How to create a 2d grid array with information from another

Question

I'm trying to print a 2d grid with random numbers and another equally sized grid with -1s in place of the numbers that are evenly divisible by 3. I finished pretty much everything, but the second grid is only printing -1s. What am I doing wrong? How can I get the second grid to only print -1s where the numbers are evenly divisible by 3? Thanks!

public class practice

{



   public int[][] createArray(int rSize, int cSize) {

        Random r = new Random();

        int[][] array = new int[rSize][cSize];

        for (int row = 0; row < array.length; row++) {

            for (int col = 0; col < array[0].length; col++) {

                array[row][col] = r.nextInt(25);

            }

        }

        return array;

    }

    public void print2DArray(int[][] Array) {

        for (int row = 0; row < Array.length; row++) {

            for (int col = 0; col < Array[0].length; col++) {

                System.out.print(Array[row][col] + "\t");

            }

            System.out.println("\n");

        }

    }

    public int[][] createCoords(int[][] Array) {

        int[][] coord = {

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},

            {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1}

        };

        for (int row = 0; row < coord.length; row++) {

            for (int col = 0; col < coord[0].length; col++) {

                System.out.print(coord[row][col] + "\t");

            }

            System.out.println("\n");

        }

        for (int row = 0; row < coord.length; row++) {

            for (int col = 0; col < Array[row].length; col++) {

                if (Array[row][col] % 3 == 0) coord[row][col] = -1;

            }

       }

        return coord;

    }

    public static void main(String[] args) {

        Scanner in = new Scanner(System. in );

        practice c = new practice();

        int[][] myArray;



        myArray = c.createArray(10, 10);



        c.print2DArray(myArray);

        c.createCoords(myArray);

    }

}

Answer 1

It looks like you're printing the coords array before you're checking for Array elements being a multiple of 3, plus you're initializing coords to all -1 so changing an element of coords to -1 does... nothing. Initialize coords to all 0's (which is the default, so you don't need to initialize it at all, just declare it) then print it after checking Array .

A few style things: First, initial uppercase identifiers are generally reserved for classes, in fact there's already a java.lang.reflect.Array in the standard class library. Use array instead, or better yet, use a name that describes it's use , not it's type. Second, you've already got a print2DArray method, why not use it in createCoords ? Finally, coords needs to be the same size as Array (or whatever you rename it to :-) ), so you should declare it as such. If you change the size you pass to createArray , you have to remember to change coords as well.