public void printPuzzle()
    {
        for(int i=0; i<9; i++)
        {
            for(int j=0; j<9; j++)
            {
                if(grid[i][j].getValue()==N._0)
                {
                    System.out.print(" .");
                }
                else
                {
                    System.out.print(" " + grid[i][j].getValue().intValue());
                }
            }
            System.out.println();
        }
        System.out.println();
    }