Tic-Tac-Toe is a simple two-player game played on a 3×3 grid. Players take turns placing X and O on the board, with the goal of getting three identical marks in a row, column, or diagonal. In this project, we will build a console-based Tic-Tac-Toe game in Java for two players.
- Uses a 3×3 board with positions numbered from 1 to 9.
- Players take turns selecting a position to place their mark.
- The game continues until a player wins or all positions are filled, resulting in a tie.
Prerequisites
- Java Development Kit (JDK 8 or higher) installed
- Any IDE like IntelliJ IDEA, Eclipse IDE, or terminal
- Basic knowledge of Java (arrays, loops, conditionals, Scanner)
- Methods: Used to organize different parts of the game logic.
Game Board Layout
The game board layout will look something like this:
|---|---|---|
| 1 | 2 | 3 |
|-----------|
| 4 | 5 | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
How to Play the Game
The steps to play the game are listed below:
- Both players choose either X or O to mark their cells.
- There will be a 3x3 grid with numbers assigned to each of the 9 cells.
- The player who chooses X begins to play first.
- The player enters the cell number where they wish to place X.
- Now, both O and X play alternatively until one of the two wins.
- Winning criteria: Whenever any of the two players has fully filled one row/ column/ diagonal with their symbol (X/ O), they win and the game ends.
- If neither of the two players wins, the game is said to have ended in a draw.
Sample Input: Enter a slot number to place X in: 3
Sample Output:
|---|---|---|
| 1 | 2 | X |
|-----------|
| 4 | 5 | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
Sample Input:
Now, O's turn, Enter a slot number to place O in: 5
Sample Output:
|---|---|---|
| 1 | 2 | X |
|-----------|
| 4 | O | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
So, like this game will be continued.
Project Implementation
import java.util.*;
public class Geeks {
static String[] board;
static String turn;
// CheckWinner method will decide the winner
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";
}
}
System.out.println(turn + "'s turn; enter a slot number to place " + turn + " in:");
return null;
}
// To print the board
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;
try {
numInput = in.nextInt();
// Check range
if (!(numInput > 0 && numInput <= 9)) {
System.out.println("Invalid input; re-enter slot number:");
continue;
}
// Check if slot is available
if (board[numInput - 1].equals(String.valueOf(numInput))) {
board[numInput - 1] = turn;
// Toggle turn
turn = turn.equals("X") ? "O" : "X";
printBoard();
winner = checkWinner();
} else {
System.out.println("Slot already taken; re-enter slot number:");
}
} catch (InputMismatchException e) {
System.out.println("Invalid input; re-enter slot number:");
in.nextLine(); // Consume invalid input to prevent infinite loop
}
}
// Final result
if (winner.equalsIgnoreCase("draw")) {
System.out.println("It's a draw! Thanks for playing.");
} else {
System.out.println("Congratulations! " + winner + "'s have won! Thanks for playing.");
}
in.close();
}
}
Output:
Below is the output of the above program :
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:
3
|---|---|---|
| 1 | 2 | X |
|-----------|
| 4 | 5 | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
O's turn; enter a slot number to place O in:
5
|---|---|---|
| 1 | 2 | X |
|-----------|
| 4 | O | 6 |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
X's turn; enter a slot number to place X in:
6
|---|---|---|
| 1 | 2 | X |
|-----------|
| 4 | O | X |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
O's turn; enter a slot number to place O in:
1
|---|---|---|
| O | 2 | X |
|-----------|
| 4 | O | X |
|-----------|
| 7 | 8 | 9 |
|---|---|---|
X's turn; enter a slot number to place X in:
9
|---|---|---|
| O | 2 | X |
|-----------|
| 4 | O | X |
|-----------|
| 7 | 8 | X |
|---|---|---|
Congratulations! X's have won! Thanks for playing.
Steps to Run on IntelliJ IDE
- Open the project in IntelliJ IDEA.
- Open the Java class containing the main() method.
- Right-click inside the class or on the class file.
- Select Run 'Geeks.main()'.
- The game will start in the Run console.
IntelliJ IDEA automatically saves changes when required.
We can check below screenshot for your reference.
