修复Java掷骰子游戏中的循环中断异常-java教程-PHP中文网

修复Java掷骰子游戏中的循环中断异常

碧海醫心

发布： 2025-09-11 22:11:01

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修复java掷骰子游戏中的循环中断异常

本文旨在帮助Java初学者解决在掷骰子游戏中循环中断时遇到的异常问题。通过分析代码，找出导致异常的原因，并提供修改后的代码示例，确保游戏在玩家选择退出或资金不足时能够正常结束，并展示游戏结束时的信息。

在提供的代码中，主要问题集中在游戏循环的退出条件和System.out.printf的使用上。以下将详细解释并提供修改后的代码。

问题分析与修复

循环退出条件

原代码中，循环的退出条件是playAgain && total > 0。这意味着只有当playAgain为true且total大于0时，循环才会继续。虽然在循环内部有break语句用于处理total <= 9和again.equalsIgnoreCase("n")的情况，但逻辑上没有错误。问题在于，当输入无效字符时，again变量的值未被正确更新，导致可能进入死循环。

修改后的代码示例：

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```
while (playAgain && total > 0) {
    // ... (游戏逻辑) ...

    if (total <= 9) {
        break;
    }

    System.out.println("Keep playing (y/Y or n/N)? ");
    in.nextLine(); // Consume the newline character
    String again = in.nextLine();

    if (again.equalsIgnoreCase("y")) {
        playAgain = true;
    } else if (again.equalsIgnoreCase("n")) {
        playAgain = false; // Set playAgain to false to exit the loop
        break;
    } else {
        System.out.println("Invalid character input, try again:");
        // No need to read input again here. The loop will continue and ask again.
    }
}
```
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注意事项：
- 在读取字符串之前，使用in.nextLine()来消耗掉之前in.nextInt()留下的换行符，避免影响后续的输入。
- 当玩家输入 "n" 时，将 playAgain 设置为 false，确保循环能够正常退出。
- 当输入无效字符时，不需要再次读取输入。循环会自动回到开始，再次提示用户输入。
System.out.printf 异常

原始代码中使用System.out.printf("Based on your play, the probability of winning is %.2%", winPercent);，这可能会导致MissingFormatArgumentException异常，因为%.2%需要一个参数，而winPercent已经被用作格式化的数值。

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正确的做法是使用System.out.println进行字符串拼接，或者使用String.format方法。

修改后的代码示例：

立即学习“Java免费学习笔记（深入）”；
```
// 方法一：使用 System.out.println 进行字符串拼接
System.out.println("Based on your play, the probability of winning is " + String.format("%.2f", winPercent) + "%.");

// 方法二：使用 String.format
//System.out.printf("Based on your play, the probability of winning is %.2f%%", winPercent);
```
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解释：
- 方法一使用 String.format("%.2f", winPercent) 将 winPercent 格式化为保留两位小数的浮点数，然后与字符串拼接。
- 方法二使用 String.format 和 %% 来输出百分号。

完整修改后的代码

import java.util.Random;
import java.util.Scanner;

public class GameOfCrapsTester {

    static Scanner in = new Scanner(System.in);
    static Random rand = new Random();

    public static void main(String[] args) {

        System.out.println("Welcome to the game of Craps");
        System.out.println(" ");
        System.out.println("The house has given you a starting balance of $500");
        System.out.println("On each round, you will make a whole number wager.");
        System.out.println("The minimum wager is $10, and the maximum wager is your remaining balance.");
        System.out.println(" ");
        System.out.println("You may keep playing until you decide to cash in, or");
        System.out.println("    you can't cover the minimum wager.");
        System.out.println("Good Luck!");

        boolean win;
        double wins = 0, numOfGames = 0;
        int total = 500;

        // Come out roll and set point value
        int pointValue = 0;
        boolean playAgain = true;
        while (playAgain && total > 0) {
            System.out.println(" ");
            System.out.println("Your balance is $" + total);
            System.out.println(" ");
            System.out.println("Place your bet: $");

            // Get and check wager placed
            int bet = in.nextInt();
            in.nextLine(); // Consume newline
            while (bet > total || bet < 10) {
                if (bet < 10) {
                    System.out.println("Bet must be larger than $10.");
                }
                System.out.println("I'm sorry, that's not a valid wager; please re-enter: ");
                bet = in.nextInt();
                in.nextLine(); // Consume newline
            }
            int num = rollDice();
            if ((num >= 4 && num <= 10 && num != 7) || num == 0) {
                pointValue = num;
                System.out.println(" ");
                System.out.println("Your point value is " + pointValue);
                System.out.println(" ");
                win = rollWithPoint(pointValue);

                if (win) {
                    total = wonGame(bet, total);
                    wins++;
                    numOfGames++;
                    System.out.println("Wins: " + wins + " Number of games: " + numOfGames);
                } else if (!win) {
                    total = lostGame(bet, total);
                    numOfGames++;
                    System.out.println("Wins: " + wins + " Number of games: " + numOfGames);
                }
            } else if (num == 7 || num == 11) {
                total = wonGame(bet, total);
                wins++;
                numOfGames++;
                System.out.println("Wins: " + wins + " Number of games: " + numOfGames);
            } else {
                total = lostGame(bet, total);
                numOfGames++;
                System.out.println("Wins: " + wins + " Number of games: " + numOfGames);
            }

            if (total <= 9) {
                break;
            }

            System.out.println("Keep playing (y/Y or n/N)? ");
            String again = in.nextLine();

            if (again.equalsIgnoreCase("y")) {
                playAgain = true;
            } else if (again.equalsIgnoreCase("n")) {
                playAgain = false;
                break;
            } else {
                System.out.println("Invalid character input, try again:");
            }
        }// end of loop

        gameOver(wins, numOfGames);

    } // END of main

    public static int rollDice() {

        int dice1, dice2, total;
        dice1 = rand.nextInt(6) + 1;
        dice2 = rand.nextInt(6) + 1;
        total = dice1 + dice2;
        System.out.print("Your roll: ");
        System.out.print("Dice1: " + dice1);
        System.out.print(", Dice2: " + dice2);
        System.out.println("; Roll Value: " + total);
        return total;

    } // END of rollDice

    public static boolean rollWithPoint(int point) {

        int total = rollDice();
        boolean winner = false;
        while (total != 7 && winner == false) {
            total = rollDice();
            if (total == point) {
                winner = true;
            } else {
                winner = false;
            }
        }
        return winner;
    } // END of rollWithPoint

    public static int lostGame(int bet, int total) {

        System.out.println("Oh, I'm sorry, you lost.");
        System.out.println(" ");
        total = total - bet;
        System.out.println("Your current balance: $" + total);
        System.out.println(" ");
        return total;

    } // END of lostGame

    public static int wonGame(int bet, int total) {

        System.out.println("A winner!");
        System.out.println(" ");
        total = total + bet;
        System.out.println("Your current balance: $" + total);
        System.out.println(" ");
        return total;

    } // END of wonGame

    public static void gameOver(double win, double tot) {

        double winPercent = (win / tot) * 100;
        System.out.println(" ");
        System.out.println("Based on your play, the probability of winning is " + String.format("%.2f", winPercent) + "%.");
        System.out.println(" ");
        System.out.println("Seems you lost your shirt; better luck next time.");
        System.out.println("Have a nice day! Hope to see you soon!");

    } // END of gameOver

} // END of GameOfCraps

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总结

通过以上修改，可以解决游戏循环中断时可能出现的异常，并确保游戏在玩家选择退出或资金不足时能够正常结束。同时，修正了概率输出的格式，使其更加清晰易懂。希望本文能够帮助Java初学者更好地理解和掌握循环控制和字符串格式化的相关知识。

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