如何修复井字棋游戏加载时的Java NumberFormatException错误？

错误信息 #

Exception in thread "main" java.lang.NumberFormatException: For input string: "Matt"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
        at java.lang.Integer.parseInt(Integer.java:580)
        at java.lang.Integer.parseInt(Integer.java:615)
        at Multiplayer.multiplayer(Multiplayer.java:41)
        at TicTacToe.MUltiplayer_Game(TicTacToe.java:107)
        at TicTacToe.main(TicTacToe.java:38)

问题根源 #

• 保存与加载字段顺序不匹配：保存时写入顺序为p1→p2→currRound→turn，但加载时读取顺序为currRound→p1→p2→turn，导致把玩家名称（字符串）当成回合数（整数）解析，触发NumberFormatException。
• 棋盘加载索引错误：读取棋盘行数据时，错误使用行索引i获取列数组row的元素，应使用列索引j。

修复后的完整代码 #

//Creates a new 3x3 Array grid.
char[][] ticTacToeBoard = new char[3][3];
char turn = 'X';
String winner;

//Runs Multiplayer.
public void multiplayer() {
    Scanner input = new Scanner(System.in);

    String p1 = "", p2 = "";
    int currRound = 0;
    String loadOption;

    //Default as not used.
    boolean fileUsed = false;
    // Ask the user if they want to load a saved game
    System.out.print("Do you want to load a saved game? (y/n): ");
    loadOption = input.next();

    //If user wants to load file.
    if (loadOption.substring(0, 1).equalsIgnoreCase("Y")) {
        String loadFile = "tictactoe_save.txt";
        try (Scanner reader = new Scanner(new File(loadFile))) {
            fileUsed = true;
            // 修正读取顺序，与保存顺序一致
            p1 = reader.nextLine();
            p2 = reader.nextLine();
            currRound = Integer.parseInt(reader.nextLine());
            turn = reader.nextLine().charAt(0);
            System.out.println(p1 + ", " + p2 + ", " + turn + ", " + currRound); //For testing
            
            // 加载棋盘数据
            for (int i = 0; i < ticTacToeBoard.length; i++) {
                String[] row = reader.nextLine().split(" ");
                for (int j = 0; j < Math.min(ticTacToeBoard[0].length, row.length); j++) {
                    // 修正索引错误：使用列索引j而非行索引i
                    ticTacToeBoard[i][j] = row[j].charAt(0);
                }
            }
            displayBoard(ticTacToeBoard);
            reader.close();
        } catch (IOException e) {
            System.out.println("Error: File not found.");
        }
    }
    if (!fileUsed) {
        //If user does not want to load a save file.
        System.out.println("*Multiplayer active*");
        System.out.print("Enter your name, Player 1: ");
        p1 = input.next();
        System.out.print("Enter your name, Player 2: ");
        p2 = input.next();
        System.out.println("\nLets play! Your goal is to get three-in-a-row \nwith your pieces to win the game! "
                + "Ties can occure, so be smart! \nPlayer 1 plays X pieces; Player 2 plays O pieces. Have fun!");
        
        // 初始化空棋盘
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                ticTacToeBoard[i][j] = ' ';
            }
        }
        displayBoard(ticTacToeBoard);

        currRound = 0;
        turn = 'X';
    }

    // 根据turn初始化当前玩家
    String currPlayer = turn == 'X' ? p1 : p2;
    
    //Game runs
    for (int round = currRound; round < 9; round++) {

        //User selects and places a piece that is legal.
        selectArea_Human(ticTacToeBoard, turn, currPlayer);

        //Updates ticTacToeBoard.
        System.out.println("-----------------------------------");
        displayBoard(ticTacToeBoard);

        //Checks if three-in-a-row has occured.
        if (isThree_In_A_Row(turn, ticTacToeBoard)) {
            break;
        }

        //Next players turn.
        turn = (turn == 'X') ? 'O' : 'X';
        currPlayer = (turn == 'X') ? p1 : p2;

        // Save the game state to a file after every turn.
        String saveFile = "tictactoe_save.txt";
        try (FileWriter writer = new FileWriter(saveFile)) {
            writer.write(p1 + "\n"); // Save p1 name.
            writer.write(p2 + "\n"); // Save p2 name.
            writer.write((round + 1) + "\n"); // 保存下一个回合数，确保加载后正确续玩
            writer.write(turn + "\n"); // Save the current turn.
            for (int i = 0; i < ticTacToeBoard.length; i++) {
                for (int j = 0; j < ticTacToeBoard[0].length; j++) {
                    writer.write(ticTacToeBoard[i][j] + " ");
                }
                writer.write("\n");
            }
            System.out.println("Game successfully saved.");
        } catch (IOException e) {
            System.out.println("Error: File not found.");
        }
    }

    //Checks for tie game; Otherwise declares the winner.
    if (!isThree_In_A_Row(turn, ticTacToeBoard)) {
        System.out.println("The game is over.");
        System.out.println("It's a tie!");
    } else {
        winner = currPlayer;
        System.out.println("The game is over.");
        System.out.println("The winner is " + winner + "!");
    }
    input.close();
}

额外修复说明 #

• 补充turn变量初始化，避免未定义错误
• 修正当前玩家初始化逻辑，根据加载的turn值正确匹配玩家
• 保存回合数改为round + 1，确保加载后从下一个回合继续游戏
• 调整棋盘显示时机，加载完成后再显示存档棋盘
• 关闭输入扫描器，避免资源泄漏

内容的提问来源于stack exchange，提问作者Caleb Murnan