GFG Day 7: Mini Project: Tic-Tac-Toe Game in Java

• Tic-Tac-Toe is a simple, classic two-player game, often used as an introductory project in Java programming. The game is played on a 3x3 grid where two players take turns marking the cells with X and O. The objective is to get three of your symbols in a horizontal, vertical, or diagonal row.

Rules of the Tic-Tac-Toe Game

Basic Gameplay Sequence

• The game starts with an empty board.

• Player 1 (X) chooses a cell to place their symbol.

• Player 2 (O) chooses a cell.

• Players alternate turns.

• After each move, check if the player has completed a row, column, or diagonal.

• If there is a winner, declare them; if the grid is full without a winner, declare a draw.

• The game ends.

Game Board Layout

• The game board layout will look something like this and game will begin.

      |---|---|---|        
      | 1 | 2 | 3 |
      |-----------|
      | 4 | 5 | 6 |
      |-----------|
      | 7 | 8 | 9 |
      |---|---|---|

Project Implementation

 // Tic-Tac-Toe Game
// File name: TicTacToeGame.java
import java.util.*;

public class TicTacToeGame {

    static String[] board;
    static String turn;

    // CheckWinner method will 
    // decide the combination 
    // of three box given below.
    static String checkWinner()
    {
        for (int a = 0; a < 8; a++) {
            String line = null;

            switch (a) {
            case 0:
                line = board[0] + board[1] + board[2];
                break;
            case 1:
                line = board[3] + board[4] + board[5];
                break;
            case 2:
                line = board[6] + board[7] + board[8];
                break;
            case 3:
                line = board[0] + board[3] + board[6];
                break;
            case 4:
                line = board[1] + board[4] + board[7];
                break;
            case 5:
                line = board[2] + board[5] + board[8];
                break;
            case 6:
                line = board[0] + board[4] + board[8];
                break;
            case 7:
                line = board[2] + board[4] + board[6];
                break;
            }
            //For X winner
            if (line.equals("XXX")) {
                return "X";
            }

            // For O winner
            else if (line.equals("OOO")) {
                return "O";
            }
        }

        for (int a = 0; a < 9; a++) {
            if (Arrays.asList(board).contains(
                    String.valueOf(a + 1))) {
                break;
            }
            else if (a == 8) {
                return "draw";
            }
        }

       // To enter the X Or O at the exact place on board
        System.out.println(
            turn + "'s turn; enter a slot number to place "
            + turn + " in:");
        return null;
    }

    // To print out the board
    /* |---|---|---|
       | 1 | 2 | 3 |
       |-----------|
       | 4 | 5 | 6 |
       |-----------|
       | 7 | 8 | 9 |
       |---|---|---|*/

    static void printBoard()
    {
        System.out.println("|---|---|---|");
        System.out.println("| " + board[0] + " | "
                           + board[1] + " | " + board[2]
                           + " |");
        System.out.println("|-----------|");
        System.out.println("| " + board[3] + " | "
                           + board[4] + " | " + board[5]
                           + " |");
        System.out.println("|-----------|");
        System.out.println("| " + board[6] + " | "
                           + board[7] + " | " + board[8]
                           + " |");
        System.out.println("|---|---|---|");
    }

    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        board = new String[9];
        turn = "X";
        String winner = null;

        for (int a = 0; a < 9; a++) {
            board[a] = String.valueOf(a + 1);
        }

        System.out.println("Welcome to 3x3 Tic Tac Toe.");
        printBoard();

        System.out.println(
            "X will play first. Enter a slot number to place X in:");

        while (winner == null) {
            int numInput;

           // Exception handling.
           // numInput will take input from user like from 1 to 9.
           // If it is not in range from 1 to 9.
           // then it will show you an error "Invalid input."
            try {
                numInput = in.nextInt();
                if (!(numInput > 0 && numInput <= 9)) {
                    System.out.println(
                        "Invalid input; re-enter slot number:");
                    continue;
                }
            }
            catch (InputMismatchException e) {
                System.out.println(
                    "Invalid input; re-enter slot number:");
                continue;
            }

            // This game has two player x and O.
            // Here is the logic to decide the turn.
            if (board[numInput - 1].equals(
                    String.valueOf(numInput))) {
                board[numInput - 1] = turn;

                if (turn.equals("X")) {
                    turn = "O";
                }
                else {
                    turn = "X";
                }

                printBoard();
                winner = checkWinner();
            }
            else {
                System.out.println(
                    "Slot already taken; re-enter slot number:");
            }
        }

        // If no one win or lose from both player x and O.
        // then here is the logic to print "draw".
        if (winner.equalsIgnoreCase("draw")) {
            System.out.println(
                "It's a draw! Thanks for playing.");
        }

        // For winner -to display Congratulations! message.
        else {
            System.out.println(
                "Congratulations! " + winner
                + "'s have won! Thanks for playing.");
        }
      in.close();
    }
}

Output

Welcome to 3x3 Tic Tac Toe.
|---|---|---|
| 1 | 2 | 3 |
|-----------|
| 4 | 5 | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
X will play first. Enter a slot number to place X in:
2
|---|---|---|
| 1 | X | 3 |
|-----------|
| 4 | 5 | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
O's turn; enter a slot number to place O in:
5
|---|---|---|
| 1 | X | 3 |
|-----------|
| 4 | O | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
X's turn; enter a slot number to place X in:
1
|---|---|---|
| X | X | 3 |
|-----------|
| 4 | O | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
O's turn; enter a slot number to place O in:
3
|---|---|---|
| X | X | O |
|-----------|
| 4 | O | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
X's turn; enter a slot number to place X in:
8
|---|---|---|
| X | X | O |
|-----------|
| 4 | O | 6 |
|-----------|
| 7 | X | 9 |
|---|---|---|
O's turn; enter a slot number to place O in:
6
|---|---|---|
| X | X | O |
|-----------|
| 4 | O | O |
|-----------|
| 7 | X | 9 |
|---|---|---|
X's turn; enter a slot number to place X in:
9
|---|---|---|
| X | X | O |
|-----------|
| 4 | O | O |
|-----------|
| 7 | X | X |
|---|---|---|
O's turn; enter a slot number to place O in:
4
|---|---|---|
| X | X | O |
|-----------|
| O | O | O |
|-----------|
| 7 | X | X |
|---|---|---|
Congratulations! O's have won! Thanks for playing.

---

Happy Learning

Thanks For Reading! :)

SriParthu 💝💥