Game of Life ArrayIndexOutofBounds

Question

I\'m doing the Conway\'s game of life. I\'m pretty sure I\'m close to finished, but when I run it, I get Exception in thread \"main\" java.lang.ArrayIndexOutOfBoundsExcep

Answer 1

When r is 0, this one is not valid: old[r - 1][c].
Thus you get the exception you posted.

I suggest you simplify it like this.

    boolean isValidPosition(int r, int c){
        return 
            0 <= r && r < N &&
            0 <= c && c < M;

    }

    int getNeighboursCount(boolean[][] old, int r, int c){
        int neighbors = 0;
        for (int i=-1; i<=1; i++){
            for (int j=-1; j<=1; j++){
                if (i!=0 || j!=0){
                    if (isValidPosition(r + i, c + j)){
                        if(old[r + i][c + j])
                        {
                            neighbors++;
                        }
                    }
                }
            }
        }
        return neighbors;
    }