The class TicTacToe manages a 3 × 3 String Array, which is created as an empty array by the constructor.
The TicTacTo class should include the following methods:
public String toString()
Returns a String that can be printed by the caller. Useful also for displaying the state of the board before having the user enter in a new col,row for playing.
public void play(int col, int row, String symbol)
Places the indicated symbol at the specified col,row in the grid. (Note that the parameters specify the human-friendly col-row order while the actual grid is row-major and needs to be specified as grid[row][col].)
public boolean gameOver()
Checks the board to see if the game is over, either because there is a winner or because the board has been filled. Calls the checkForWinner() method to assist in making that determination.
public String checkForWinner()
Goes through the board to identify if there are any winning columns, winning rows, or winning diagonals. If there is a winner, returns the symbol (X or O) of the winner. If no one has won yet, returns a null value.