SudokuField which represent value of each field on the board
Nothing important
Changes performed in order to support SudokuField.
A class which stores values of some field on the board.
changed performed in order to use Sudokufield
This class implements Printer. Its only purpose is to show game's board.
Created Printer interface which contain method show(). This is better
approach to printing a board.
Changes required to run GUI.
Implementing GUI:

-Used GriBagLayout
-Yeach field is represented as JLabel
Now main class use GUI
Moved Dao from package Board to package Dao
Implement cloneable and comparable
Nothing important
Implementing serialization