Tic Tac Toe

The goal of the Tic Tac Toe project is to make a Tic Tac Toe game that you can play in your Codespace, similar to the way Twenty Questions worked. You will print the board using System.out.println and read input from the user via java.util.Scanner (check out your Twenty Questions project for some useful bits of code.) You may also find the method Integer.parseInt useful—it takes a String containing digits and returns and int. Thus Integer.parseInt("1234") would return the int value 1234

Basic requirements

Print the board to the screen before each move.
Accept human input for the move to make and reprint the board with the move made.
Automatically switch between Xs and Os.
Detect and disallow moves in occupied squares. (You will probably want to use an array to record which squares have been played in. You can use a single 9-element array and a bit of math or you can peek ahead at Unit 8 to see how to make 2d arrays.)
Detect wins and ties and end the game after printing a message about the result.

Beyond the basics

If you finish the basics, there are two next steps you can persue: AI player or Ultimate Tic Tac Toe.

Tic Tac Toe AI

For an AI you can write code to play one of the players (or both, I suppose). Start simple, such as a computer player that just plays and random empty squares. Then you can write one that uses a heuristic such as picking the corners and the center when available. That will play okay but not perfectly. If you really want to go to town, you can write an algorithm that explores the tree of possible moves to find the best move.

Ultimate Tic Tac Toe

Ultimate Tic Tac Toe is a variant of Tic Tac Toe where the game is played on a large board with each square containing a smaller Tic Tac Toe board. Players play simultaneously on the big board and on the nine smaller boards, claiming squares on the big board by winning the small boards. Wikipedia has a good synopsis of the rules.

Because of the more complex board and rules about when a certain small board must be played on and when the player to move gets a free choice the UI for Ultimate Tic Tac Toe is more complex but it should be possible to make a reasonable UI even in a text-based environment.

Note that writing Ultimate Tic Tac Toe is an excellent chance to see if you've made a good TicTacToe class, because an obvious way to manage the small boards is to make nine instances of your TicTacToe class to represent each of the small boards. Though some things are different, insofar as players don't necessarily alternate moves on a given small board, leading to states that could never arise in a regular Tic Tac Toe game.