java - 全局变量无法识别用户输入的数字

Question

import java.util.Scanner;




public class Blackjack {

    class Commands {
        static final String yes = "yes";
        static final String no = "no";
    }

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        //Opponent player2 = new Opponent();
        double AiCard1 = 0;
        double AiCard2 = 0;
        double AiCard3 = 0;
        double AiTotalcard3 = AiCard1 + AiCard2 + AiCard3;
        double card1 = 0;
        double card2 = 0;
        double card3 = 0;
        double card4 = 0;
        double total2 = card1 + card2 + card3 + card4;
        double total = card1 + card2 + card3;



        System.out.println("Hello and Welcome to my custom version of blackjack!");
        System.out.println("You will start off with $300");
        System.out.println();
        System.out.println("Do you want to read the rules before playing?");
        System.out.print("Press 1 if yes, press 2 for no");


            int choice = input.nextInt();
            switch (choice) {
            case 1: 
                System.out.println("You have 4 cards to get as close to 21 as possible.  Whoever is closest to 21 wins");
                break;
            default:
                break;
        }




        int balance = 300;

        System.out.println("Your bank balance is $" + balance);
        //user places a bet
        System.out.println("Place a bet");

        int bet = input.nextInt();
        System.out.println("You placed a bet of " + bet);

        //this is the AI 
        AiCard1 = Math.random() * 12 + 1;
        AiCard1 = Math.round(AiCard1);
        AiCard2 = Math.random() + 12 + 1;
        AiCard2 = Math.round(AiCard2);
        double AiTotal2cards = AiCard1 + AiCard2;
        if(AiTotal2cards < 15) {
            AiCard3 = Math.random() * 12 + 1;
            AiCard3 = Math.round(AiCard3);
            AiTotalcard3 = AiCard1 + AiCard2 + AiCard3;
        }



        card1 = Math.random() * 12 + 1;
        card1 = Math.round(card1);
        System.out.println("Your first card was a " + card1);
        System.out.println();

        card2 = Math.random() * 10 + 1;
        card2 = Math.round(card2);

        System.out.println("Your second card was a " + card2);
        System.out.println();

        System.out.println("Your cards add up to " + (card1 + card2));
        System.out.println("Do you want to add another card?");
        String answer = input.next();
        here:
        if(answer.equals(Commands.yes)) {

            card3 = Math.random() * 12 + 1;
            card3 = Math.round(card3);
            System.out.println("Your third card was a " + card3);
            System.out.println("Your cards add up to " + (card1 + card2 + card3));
            total = card1 + card2 + card3;

            if(total > 21) {
                System.out.println("You lose");
                break here;
            }
            System.out.println("Do you want to add another card?");


            String answer1 = input.next();
            if(answer1.equals(Commands.no)){
                break here;
            }
            if(answer1.equals(Commands.yes)) {

                card4 = Math.random() * 12 + 1;
                card4 = Math.round(card4);
                System.out.println("Your fourth card was a " + card4);
                System.out.println("Your cards add up to " + (card1 + card2 + card3 + card4));
                total2 = card1 + card2 + card3 + card4;

                if(total2 > 21) {
                    System.out.println("You lose");
                    break here;
                }
                break here;
            }
        }
        System.out.println("Your total cards were " + total2);
        System.out.println("AI total cards were " + AiTotalcard3);
        input.close();

    }
}

当您运行该程序时，我希望顶部的变量会在用户运行该程序时将新数字保存到其中。有没有更好的方法来执行此操作，因为控制台输出的总数始终为 0。

Answer 1

首先让我们看看AiTotalcard3 :

它不应该总是为此输出 0，更准确地说，它会在 AiCard1 + AiCard2 >= 15 的情况下输出 0。 ，这可能经常发生。

如果您跟踪实际代码，这是有意义的。首先发生的是那些初始化器:

double AiCard1 = 0;
double AiCard2 = 0;
double AiCard3 = 0;
double AiTotalcard3 = AiCard1 + AiCard2 + AiCard3;

所以 AiTotalcard3最初设置为 0。它将保持为 0，直到您更改它，更改发生在此处:

AiCard1 = Math.random() * 12 + 1;
AiCard1 = Math.round(AiCard1);
AiCard2 = Math.random() + 12 + 1;
AiCard2 = Math.round(AiCard2);
double AiTotal2cards = AiCard1 + AiCard2;
if(AiTotal2cards < 15) {
    AiCard3 = Math.random() * 12 + 1;
    AiCard3 = Math.round(AiCard3);
    AiTotalcard3 = AiCard1 + AiCard2 + AiCard3;
}

但这只有在前两张牌加起来小于 15 时才会发生。之后你永远不会碰 AiTotalcard3再次。

您的逻辑可以大大全面简化，而且使用 int 也更有意义而不是 double对于卡片，但忽略所有这些并坚持您当前的风格，您可以通过确保设置所有路径来解决此问题 AiTotalcard3 ，例如(同样不是最干净的逻辑，只是坚持你的模式):

if(AiTotal2cards < 15) {
    AiCard3 = Math.random() * 12 + 1;
    AiCard3 = Math.round(AiCard3);
    AiTotalcard3 = AiCard1 + AiCard2 + AiCard3;
} else {
    AiTotalcard3 = AiCard1 + AiCard2; // be sure to always set it
}

现在，考虑到所有这些，您遇到了与 total2 类似的问题: 并非所有执行路径都设置了 total2 的值. 如果你将它补到第 4 张牌，但在此之前你永远不会改变它的初始值 0。所以你将不得不用细齿梳理它。

您的一个基本问题是出于某种原因，您在前两张牌和所有牌上到处使用不同的变量。如果你只使用一个 aiTotal和 total边走边累积卡片总数，可以避免大多数此类问题。