Tic-Tac-Toe Game (Java)

Question

This program runs the game tic-tac-toe within the console. The players, X and O, take turns placing their character onto the 3x3 grid. When a player successfully makes 3 in a row, either vertically, horizontally, or diagonally, they win. If no winner is decided upon all squares being filled, it is a stalemate.

I'm wondering how efficient this code is. Are there any redundancies, formatting issues, legibility issues, etc.?

TicTacToe.java

package tictactoe;

public class TicTacToe {

    public static void main(String[] args) {
        GameBoard myGame = new GameBoard();
        myGame.displayBoard();

        int counter = 1;

        while (myGame.gameActive() && counter < 10) {
            if (counter % 2 == 0)
                myGame.askPlayer('O');
            else
                myGame.askPlayer('X');
            counter++;

            System.out.println("\n");
            myGame.displayBoard();
            myGame.checkForWinner();

            if (counter == 10 && myGame.gameOnGoing() == true)
                System.out.print("Stalemate!\n");
        }

    }

}

GameBoard.java

package tictactoe;

import java.util.Arrays;
import java.util.Scanner;

public class GameBoard {
    private char[][] gameBoard;
    private boolean gameOnGoing = true;

    //This is the constructor for the GameBoard class.
    public GameBoard() {
        gameBoard = new char[3][3];

        for (int row=0; row < gameBoard.length; row++) {
            Arrays.fill(gameBoard[row], ' ');
        }
    }   //end of constructor


    //This method will display the gameBoard to the screen.
    public void displayBoard() {
        for (int row=0; row < gameBoard.length; row++) {
            for (int col=0; col < gameBoard[0].length; col++) {
                System.out.print("\t" + gameBoard[row][col]);
                if (col == 0 || col == 1)
                    System.out.print("|");
            }
            if (row == 0 || row == 1)
                System.out.print("\n----------------------------\n");
        }
        System.out.println();
    }   //end of method displayBoard

    //This method will return true if the game is still active.
    public boolean gameActive() {
        return gameOnGoing;
    } //end of method gameActive

    //This method will ask the user to pick a row and column, validate
    //the inputs, and call the method makeMove().
    public void askPlayer(char player) {
        Scanner keyboard = new Scanner(System.in);
        int row, col;
        do {
            System.out.printf("Player %s, please enter a row (1-3): ",player);
            row = keyboard.nextInt();

            System.out.printf("Player %s, please enter a column (1-3): ",player);
            col = keyboard.nextInt();
        }   
            while (notValid(row,col));

        makeMove(player,row-1,col-1);

    }   //end of askPlayer method

    //This method will check to see if there are 3 x's or o's in a row
    //and return true if there is a winner, false otherwise
    public void checkForWinner() {
        //loop over each row and check for a winner
        for (int row =0; row < gameBoard.length; row++) {
            if (gameBoard[row][0] == gameBoard[row][1] && gameBoard[row][1] == gameBoard[row][2]
                    && gameBoard[row][0] != ' ') {
                System.out.print("The winner is " + gameBoard[row][0] + "!");
                gameOnGoing = false;
            }

        }

        //loop over each column and check for a winner
        for (int col=0; col < gameBoard[0].length; col++) {
            if (gameBoard[0][col] == gameBoard[1][col] && gameBoard[1][col] == gameBoard[2][col]
                    && gameBoard[0][col] != ' ') {
                System.out.print("The winner is " + gameBoard[0][col] + "!");
                gameOnGoing = false;
            }

        }

        //check the diagonals
        if (gameBoard[0][0] == gameBoard[1][1] && gameBoard[1][1] == gameBoard[2][2]
                && gameBoard[0][0] != ' ') {
            System.out.print("The winner is " + gameBoard[0][0] + "!");
            gameOnGoing = false;
        }

        if (gameBoard[2][0] == gameBoard[1][1] && gameBoard[1][1] == gameBoard[0][2]
                && gameBoard[2][0] != ' ') {
            System.out.print("The winner is " + gameBoard[2][0] + "!");
            gameOnGoing = false;
        }
    }

    //Same as above, but does not print winner or change state of gameOnGoing.
    public boolean gameOnGoing() {
        //loop over each row and check for a winner
        for (int row =0; row < gameBoard.length; row++) {
            if (gameBoard[row][0] == gameBoard[row][1] && gameBoard[row][1] == gameBoard[row][2]
                    && gameBoard[row][0] != ' ') {
                return false;
            }

        }

        //loop over each column and check for a winner
        for (int col=0; col < gameBoard[0].length; col++) {
            if (gameBoard[0][col] == gameBoard[1][col] && gameBoard[1][col] == gameBoard[2][col]
                    && gameBoard[0][col] != ' ') {
                return false;
            }

        }

        //check the diagonals
        if (gameBoard[0][0] == gameBoard[1][1] && gameBoard[1][1] == gameBoard[2][2]
                && gameBoard[0][0] != ' ') {
            return false;
        }

        if (gameBoard[2][0] == gameBoard[1][1] && gameBoard[1][1] == gameBoard[0][2]
                && gameBoard[2][0] != ' ') {
            return false;
        }
        return true;
    }   //end of method gameOnGoing

    //This method will validate if the row and column are between 1-3
    //and if the position is currently empty.
    public boolean notValid(int row, int col) {
        if (row > 3 || row < 1 || col > 3 || col < 1 || !isEmpty(row, col))
            return true;
        else    
            return false;
    } //end of method notValid

    //This method will check if a position is empty and return true
    //if the position is empty, false otherwise
    public boolean isEmpty(int row, int col) {
        if (gameBoard[row-1][col-1] == ' ')
            return true;
        else {
            System.out.print("That position is taken.\n");
            return false;
        }
    }

    //This method will validate if a player's move is allowed and return true
    //if the move was completed
    public boolean makeMove(char player, int row, int col) {
        if (row >=0 && row <=2 && col >=0 && col <=2) {
            if (gameBoard[row][col] != ' ')
                return false;
            else {
                gameBoard[row][col] = player;
                return true;
            }
        }
        else
            return false;
    }   //end of method makeMove

}

Answer 1

Below are just some quick points. I didn't get into the meat of the GameBoard class.

TicTacToe.java

• You're using a Magic Number here for your counter. This should be extracted as a constant.

• The stalemate conditional can be placed outside of the while block, as you already know that counter = 10.

• I would also extract the X and O chars as constants. I'm curious about what will happen when an unexpected char is passed to askPlayer.

• There's rarely a point in having a \n in a print or println statement. In your finaly line, you can just have `System.out.println("Stalemate!");

• You have all this game logic in a main method, when it should properly encapsulated into its own separate method.

GameBoard.java

• Minor point, but I wouldn't initialize gameOnGoing to true by default. Rather, I'd have it set after everything was initialized in the constructor.

• Extract the gameboard size, 3 as a constant.

• Regarding comments, you should use proper JavaDoc comments for your methods, and there's no need to comment the end of every method. So this,

  //This is the constructor for the GameBoard class.
  public GameBoard() {
      gameBoard = new char[3][3];
      for (int row=0; row < gameBoard.length; row++) {
         Arrays.fill(gameBoard[row], ' ');
     }
   }   //end of constructor
  

  should be this:

  /**
   * This is the constructor for the GameBoard class.
   */
  public GameBoard() {
      gameBoard = new char[3][3];
  
      for (int row=0; row < gameBoard.length; row++) {
          Arrays.fill(gameBoard[row], ' ');
      }
  }