Working with MultiDimensional arrays

Question

Hi,
Just wondering if anyone could help with a problem Im
having with multi-dimensional arrays in Java:-
I want to create a multi-dimensional array (e.g. 3 dimensions). I know this can be defined by code such as:-
int[ ][ ][ ] my_array = new int[10][10][10];
(would create a 10x10x10)
My problem is that I want to address the array with indexes that aren't known at compile time, trying to do this causes an error:-
e.g. my_array[0][0][0] = 1; is ok (i.e. the element at 0,0,0 is set to 1)
but if the indexes 0,0,0 are replaced by the return value of some function,
e.g.
my_index1 = generateIndex(x, y, .... etc);
my_index2 = generateIndex(a, b, ...etc);
my_index3 = generateIndex(f,g, .. etc);
(where generateIndex is some function that returns an integer)
and the array element set with
my_array[my_index1][my_index2][my_index3] = 3;
This generates an error. I know that this problem can be overcome through the use of pointers in C++ but since Java doesn't use pointers, im a bit stuck!
I have come across a method that overcomes this for a 1D array, using the setInt function of the Array class, e.g.
Array.setInt(my_1Darray, 0, 1); (would set the first value of my_1Darray to 1);
(i.e. Array.setInt(array_name, int index, int value);
But I can't see how this works with multidimensional arrays.
If anyone could shed any light on this problem, that would be great.
Thanks,
Peter

Answer 1

public class NDArray {
        public static void main(String[] s) {
                int[][][] _3D = new int[10][10][10];
                for (int c = 0; c < 1000; c++)
                        _3D[rnd()][rnd()][rnd()]=rnd();
                for (int i=0; i < 10; i++) {
                  for (int j=0; j < 10; j++) {
                    for (int k=0; k < 10; k++) {
                        System.out.print(_3D[i][j][k]);
                        System.out.print(" ");
                  System.out.println();
                System.out.println();
        static int rnd() {return (int) (10*Math.random());}
/* output (example):
7 0 0 4 9 9 3 0 0 2
0 1 8 9 6 0 0 0 0 0
5 3 0 5 0 0 1 0 0 3
5 6 0 5 0 0 3 0 0 0
0 0 0 0 4 0 0 5 8 6
0 9 0 9 0 1 0 2 0 0
3 3 8 6 0 0 1 0 3 4
9 6 7 0 0 0 3 6 6 3
2 0 8 7 0 1 4 0 7 0
8 0 4 4 3 0 0 5 4 0
0 0 0 0 3 0 1 0 0 4
9 0 8 9 1 0 9 0 9 0
0 8 3 4 1 0 8 0 0 2
3 0 0 7 3 3 0 5 0 0
0 0 0 1 4 6 0 0 0 3
3 5 8 5 8 0 8 2 0 4
4 0 1 7 0 1 0 4 4 0
6 0 5 0 0 4 0 8 1 0
0 0 6 6 2 0 0 4 5 0
0 6 7 0 4 0 7 5 0 0
2 4 0 5 0 0 0 2 1 7
0 6 0 9 0 0 6 1 2 0
0 5 9 0 1 2 4 0 8 6
0 0 8 0 0 3 3 8 0 0
4 7 5 9 0 8 1 0 0 9
2 0 0 3 0 0 8 3 0 7
0 6 0 6 0 0 0 0 1 0
0 9 9 8 4 2 0 0 7 2
4 0 0 9 0 0 0 1 0 6
7 0 6 5 2 3 7 8 0 2
0 0 3 5 0 0 0 0 0 0
3 0 0 0 0 2 0 0 6 0
6 0 3 3 6 0 4 0 1 6
0 0 7 2 0 8 0 0 0 0
0 0 9 0 6 8 2 1 0 0
9 0 4 1 3 9 3 2 7 7
0 3 1 0 3 0 0 9 0 5
0 0 0 0 6 0 4 8 0 5
1 8 4 6 7 0 0 4 4 0
0 4 8 0 0 0 6 0 4 0
0 9 3 0 0 0 6 0 0 8
6 8 2 9 6 0 0 7 9 0
7 1 9 0 0 5 0 2 3 0
0 0 0 0 9 9 0 7 0 9
9 8 8 2 9 8 0 5 8 0
2 3 0 4 0 4 1 0 6 9
3 3 0 0 0 0 7 6 9 3
6 2 2 1 0 5 8 3 0 6
0 6 0 0 0 0 0 0 7 5
0 6 0 0 0 3 3 0 2 0
3 6 5 5 8 2 0 9 1 0
8 0 7 0 9 0 9 0 2 0
0 2 9 0 0 1 2 4 0 2
3 1 0 2 0 0 0 0 0 0
0 5 0 3 8 8 3 0 0 0
9 0 9 0 5 1 0 9 5 0
8 0 0 8 8 7 0 3 1 0
4 0 0 0 1 8 0 9 0 5
0 0 6 6 0 0 5 2 6 8
0 4 0 9 0 0 2 0 0 3
0 5 8 1 7 0 0 4 2 0
6 5 0 0 2 0 6 8 8 7
0 0 0 0 3 0 8 4 0 0
2 3 3 0 0 7 6 8 0 4
4 1 7 3 8 0 2 3 3 0
1 5 0 0 4 1 3 7 3 1
0 0 0 6 0 6 0 0 3 0
3 7 0 4 5 9 5 5 0 8
3 8 6 4 0 0 0 1 6 0
0 0 2 0 2 9 0 0 0 5
0 5 6 0 5 5 4 0 6 7
0 2 2 0 9 7 4 2 9 0
4 0 5 4 8 3 0 0 2 0
0 0 9 3 3 0 8 8 7 0
0 7 9 7 0 0 0 7 1 0
2 0 0 0 5 8 2 0 0 5
2 4 9 6 6 0 0 0 6 0
0 6 6 7 0 2 0 0 5 2
0 9 0 4 8 5 1 0 7 6
0 0 7 0 4 0 3 8 0 9
9 4 0 0 0 4 0 0 0 5
2 0 4 7 7 5 4 0 9 0
0 0 1 0 5 0 1 0 6 0
0 6 0 9 0 9 0 4 7 0
5 9 6 6 2 8 8 4 1 4
9 7 3 2 7 6 0 2 3 0
3 1 5 0 8 0 0 0 0 0
9 0 0 3 0 8 7 0 4 0
8 6 6 4 0 4 6 4 5 0
0 0 0 0 0 4 4 0 0 9
8 8 0 2 0 0 0 1 0 0
6 2 1 1 9 0 5 1 0 0
0 9 1 0 6 0 4 0 0 0
9 4 0 3 0 1 0 7 6 0
0 9 0 7 8 6 0 5 0 0
0 8 8 9 0 5 7 0 0 0
0 4 5 1 6 0 5 2 9 3
6 0 0 0 0 0 0 9 1 0
5 9 1 9 2 5 3 0 0 9
2 9 5 1 7 0 0 0 9 0
*/Seems to work just fine. How is your code different from mine?