java - java 黑 jack

Question

我正在尝试在 Eclipse 中编写一个黑 jack 程序，但当该程序处理 Ace 时遇到问题。我询问用户是否希望 A 值 1 或 11。确实如此，但当我输入值时，它会给出错误消息

"Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0
    at java.lang.String.charAt(Unknown Source)
    at PlayBlackJack.main(PlayBlackJack.java:72)"

有人可以帮忙吗？我有一个单独的类，如果生成的随机卡是 ace，则返回值 11。这是代码的一部分

更新:它将 Ace 的值添加到用户的总值中。但在发完 A 并用户选择一个值后，无论总数是多少，它都会停止用户的回合并转到庄家。我该如何纠正这个问题？我遇到的另一个问题是，在用户对想要另一张卡说“不”之后，它会转到经销商并且工作正常，但是当询问用户是否想再次玩时，它会进入无限循环并开始抛出出随机卡。我该如何纠正这个问题？

    import java.util.Scanner;

公共(public)类 PlayBlackJack {

public final static int MAXCARDS=52;
//declaring the constant maxcards to be 52
//since there are 52 cards in the deck
public static void main(String[] args) {
    Scanner kbd=new Scanner (System.in);


    String printRules;
    //check to see if the user wants to see the rules or not
    String more;
    //variable used to see if the user would like to play the game
    String next;
    //variable used to see if the user would like another card
    int dealerTotal, userTotal;
    //keeps track of the user's total and the dealer's total
    int wins=0, losses=0;
    //variables used to keep track of the user's wins and losses
    int card = 0;

    System.out.println("                Welcome to Black Jack!");
    System.out.println("Would you like to see the rules? Type yes or no");
    //If yes, rules printed, if no, rules not printed
    printRules=kbd.nextLine();
    printRules=printRules.toUpperCase();
    if (printRules.charAt(0)=='Y')
    {
        (print rules)
        System.out.println("Now lets play!\n\n\n");

    }


        System.out.println("Would you like to play a game of Black Jack?");
        more=kbd.nextLine();
        more=more.toUpperCase();

        next="Yes";
        while (!more.isEmpty() && more.charAt(0)=='Y')
        {
            System.out.println("The game begins with this your first card:");
            userTotal=0;
            dealerTotal=0;


            while (!next.isEmpty() && next.charAt(0)=='Y')
            {
                card=PickACard.findCardValue();



                if (card==11)

                {
                    System.out.println("Would you like the Ace to be a 1 or 11?");
                    int aceValue=kbd.nextInt();

                        while (aceValue!=1 && aceValue!=11)
                        {
                            System.out.println("You did not enter a 1 or 11");
                            aceValue=kbd.nextInt();
                        }
                    card=aceValue;

                }

                userTotal=userTotal+card;

                System.out.println("You're total is " +userTotal);


                if (userTotal>21)
                {
                    System.out.println("Sorry, You lose");
                    losses++;
                    System.out.println("Would you like to play again?");
                    next="No";
                    more=kbd.nextLine();
                    more=more.toUpperCase();

                }
                else 
                {
                System.out.println("Would you like another card?");
                next=kbd.nextLine();
                next=next.toUpperCase();
                }

            }


            while (dealerTotal<=userTotal && userTotal<21)
            {
                System.out.println("Now it's the dealer's turn");
                int card1=0;
            card1=PickACard.findCardValue();

            if (card1==11)
            {       
                int aceValue1;

                        if (dealerTotal+11>21)
                        {
                            aceValue1=1;
                        }
                        else
                        {
                            aceValue1=11;
                        }
                    card1=aceValue1;

            }

            dealerTotal=dealerTotal+card1;
            System.out.println("The dealer's total is "+dealerTotal);


            if (dealerTotal==userTotal && userTotal<21)
            {
                losses++;
                System.out.println("Sorry, you lose. Would you like to play again?");
                more=kbd.nextLine();
                more=more.toUpperCase();

            }

            if (dealerTotal>21)
                {
                    wins++;
                    System.out.println("You Win! Would you like to play again?");
                    more=kbd.nextLine();
                    more=more.toUpperCase();

                }
                /*else
                {
                    losses++;
                    System.out.println("You lose. Would you like to play again?");
                    more=kbd.nextLine();
                    more=more.toUpperCase();

                }*/
            }


        }



        System.out.println("You won "+wins+" game(s) and lost "+losses+" game(s)");
        kbd.close();

}

}

Answer 1

我认为因为您使用 kbd.nextInt() 来获取 Ace 值，所以缓冲区中会留下一个新行字符，因此当循环进行时 kbd.nextLine () 返回新行字符，而不是可能导致 more.charAt(0) 出现问题的 Y，您可能需要添加额外的 kbd.nextLine(); 删除换行符。另外，正如 Elliot Frisch 指出的那样，您应该检查 while 控制语句中的字符串是否为空。

while(!more.isEmpty() && more.charAt(0) == 'y')
{
}

我猜 next.charAt(0) 显示了错误。您可以尝试在询问您是否想要另一个游戏之前执行 kbd.nextLine(); 并检查 next 是否不为空。

 while(!next.isEmpty() && more.charAt(0) == 'y')
    {
    }

试试这个

System.out.println("Sorry, You lose");
losses++;
System.out.println("Would you like to play again?");
next="No";
kbd.nextLine(); // to flush out new line character
more=kbd.nextLine();
more=more.toUpperCase();

您还可以使用 nextLine() 并将其解析为 int，这样可以避免换行符问题。

aceValue = Integer.parseInt(kbd.nextLine());