Tic Tac Toe

package tictactoe;

/**
 *
 * @author Monty
 */
public class TicTacToe {

    public static void main(String[] args) {
            TTT TTTGame = new TTT();

            TTTGame.play();
    }
}

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package tictactoe;

import java.util.Scanner;


public class TTT {
    private String[][] tttBoard;
    private String player1, player2;


    /**
     * constructor
     * pre: none
     * post: tttBoard has been initialized. player1 is X and player2 is O.
     */
    public TTT() {
        player1 = "X";
        player2 = "O";
        tttBoard = new String[3][3];
        for(int row = 0; row < tttBoard.length; row++) {
            for (int col = 0; col < tttBoard[0].length; col++) {
                tttBoard[row][col] = " ";
            }
        }
    }


    /**
     * Plays a game of tic-tac-toe with two users, keeping track
     * of player (X or O) turns. player1 goes first.
     * pre: none
     * post: A game of tic-tac-toe has been played.
     */
    public void play() {
        String currPlayer = player1;
        int movesMade = 0;

        do {
            displayBoard();
            makeMove(currPlayer);
            movesMade += 1;
            if (currPlayer == player1){
                currPlayer = player2;
            } else {
                currPlayer = player1;
            }
        } while (movesMade <= 9 && winner() == " ");
        displayBoard();
        System.out.println("Winner is " + winner());
    }


    /**
     * Displays the board.
     * pre: none
     * post: The tic-tac-toe board has been displayed.
     */
    private void displayBoard() {
        for(int row = 0; row < tttBoard.length; row++) {
            for (int col = 0; col < tttBoard[0].length; col++) {
                System.out.print("[" + tttBoard[row][col] + "]");
            }
            System.out.println();
        }
    }


    /**
     * Prompt user for a move until a valid move has been made.
     * pre: none
     * post: A mark has been made in an empty tic-tac-toe board square.
     */
    private void makeMove(String player) {
        Scanner input = new Scanner(System.in);
        boolean validMove = false;
        int row, col;

        do {
            System.out.print("Player " + player + ", Enter row number (0, 1, 2): ");
            row = input.nextInt();
            System.out.print("Player " + player + ", Enter column number (0, 1, 2): ");
            col = input.nextInt();
            if ((row >= 0 && row < tttBoard.length &&
                col >= 0 && col < tttBoard[0].length) &&
                tttBoard[row][col].equals(" ")) {
                tttBoard[row][col] = player;
                validMove = true;
                } else {
                    System.out.println("Invalid move.  Try again.");
                }
        } while (!validMove);
    }


    /**
     * Determine winner. Return " " if no winner.
     * pre: none
     * post: X, O, or " " has been returned as the winner.
     */
    private String winner() {

        /* test rows */
        for (int row = 0; row < tttBoard.length; row++) {
            if (tttBoard[row][0].equals(tttBoard[row][1]) && tttBoard[row][1].equals(tttBoard[row][2]) &&
                !(tttBoard[row][0].equals(" "))) {
                    return(tttBoard[row][0]);
            }
        }

        /* test columns */
        for (int col = 0; col < tttBoard[0].length; col++) {
            if (tttBoard[0][col].equals(tttBoard[1][col]) && tttBoard[1][col].equals(tttBoard[2][col]) &&
                !(tttBoard[0][col].equals(" "))) {
                    return(tttBoard[0][col]);
            }
        }

        /* test diagonal */
        if (tttBoard[0][0].equals(tttBoard[1][1]) && tttBoard[1][1].equals(tttBoard[2][2]) &&
            !(tttBoard[0][0].equals(" "))) {
            return(tttBoard[0][0]);
        }

        /* test other diagonal */
        if (tttBoard[0][2].equals(tttBoard[1][1]) && tttBoard[1][1].equals(tttBoard[2][0]) &&
            !(tttBoard[0][2].equals(" "))) {
            return(tttBoard[0][2]);
        }

        return(" ");
    }
}