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]