How to add arrays to ArrayList?

Question

I have an int[3][3] array and it contains only 0 or 1 values, if the value is 1 I want to add the coordinates of this value in the ArrayList as int[2] array, but I don\'t know w

Answer 1

You need to create a new coordinate object every time you add it:

if (board[i][j] == 1) {
  int[] coordinate = new int[2];
  coordinate[0] = i;
  coordinate[1] = j;
  arrayList.add(coordinate);
}

or shorter:

if (board[i][j] == 1) {
    arrayList.add(new int[]{i, j} );
}

Otherwise you will add the same object multiple times and modify it each time so only the last coordinate remains.

If you make it a habit to use narrow scoped (temporary) variables, this typically comes naturally as you do not drag state around outside of loops.