Enumeration that stores the symbols of the cells

This is a class which stores a list of constants. These constants are
used to display the contents of the cell and the player's symbol.
Enumeration that has all the game states

This class stores the list of constants that describes the current state
of the game.
This class contains the game playing world

This class contains the world in which the game is played. It handles
the state of the game as well as the grid on which tic-tac-toe is
played.
The grid on which tic-tac-toe is played

This class represents the grid on which the game is played. The Xs andOs
are drawn on this grid.
The cells on the grid on which move is made

This class contains the cells on which the player can make his move.
This move will be drawn on the cell which will be placed on the grid.
The class which runs the game

This is the main class which has the main method and runs the game.