sudoku using recursive method in java

1class Sudoku
2{
3    private int[][] sudoku;
4    private static final int UNASSIGNED = 0;
5      
6    public Sudoku()
7    {
8        sudoku = new int[9][9];
9    }
10      
11    public Sudoku(int sudoku[][])
12    {
13        this.sudoku= sudoku;
14    }
15      
16    //TO-DO Methods
17    //private boolean containsInRow(int row,int number){...}
18    //private boolean containsInCol(int col,int number){...}
19    //private boolean containsInBox(int row, int col,int number){...}
20    //private boolean isAllowed(int row, int col,int number){...}
21    //public void displaySudoku(){...}
22    //public boolean solveSudoku(){...}
23}
24