Problems with returning an array

Question

I have a 2D int[][] and am trying to write a function that locates a 0 in that array and returns an array with its coordinates.

I came up with this:

public int[] locateZero(int[][] array) {
    int[] coordinates = new int[2];
    for (int i=0; i < array.length; i++) {
        for (int j=0; j < array[0].length; j++) {
            if (array[i][j] == 0) {
                //The following line doesn't work!
                coordinates.add(i, j);
            }
        }
    }
    return coordinates;
}

NetBeans keeps underlying the add method, stating that it cannot find it.

Could someone help me, please?

It's a stupid problem, I know. I'm a Java noob.

Your IDE is flagging it but does it still work when you run or are you getting an error? — Chris Farr
– Chris Farr, Commented Apr 21, 2018 at 15:18
coordinates is not a list there are no way to use coordinates.add(i, j); with array — Youcef LAIDANI
– Youcef LAIDANI, Commented Apr 21, 2018 at 15:19
I think you want to do this coordtinates[0] = i; and coordtinates[1] = j; — Shafin Mahmud
– Shafin Mahmud, Commented Apr 21, 2018 at 15:23

Ian Rehwinkel · Accepted Answer · 2018-04-21 15:21:48Z

4

Your array named coordinates is an array. Arrays do not support an add() function. If you want to have an add function, use ArrayList<Integer> instead.

What would be more typical though, would be to assign the values to your array like so:

public int[] locateZero(int[][] array) {
    int[] coordinates = new int[2];
    for (int i=0; i < array.length; i++) {
        for (int j=0; j < array[0].length; j++) {
            if (array[i][j] == 0) {
                //here is the difference
                coordinates[0] = i;
                coordinates[1] = j;
            }
        }
    }
    return coordinates;
}

edited Apr 21, 2018 at 15:21

answered Apr 21, 2018 at 15:19

Ian Rehwinkel

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Comments

Constantin Müller · Accepted Answer · 2018-04-21 15:26:40Z

As already said you can't use add. Arrays don't support this. But I won't use an array to return the coordinates. I would write a simple class to store them.

class Coordinate
{
    public int coordX;
    public int coordY;

    Coordinate(int x, int y)
    {
        this.coordX = x;
        this.coordY = y;
    }
}

private Coordinate locateZero(int [][] array)
{
    if(array == null)
    {
        return null;
    }

    for(int x = 0; x < array.length; x++)
    {
        for(int y = 0; y < array[0].length; y++)
        {
            if(array[x][y] == 0)
            {
                return new Coordinate(x, y);
            }
        }
    }

    return null; // Value zero not found in array
}

// Usage of Coordinate class

Coordinate coords = locateZero(myArray);

if(null != coords)
{
    // Value zero found print coordinates
    System.out.println(coords.coordX);
    System.out.println(coords.coordY);
}

Manish Bansal · Accepted Answer · 2018-04-21 15:50:42Z

1

You are having many errors in this program. First of all you are using a array not ArrayList. There is no 'add' method in array in java. Second you want to return 2 values i.e. coordinates then you can simply make a 2D array and return it. So your function will look like this.

public int[][] locateZero(int[][] array) {
    int[][] coordinates = new int[1][1];
    for (int i=0; i < array.length; i++) {
        for (int j=0; j < array[0].length; j++) {
            if (array[i][j] == 0) {
                coordinates[0][0]=i;
                coordinates[0][1]=j;
                break;
            }
        }
    }
    return coordinates;
}

answered Apr 21, 2018 at 15:50

Manish Bansal

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