//assume the grid is of size n x n
//assume at location x,y
for(int i = -1; i <= 1; i++){
    for(int j = -1; j <= 1; j++){
        if(i==0 && j==0)
            continue;

        if(x+i > 0 && x+i <= n && y+j > 0 && y+j <= n){
            //you can safely check square x+i, y+j
        }

        else
            //probably do nothing, so omit this statement...

    }
}