legacy code Tictactoe Java Re-engineering

java/Board.java

@@ -0,0 +1,28 @@
+class Board {
+    private String[] board;
+
+    public Board() {
+        board = new String[]{"0", "1", "2", "3", "4", "5", "6", "7", "8"};
+    }
+
+    public void printBoard() {
+        System.out.println(" " + board[0] + " | " + board[1] + " | " + board[2] +
+                "\n===+===+===\n" +
+                " " + board[3] + " | " + board[4] + " | " + board[5] +
+                "\n===+===+===\n" +
+                " " + board[6] + " | " + board[7] + " | " + board[8] + "\n");
+    }
+
+    public boolean isValidMove(int spot) {
+        return !board[spot].equals("X") && !board[spot].equals("O");
+    }
+
+    public void markSpot(int spot, String symbol) {
+        board[spot] = symbol;
+    }
+
+    public String[] getBoard() {
+        return board;
+    }
+}
+

java/ComputerPlayer.java

@@ -0,0 +1,29 @@
+import java.util.ArrayList;
+import java.util.concurrent.ThreadLocalRandom;
+
+class ComputerPlayer extends Player {
+    public ComputerPlayer(String symbol) {
+        super(symbol);
+    }
+
+
+    public void makeMove(Board board) {
+        System.out.println("Computer's turn...");
+        int bestMove = getBestMove(board);
+        board.markSpot(bestMove, getSymbol());
+    }
+
+    private int getBestMove(Board board) {
+
+        ArrayList<String> availableSpaces = new ArrayList<>();
+        String[] b = board.getBoard();
+        for (String s : b) {
+            if (!s.equals("X") && !s.equals("O")) {
+                availableSpaces.add(s);
+            }
+        }
+        int n = ThreadLocalRandom.current().nextInt(0, availableSpaces.size());
+        return Integer.parseInt(availableSpaces.get(n));
+    }
+}
+

java/Game.java

@@ -1,146 +1,6 @@
-import java.util.Scanner;
-import java.util.Arrays;
-import java.util.ArrayList;
-import java.util.concurrent.ThreadLocalRandom;
 
-/**
- * Tic-Tac-Toe: TWo-player console version.
- */
-public class Game {
-  // The game board and the game status
-  public static String[] board = {"0", "1", "2", "3", "4", "5", "6", "7", "8"};
-  public static int currentState;  // the current state of the game
-  public static String currentPlayer; // the current player
 
-  public static Scanner input = new Scanner(System.in); // the input Scanner
-
-  /** The entry main method (the program starts here) */
-  public static void main(String[] args) {
-    // Initialize the game-board and current status
-    initGame();
-    printBoard();
-    do {
-      getHumanSpot();
-      if (!gameIsOver() && !tie()) {
-        evalBoard();
-      }
-    } while (!gameIsOver() && !tie()); // repeat if not game-over
-    System.out.print("Game over\n");
-  }
-
-  /** Initializes the game */
-  public static void initGame() {
-    currentState = 0; // "playing" or ready to play
-    currentPlayer = "X";  // cross plays first
-  }
-
-  public static String nextPlayer() {
-    if (currentPlayer == "X") {
-      return "O";
-    } else {
-      return "X";
-    }
-  }
-
-  /** Update global variables "board" and "currentPlayer". */
-  public static void getHumanSpot() {
-    boolean validInput = false;  // for input validation
-    System.out.print("Enter [0-8]:\n");
-    do {
-      int spot = input.nextInt();
-      if (board[spot] != "X" && board[spot] != "O") {
-        board[spot] = "X";  // update game-board content
-        printBoard();
-        validInput = true;  // input okay, exit loop
-      }
-      currentPlayer = nextPlayer();  // cross plays first
-    } while (!validInput);  // repeat until input is valid
-  }
-
-  public static void evalBoard() {
-    boolean foundSpot = false;
-    do {
-      if (board[4] == "4") {
-        board[4] = "O";
-        foundSpot = true;
-      } else {
-        int spot = getBestMove();
-        if (board[spot] != "X" && board[spot] != "O") {
-          foundSpot = true;
-          board[spot] = "O";
-        } else {
-          foundSpot = false;
-        }
-      }
-    } while (!foundSpot);
-    printBoard();
-  }
-
-  /** Return true if the game was just won */
-  public static boolean gameIsOver() {
-    return board[0] == board[1] && board[1] == board[2] ||
-      board[3] == board[4] && board[4] == board[5] ||
-      board[6] == board[7] && board[7] == board[8] ||
-      board[0] == board[3] && board[3] == board[6] ||
-      board[1] == board[4] && board[4] == board[7] ||
-      board[2] == board[5] && board[5] == board[8] ||
-      board[0] == board[4] && board[4] == board[8] ||
-      board[2] == board[4] && board[4] == board[6];
-  }
-
-
-  public static int getBestMove() {
-    ArrayList<String> availableSpaces = new ArrayList<String>();
-    boolean foundBestMove = false;
-    int spot = 100;
-    for (String s: board) {
-      if (s != "X" && s != "O") {
-        availableSpaces.add(s);
-      }
-    }
-    for (String as: availableSpaces) {
-      spot = Integer.parseInt(as);
-      board[spot] = "O";
-      if (gameIsOver()) {
-        foundBestMove = true;
-        board[spot] = as;
-        return spot;
-      } else {
-        board[spot] = "X";
-        if (gameIsOver()) {
-          foundBestMove = true;
-          board[spot] = as;
-          return spot;
-        } else {
-          board[spot] = as;
-        }
-      }
-    }
-    if (foundBestMove) {
-      return spot;
-    } else {
-      int n = ThreadLocalRandom.current().nextInt(0, availableSpaces.size());
-      return Integer.parseInt(availableSpaces.get(n));
-    }
-  }
-
-  /** Return true if it is a draw (no more empty cell) */
-  // TODO: maybe there is an easeir way to check this
-  public static boolean tie() {
-    return board[0] != "0" &&
-           board[1] != "1" &&
-           board[2] != "2" &&
-           board[3] != "3" &&
-           board[4] != "4" &&
-           board[5] != "5" &&
-           board[6] != "6" &&
-           board[7] != "7" &&
-           board[8] != "8";
-  }
-
-  /** Print the game board */
-  public static void printBoard() {
-    System.out.println(" " + board[0] + " | " + board[1] + " | " + board[2] + "\n===+===+===\n" + " " + board[3] + " | " + board[4] + " | " + board[5] + "\n===+===+===\n" + " " + board[6] + " | " + board[7] + " | " + board[8] + "\n"); // print all the board cells
-  }
-
-}
+interface Game {
+  void startGame();
+  void switchPlayers();
+}

java/GameEngine.java

@@ -0,0 +1,44 @@
+class GameEngine implements Game {
+    private Board board;
+    private Player player1;
+    private Player player2;
+    private Player currentPlayer;
+    private GameRules gameRules;
+
+    public GameEngine(Board board, Player player1, Player player2) {
+        this.board = board;
+        this.player1 = player1;
+        this.player2 = player2;
+        this.currentPlayer = player1; 
+        this.gameRules = new GameRules(board);
+    }
+
+
+    public void startGame() {
+        board.printBoard();
+        while (true) {
+            currentPlayer.makeMove(board);
+            board.printBoard();
+
+            if (gameRules.isGameOver()) {
+                System.out.println("Player " + currentPlayer.getSymbol() + " wins!");
+                break;
+            }
+
+            if (gameRules.isTie()) {
+                System.out.println("It's a tie!");
+                break;
+            }
+
+            switchPlayers(); 
+        }
+    }
+
+
+    public void switchPlayers() {
+        currentPlayer = (currentPlayer == player1) ? player2 : player1;
+    }
+}
+
+
+

java/GameRules.java

@@ -0,0 +1,30 @@
+class GameRules {
+    private Board board;
+
+    public GameRules(Board board) {
+        this.board = board;
+    }
+
+    public boolean isGameOver() {
+        String[] b = board.getBoard();
+        return (b[0].equals(b[1]) && b[1].equals(b[2])) ||
+                (b[3].equals(b[4]) && b[4].equals(b[5])) ||
+                (b[6].equals(b[7]) && b[7].equals(b[8])) ||
+                (b[0].equals(b[3]) && b[3].equals(b[6])) ||
+                (b[1].equals(b[4]) && b[4].equals(b[7])) ||
+                (b[2].equals(b[5]) && b[5].equals(b[8])) ||
+                (b[0].equals(b[4]) && b[4].equals(b[8])) ||
+                (b[2].equals(b[4]) && b[4].equals(b[6]));
+    }
+
+    public boolean isTie() {
+        String[] b = board.getBoard();
+        for (int i = 0; i < b.length; i++) {
+            if (b[i].equals(String.valueOf(i))) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+

java/HumanPlayer.java

@@ -0,0 +1,33 @@
+import java.util.Scanner;
+
+class HumanPlayer extends Player{
+    private Scanner input = new Scanner(System.in);
+
+    public HumanPlayer(String symbol) {
+        super(symbol);
+    }
+
+
+    public void makeMove(Board board) {
+        boolean validInput = false;
+        int spot;
+        do {
+            System.out.print("Player " + getSymbol() + ", enter [0-8]: ");
+            while (!input.hasNextInt()) {
+                System.out.println("Please enter a valid number between 0 and 8.");
+                input.next(); 
+            }
+            spot = input.nextInt();
+            input.nextLine(); 
+
+            if (board.isValidMove(spot)) {
+                board.markSpot(spot, getSymbol());
+                validInput = true;
+            } else {
+                System.out.println("Invalid move, try again.");
+            }
+        } while (!validInput);
+    }
+}
+
+

java/Main.java

@@ -0,0 +1,26 @@
+import java.util.Scanner;
+
+public class Main {
+    public static void main(String[] args) {
+
+        try (Scanner scanner = new Scanner(System.in)) {
+            System.out.println("Welcome to Tic Tac Toe!");
+            System.out.print("Choose game mode (1 - Single Player, 2 - Two Player): ");
+            int mode = scanner.nextInt();
+
+            Board board = new Board();
+            Player player1 = new HumanPlayer("X");
+            GameEngine gameEngine;
+
+            if (mode == 1) {
+                Player computerPlayer = new ComputerPlayer("O");
+                gameEngine = new GameEngine(board, player1, computerPlayer);
+            } else {
+                Player player2 = new HumanPlayer("O");
+                gameEngine = new GameEngine(board, player1, player2);
+            }
+
+            gameEngine.startGame();
+        } 
+    }
+}

java/Player.java

@@ -0,0 +1,13 @@
+public abstract class  Player {
+    protected String symbol;
+
+    public Player(String symbol) {
+        this.symbol = symbol;
+    }
+
+    public String getSymbol() {
+        return symbol;
+    }
+
+    public abstract void makeMove(Board board);
+}