Add TicTacToe game in Java

java/TicTacToe.java

@@ -0,0 +1,167 @@
+// A simple program to demonstrate Tic-Tac-Toe Game.
+import java.util.*;
+
+public class TicTacToe {
+
+	static String[] board;
+	static String turn;
+
+
+	// CheckWinner method will
+	// decide the combination
+	// of three box given below.
+
+	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";
+			}
+		}
+
+	// To enter the X Or O at the exact place on board.
+		System.out.println(
+			turn + "'s turn; enter a slot number to place "
+			+ turn + " in:");
+		return null;
+	}
+
+
+
+	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;
+
+		// Exception handling.
+		// numInput will take input from user like from 1 to 9.
+		// If it is not in range from 1 to 9.
+		// then it will show you an error "Invalid input."
+			try {
+				numInput = in.nextInt();
+				if (!(numInput > 0 && numInput <= 9)) {
+					System.out.println(
+						"Invalid input; re-enter slot number:");
+					continue;
+				}
+			}
+			catch (InputMismatchException e) {
+				System.out.println(
+					"Invalid input; re-enter slot number:");
+				continue;
+			}
+
+			// This game has two player x and O.
+			// Here is the logic to decide the turn.
+			if (board[numInput - 1].equals(
+					String.valueOf(numInput))) {
+				board[numInput - 1] = turn;
+
+				if (turn.equals("X")) {
+					turn = "O";
+				}
+				else {
+					turn = "X";
+				}
+
+				printBoard();
+				winner = checkWinner();
+			}
+			else {
+				System.out.println(
+					"Slot already taken; re-enter slot number:");
+			}
+		}
+
+		// If no one win or lose from both player x and O.
+		// then here is the logic to print "draw".
+		if (winner.equalsIgnoreCase("draw")) {
+			System.out.println(
+				"It's a draw! Thanks for playing.");
+		}
+
+		// For winner -to display Congratulations! message.
+		else {
+			System.out.println(
+				"Congratulations! " + winner
+				+ "'s have won! Thanks for playing.");
+		}
+	}
+}