Question

I have String array like this one:

String[][][][][] map = new String[9][13][2][1][1];

and when I’m trying update one fild, like this:

map[0][0][1][0][1]  = "true";

every fild is updating to “true”, this one:

map[0][1][1][0][1]

this one:

map[0][2][1][0][1]

why this is happening?

this is my code:

int UP          = 0;
int UP_RIGHT    = 1;
int RIGHT       = 2;
int DOWN_RIGHT  = 3;
int DOWN        = 4;
int DOWN_LEFT   = 5;
int LEFT        = 6;
int LEFT_UP     = 7;

String[][][][][] map = new String[9][13][2][1][1];

public PitchMoveHelper() {
    String[][] move = {
            {String.valueOf(UP), "false"},
            {String.valueOf(UP_RIGHT), "false"},
            {String.valueOf(RIGHT), "false"},
            {String.valueOf(DOWN_RIGHT), "false"},
            {String.valueOf(DOWN), "false"},
            {String.valueOf(DOWN_LEFT), "false"},
            {String.valueOf(LEFT), "false"},
            {String.valueOf(LEFT_UP), "false"}
        };

    String[][] used = {{"used", "false"}};

    for(int z = 0; z < 9; z++) {
        for(int x = 0; x < 13; x++) {
            map[z][x][0] = used;
            map[z][x][1] = move;
        }
    }

    //this.updateLeftBand();
    //this.updateRightBand();
    //this.updateTopBand();
    //this.updateBottomBand();

    map[0][0][1][0][1]  = "true"; 

    System.out.println(Arrays.deepToString(getPitchMap()));
}

Answer 1

Your immediate problem is that the String array stores references, not actual strings. When you say

map[z][x][0] = used;
map[z][x][1] = move;

There is a single instance of used being referenced by ALL elements [z][x][0] of map (and the same for move and [z][x][1]. Any change indexed by the 4th of 5th subscript is changing that single instance, affecting what is seen by all subscripts.

To clarify more, all the following entries in map point to the same instance:

map[0][0][0]
map[0][1][0]
       .
       .
map[0][12][0]
map[1][0][0]
  etc.

To solve the problem you need to make a deep copy of used and move for every assignment in the loop:

for(int z = 0; z < 9; z++) {
    for(int x = 0; x < 13; x++) {
        map[z][x][0] = deepCopy(used);
        map[z][x][1] = deepCopy(move);
    }
}

Where deepCopy() makes a complete copy of the input array.

String[][] deepCopy(String [][] arr)
{
    String[][] temp = new String[arr.length][];
    for (int i=0; i<arr.length; i++)
    {
         temp[i] = new String[arr[i].length];
         for (int j=0; j<arr[i].length; j++)
             temp[i][j] = arr[i][j];
    }
    return temp;
}