
        for ( int i = 0; i < mat.length; i++ ){
        for ( int j = 0; j < mat[i].length; j++ ){
         System.out.println(mat[i][j]);
        }
    }
     }

    but the value of mat[i][j] is 0 which never changed even if the user inputed diff. values.. heres my whole code
    still dont know how to access the inputted values.


       public static int loadMat(int [][] mat) throws Exception{
            int size, row, col = 0, num;
            Scanner input = new Scanner(System.in);
                System.out.print("Enter the size of the square : ");
                    size = input.nextInt();
                    mat = new int [size][size];
    System.out.println();
    System.out.println("Enter the value for");
        for (row = 0 ; row < size ; row++){
            for (col = 0 ; col < size ; col++){
                System.out.print("ROW " + row +" COL " +col +" : ");
                    num = input.nextInt();
                    mat[row][col] = num;
        }
    }
    return size;
        }
     
     
     public static void printMat(int [][] mat, int size){
        for ( int i = 0; i < mat.length; i++ ){
        for ( int j = 0; j < mat.length; j++ ){
         System.out.println(mat[i][j]);
        }
    }
     }
     
     
     
    public static void main(String[] args) throws Exception{
    int [][] themat = new int [10][10];
    int thesize;
    int magicnum;
    boolean row,col,diag;
    thesize = loadMat(themat);
    printMat(themat, thesize);
     
    }
    }

  4. #4
    Super Moderator copeg's Avatar
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    Default Re: 1st time using methods

    Didn't spot this earlier (obviously), but you re-assign the variable mat in the load method, once the load method exits that variable is out of scope (and the parameter unchanged - pass by value ). I'd recommend returning the array from the load method, then send that into the print method. Lastly, take a look at the print method because it doesn't fully implement my suggestion above.

  5. #5
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    Default Re: 1st time using methods

    yeah but my homework specifically said that the data should be stored in the reference variable called mat and the size of the method should be the value returned

    uhh you said to return the array in the load method but as far as i know you can only return one value i think

  6. #6
    Super Moderator copeg's Avatar
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    Default Re: 1st time using methods

    Well technically the size is returned with the array (via the length property). But regardless, you cannot recreate the reference to the array in the method and hope that change takes effect outside of the method. Return the array, create an object which contains the array as an instance variable and pass that through the functions, or create 2 functions, one which asks for the size, create the array using that value, and pass that created array to another function that fills in the array.

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