java - Filling a 2d array with numbers in a rhombus form

Question

I need some help filling a 2D array using a nested for loop. The desired output is this...

20.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0
19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0
18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0
17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0
16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0
15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0
14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0
13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0
11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0
10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0
12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0
13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0
15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0
16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0
17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0
18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0
19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0
20.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0

This is my code to fill the array...

int row;
int column;
int counter = 10;
int counter1 = 10;
for (row = 0; row < array.length; row++) {
    array[row][0] = obj.getZ(10, counter);
    counter--;
    for (column = 0; column < array[row].length; column++) {
        array[row][column] = obj.getZ(counter1, 10);
        counter1--;

I already declared the array to be 20 by 20 and obj.getZ is just simply calling this method...

public double getZ(double x, double y) {
    double z = (Math.abs(x) + Math.abs(y));
    return z;

The array is the z value which is formed by the absolute values of x and y.

Answer 1

Not the best solution, but it should solve the issue:

import java.util.Arrays;

class Scratch {
    public static void main(String[] args) {
        int[][] arr = new int[21][21];
        int row = 20;
        int column = 0;
        for (int i = 0; i < 21; i++) {
            column = row;
            for (int j = 0; j < 21; j++) {
                arr[i][j] = column;
                if (j < 10) {
                    column = column - 1;
                } else {
                    column = column + 1;
                }
            }
            if (i < 10) {
                row = row - 1;
            } else {
                row = row + 1;
            }
        }
        for (int[] arrRow : arr) {
            System.out.println(Arrays.toString(arrRow));
        }
    }
}

And result is:

[20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
[19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
[18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18]
[17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]
[16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
[15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
[13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
[12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
[11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
[10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
[12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
[13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
[14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
[15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
[17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]
[18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18]
[19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
[20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]