(Game: play a tic-tac-toe game) In a game of tic-tac-toe, two players take turns marking an available cell in a 3 * 3 grid with their respective tokens (either X or O)

/*********************************************************************************
* (Game: play a tic-tac-toe game) In a game of tic-tac-toe, two players take     *
* turns marking an available cell in a 3 * 3 grid with their respective tokens   *
* (either X or O). When one player has placed three tokens in a horizontal,      *
* vertical, or diagonal row on the grid, the game is over and that player has    *
* won. A draw (no winner) occurs when all the cells on the grid have been filled *
* with tokens and neither player has achieved a win. Create a program for        *
* playing tic-tac-toe. The program prompts two players to enter an X token       *
* and O token alternately. Whenever a token is entered, the program redisplays   *
* the board on the console and determines the status of the game (win, draw, or  *
* continue).                                                                     *
*********************************************************************************/
import java.util.Scanner;

public class Exercise_08_09 {
	/** Main method */
	public static void main(String[] args) {
		// Create a empty board
		String [][] board = getBoard();

		// Create two players token
		String[] tokens = {" X "," O "};

		int result; // game status result

		// Repeat while result is continue
		do {
			// Display board
			print(board);

			// Get available cell to mark
			int[] cell = getCell(board, tokens[0]);
			
			// Mark available cell with player's token
			placeToken(board, cell, tokens[0]);
	
			// Determine game status
			result = gameStatus(board, tokens[0]);

			// If status is continue make next player take turn
			if (result == 2) {
				swap(tokens);
			}

		} while(result == 2);

		// Display board
		print(board);

		// Display game results
		if (result == 0)
			System.out.println(tokens[0] + "player won");
		else
			System.out.println("Players draw");

	}

	/** gameStatus determines the status of the game (win, draw, or continue) */
	public static int gameStatus(String[][] m, String e) {
		if (isWin(m, e))
			return 0; // Win
		else if (isDraw(m))
			return 1; // Draw
		else
			return 2; // Continue
	}

	/** isWin returns true if player has placed three tokens in, 
	    a horizontal vertical, or diagonal row on the grid */
	public static boolean isWin(String[][] m, String t) { 
		return isHorizontalWin(m, t) || isVerticalWin(m, t) || isDiagonalWin(m, t);
	}

	/** isHorizontalWin returns true if player has 
	    placed three tokens in a horizontal row */
	public static boolean isHorizontalWin(String[][] m, String t) {
		for (int i = 0; i < m.length; i++) {
			int count = 0;
			for (int j = 0; j < m[i].length; j++) {
				if (m[i][j] == t)
					count++;
			}
			if (count == 3)
				return true;
		}
		return false;
	}

	/** isVerticalWin returns true if player has 
	    placed three tokens in a vertical row */
	public static boolean isVerticalWin(String[][] m, String t) {
		for (int i = 0; i < m.length; i++) {
			int count = 0;
			for (int j = 0; j < m[i].length; j++) {
				if (m[j][i] == t)
					count++;
			}
			if (count == 3)
				return true;
		}
		return false;
	}

	/** isDiagonalWin returns true if player has 
	    placed three tokens in a diagonal row */
	public static boolean isDiagonalWin(String[][] m, String t) {
		int count = 0;
		for (int i = 0; i < m.length; i++) {
			if (m[i][i] == t)
				count++;
			if (count == 3)
				return true;
		}

		count = 0;
		for (int i = 0, j = m[i].length - 1; j >= 0 ; j--, i++) {
			if (m[i][j] == t)
				count++;
			if (count == 3)
				return true;
		}
		return false;
	}

	/** isDraw returns true if all the cells on the grid have been  
		 filled with tokens and neither player has achieved a win */
	public static boolean isDraw(String[][] m) {
		for (int i = 0; i < m.length; i++) {
			for (int j = 0; j < m[i].length; j++) {
				if (m[i][j] == "   ")
					return false;
			}
		}
		return true;
	}

	/** swap swaps the elements in an arrray */
	public static void swap(String[] p) {
		String temp = p[0];
		p[0] = p[1];
		p[1] = temp;
	}

	/** placeToken fills the matrix cell with the player's token */
	public static void placeToken(String[][] m, int[] e, String t) {
		m[e[0]][e[1]] = t;
	}

	/** getCell returns a valid cell input by user */
	public static int[] getCell(String[][] m, String t) {
		// Create a Scanner
		Scanner input = new Scanner(System.in);
		int[] cell = new int[2]; // Cell row and column

		// Prompt player to enter a token
		do {
			System.out.print("Enter a row(0, 1, or 2) for player " + t + ": ");
			cell[0] = input.nextInt();
			System.out.print("Enter a column(0, 1, or 2) for player " + t + ": ");
			cell[1] = input.nextInt();

		} while (!isValidCell(m, cell));
		return cell;
	}

	/** isValidCell returns true is cell is empty and is in a 3 x 3 array */
	public static boolean isValidCell(String[][] m, int[] cell) {
		for (int i = 0; i < cell.length; i++) {
			if (cell[i] < 0 || cell[i] >= 3) {
				System.out.println("Invalid cell");
				return false;
			}
		}
		if (m[cell[0]][cell[1]] != "   ") {
			System.out.println(
				"\nRow " + cell[0] + " column " + cell[1] + " is filled");
			return false;
		}
		return true;		
	}

	/** getBoard returns a 3 x 3 array filled with blank spaces */
	public static String[][] getBoard() {
		String[][] m = new String[3][3];
		for (int i = 0; i < 3; i++) {
			for (int j = 0; j < 3; j++) {
				m[i][j] = "   ";
			}
		}
		return m;
	}

	/** print displays the board */
	public static void print(String[][] m) {
		System.out.println("\n-------------");
		for (int i = 0; i < m.length; i++) {
			for (int j = 0; j < m[i].length; j++) {
				System.out.print("|" + m[i][j]);
			}
			System.out.println("|\n-------------");
		}
	}
}