How to make a Tic Tac Toe (noughts and crosses) game in Java

It's time to put our knowledge into practice to do something really cool and useful:
The Tic Tac Toe game in Java! Also known as noughts and crosses!

This is a simple version, to be played with two people. Note that in a simple Java application like this, the result came out around 300 lines of code.

If you are Java programmer, click to see the full commented code and explanation about the Tic Tac Toe Java Game creation.

Yes, there is a strategy we can adopt (or the computer may adopt) to never lose a game of tic tac toe:
http://en.wikipedia.org/wiki/Tic-tac-toe

How to play our Tic Tac Toe game made in Java

First, as this version is simpler, you can only play Human vs Human. Soon we will teach how to program the computer to play.

So choice as Player 1 and Player 2 as humans.
After that, just select the line and column of the board where you want to play.
Recalling that Player 1 is always the 'X' and Player 2 is always the 'O'.

After that, just play normally. When the player complete a line, column or diagonal, the game stops.
O when the tray is full and a tie happens.

For Java programmers: How to create a Tic Tac Toe in Java

Our Tic Tac Toe game have over 300 lines of Java code, we will explain each class, method and idea in another post:
Code about how to create the Tic Tac Toe in Java

Code Java Tic Tac Toe, text mode Human x Human

Create a project named 'TicTacToe', and add the following 6 classes, run and be happy.


-->TicTacToe.java

public class TicTacToe {

    public static void main(String[] args) {
        Game game = new Game();
        
    }
}

-->Board.java

public class Board {
    private int[][] Board= new int[3][3];
    
    public Board(){
        clearBoard();
    }
    
    public void clearBoard(){
        for(int line=0 ; line<3 ; line++)
            for(int column=0 ; column<3 ; column++)
                Board[line][column]=0;
    }
    
    public void showBoard(){
        System.out.println();
        for(int line=0 ; line<3 ; line++){
        
            for(int column=0 ; column<3 ; column++){
                
                if(Board[line][column]==-1){
                    System.out.print(" X ");
                }
                if(Board[line][column]==1){
                    System.out.print(" O ");
                }
                if(Board[line][column]==0){
                    System.out.print("   ");
                }
                
                if(column==0 || column==1)
                    System.out.print("|");
            }
            System.out.println();
        }
                
    }

    public int getPosition(int[] attempt){
        return Board[attempt[0]][attempt[1]];
    }
    
    public void setPosition(int[] attempt, int player){
        if(player == 1)
            Board[attempt[0]][attempt[1]] = -1;
        else
            Board[attempt[0]][attempt[1]] = 1;
    }

    public int checkLines(){
        for(int line=0 ; line<3 ; line++){

            if( (Board[line][0] + Board[line][1] + Board[line][2]) == -3)
                return -1;
            if( (Board[line][0] + Board[line][1] + Board[line][2]) == 3)
                return 1;
        }
        
        return 0;
                
    }
    
    public int checkColumns(){
        for(int column=0 ; column<3 ; column++){

            if( (Board[0][column] + Board[1][column] + Board[2][column]) == -3)
                return -1;
            if( (Board[0][column] + Board[1][column] + Board[2][column]) == 3)
                return 1;
        }
        
        return 0;
                
    }
    
    public int checkDiagonals(){
        if( (Board[0][0] + Board[1][1] + Board[2][2]) == -3)
            return -1;
        if( (Board[0][0] + Board[1][1] + Board[2][2]) == 3)
            return 1;
        if( (Board[0][2] + Board[1][1] + Board[2][0]) == -3)
            return -1;
        if( (Board[0][2] + Board[1][1] + Board[2][0]) == 3)
            return 1;
        
        return 0;
    }

    public boolean fullBoard(){
        for(int line=0 ; line<3 ; line++)
            for(int column=0 ; column<3 ; column++)
                if( Board[line][column]==0 )
                    return false;
        return true;
    }
}

-->Game.java

import java.util.Scanner;

public class Game {
    private Board board;
    private int turn=1, who=1;
    private Player player1;
    private Player player2;
    public Scanner input = new Scanner(System.in);

    
    public Game(){
        board = new Board();
        startPlayers();
        
        while( Play() );
    }
    
    public void startPlayers(){
        System.out.println("Who will be player1 ?");
        if(choosePlayer() == 1)
            this.player1 = new Human(1);
        else
            this.player1 = new Computer(1);
        
        System.out.println("----------------------");
        System.out.println("Who will be Player 2 ?");
        
        if(choosePlayer() == 1)
            this.player2 = new Human(2);
        else
            this.player2 = new Computer(2);
        
    }
    
    public int choosePlayer(){
        int option=0;
        
        do{
            System.out.println("1. Human");
            System.out.println("2. Computer\n");
            System.out.print("Option: ");
            option = input.nextInt();
            
            if(option != 1 && option != 2)
                System.out.println("Invalid Option! Try again");
        }while(option != 1 && option != 2);
        
        return option;
    }
    
    public boolean Play(){
        board.showBoard();
        if(won() == 0 ){
            System.out.println("----------------------");
            System.out.println("\nTurn "+turn);
            System.out.println("It's turn of Player " + who() );
            
            if(who()==1)
                player1.play(board);
            else
                player2.play(board);
            
            
            if(board.fullBoard()){
                System.out.println("Full Board. Draw!");
                return false;
            }
            who++;
            turn++;

            return true;
        } else{
            if(won() == -1 )
                System.out.println("Player 1 won!");
            else
                System.out.println("Player 2 won!");
            
            return false;
        }
            
    }
    
    public int who(){
        if(who%2 == 1)
            return 1;
        else
            return 2;
    }
    
    public int won(){
        if(board.checkLines() == 1)
            return 1;
        if(board.checkColumns() == 1)
            return 1;
        if(board.checkDiagonals() == 1)
            return 1;
        
        if(board.checkLines() == -1)
            return -1;
        if(board.checkColumns() == -1)
            return -1;
        if(board.checkDiagonals() == -1)
            return -1;
        
        return 0;
    }
    
    
}

-->Player.java

public abstract class Player {
    
    protected int[] attempt = new int[2];
    protected int player;

    
    public Player(int player){
        this.player = player;
    }
    
    public abstract void play(Board board);
    
    public abstract void Try(Board board);

    public boolean checkTry(int[] attempt, Board board){
        if(board.getPosition(attempt) == 0)
            return true;
        else
            return false;

            
    }
    
}

-->Human.java

import java.util.Scanner;

public class Human extends Player{
    public Scanner input = new Scanner(System.in);
    
    public Human(int player){
        super(player);
        this.player = player;
        System.out.println("Player 'Human' created!");
    }
    
    @Override
    public void play(Board board){
        Try(board);
        board.setPosition(attempt, player);
    }
    
    @Override
    public void Try(Board board){
        do{
            do{
                System.out.print("Line: ");
                attempt[0] = input.nextInt();
                
                if( attempt[0] > 3 ||attempt[0] < 1)
                    System.out.println("Invalid line. It's 1, 2 or 3");
                
            }while( attempt[0] > 3 ||attempt[0] < 1);
            
            do{
                System.out.print("Column: ");
                attempt[1] = input.nextInt();
                
                if(attempt[1] > 3 ||attempt[1] < 1)
                    System.out.println("Invalid column. É 1, 2 or 3");
                
            }while(attempt[1] > 3 ||attempt[1] < 1);
            
            attempt[0]--; 
            attempt[1]--;
            
            if(!checkTry(attempt, board))
                System.out.println("Placed already marked. Try other.");
        }while( !checkTry(attempt, board) );
    }
}

-->Computer.java

public class Computer extends Player{
    
    public Computer(int player){
        super(player);
        System.out.println("Player 'Computer' created");
    }
    
    @Override
    public void play(Board board){
        
    }
    
    @Override
    public void Try(Board board){
        
    }
}