TicTacToe.java

import java.util.Scanner;

public class TicTacToe {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);

		char player = '0';
		char[][] board = emptyBoard();

		displayWelcome(board);
		while (!gameOver(board, player)) {
			player = nextPlayer(player);
			takeTurn(s, board, player);
			displayBoard(board);
		}

		displayEndGame(board, player);

		s.close();

	}

	public static char[][] emptyBoard() {
		char[][] board = new char[3][3];
		for (int i = 0; i < board.length; i++) {
			for (int j = 0; j < board[i].length; j++) {
				board[i][j] = '_';
			}
		}
		return board;
	}

	public static boolean winByDiagonal(char[][] board, char player) {
		boolean primaryDiagonal = board[0][0] == player && board[1][1] == player && board[2][2] == player;
		boolean secondaryDiagonal = board[0][2] == player && board[1][1] == player && board[2][0] == player;
		return primaryDiagonal || secondaryDiagonal;
	}

	public static boolean winByDiag(char[][] board, char player) {
		boolean win = true;
		for (int j = board.length - 1; j >= 0; j--) {
			int i = board.length - j - 1;
			win = win && board[i][j] == player;
		}
		return win;
	}

	public static boolean winByLine(char[][] board, char player) {
		boolean line1 = board[0][0] == player && board[0][1] == player && board[0][2] == player;
		boolean line2 = board[1][0] == player && board[1][1] == player && board[1][2] == player;
		boolean line3 = board[2][0] == player && board[2][1] == player && board[2][2] == player;
		return line1 || line2 || line3;
	}

	public static boolean winByColumn(char[][] board, char player) {
		boolean column1 = board[0][0] == player && board[1][0] == player && board[2][0] == player;
		boolean column2 = board[0][1] == player && board[1][1] == player && board[2][1] == player;
		boolean column3 = board[0][2] == player && board[1][2] == player && board[2][2] == player;
		return column1 || column2 || column3;
	}

	public static boolean draw(char[][] board) {
		for (int i = 0; i < board.length; i++) {
			for (int j = 0; j < board[i].length; j++) {
				if (board[i][j] == '_') {
					return false;
				}
			}
		}
		return true;
	}

	public static boolean gameOver(char[][] board, char player) {
		return winByDiagonal(board, player) || winByLine(board, player) || winByColumn(board, player) || draw(board);
	}

	public static char nextPlayer(char currentPlayer) {
		if (currentPlayer == 'x') {
			return '0';
		} else {
			return 'x';
		}
	}

	public static void takeTurn(Scanner s, char[][] board, char player) {

		if (player == 'x') {
			humanTurn(s, board, player);
		} else {
			aiTurn(board, player);
		}
	}

	public static int readNum(Scanner sc) {
		if (!sc.hasNextInt()) {
			System.out.println("Introduceti un numar intre 0 si 2");
			return readNum(sc);
		}

		int number = sc.nextInt();
		if (number < 0 || number > 2) {
			System.out.println("Introduceti un numar intre 0 si 2");
			return readNum(sc);
		}

		return number;
	}

	public static void humanTurn(Scanner s, char[][] board, char player) {
		System.out.println("Randul lui " + player);
		System.out.print("i: ");
		int i = readNum(s);
		System.out.println();
		System.out.print("j: ");
		int j = readNum(s);

		if (board[i][j] == '_') {
			board[i][j] = player;
		} else {
			System.out.println("Pozitie ocupata deja, mai incearca");
			humanTurn(s, board, player);
		}
	}

	public static int randomPosition() {
		double procent = Math.random();
		if(procent < 1.0 / 3.0) {
			return 0;
		}
		if(procent < 2.0/3.0) {
			return 1;
		}
		return 2;
	}

	public static void aiTurn(char[][] board, char player) {
		int i = randomPosition();
		int j = randomPosition();

		if (board[i][j] == '_') {
			board[i][j] = player;
		} else {
			aiTurn(board, player);
		}

	}

	public static void displayBoard(char[][] board) {
		for (int i = 0; i < board.length; i++) {
			for (int j = 0; j < board[i].length; j++) {
				System.out.print(board[i][j] + " ");
			}
			System.out.println();
		}
	}

	public static void displayEndGame(char[][] board, char player) {
		displayBoard(board);

		if (draw(board)) {
			System.out.println("Ramiza pe tura lui " + player);
		} else {
			System.out.println("Felicitari " + player + ", ai castigat!");
		}
	}

	public static void displayWelcome(char[][] board) {
		System.out.println("Bun venit la X si Zero");
		displayBoard(board);
	}

}