Do/while 循环没有正确执行

Question

我确定我遗漏了一些简单的东西，但我无法让我的 do while 循环正确执行。我希望它第一次运行并继续运行，直到用户输入 q。它当前执行一次，然后循环回来询问要访问的帐户，然后什么也不做。任何帮助或指出我正确的方向以便我可以解决它将不胜感激。

public class Crawford_Driver
{

    public static void main(String[] args)
    {
        Scanner keyboard = new Scanner(System.in);
        double input1;
        String accountChoice;
        String accountActivity;
        RegularAccount regAcct = new RegularAccount(0, .5);
        SavingsAccount savAcct = new SavingsAccount(0, .5);


        do{
            System.out.println("What account would you like to access(regular or savings)?" );
            accountChoice = keyboard.nextLine();

            if(accountChoice.equalsIgnoreCase("regular"))

                System.out.println("What action do you wish to perform(deposit, withdraw or monthly process)? ");
            accountActivity = keyboard.nextLine();

            if (accountActivity.equalsIgnoreCase("deposit"))
                {
                    System.out.println("How much would you like to deposit?");
                    input1= keyboard.nextDouble();
                    regAcct.deposit(input1);
                    System.out.println("Your balance is " + regAcct.getBalance() );
                }
            else if (accountActivity.equalsIgnoreCase("withdraw"))
                {
                    System.out.println("How much would you like to withdraw?");
                    input1= keyboard.nextDouble();
                    regAcct.withdraw(input1);
                    System.out.println("Your balance is "+ regAcct.getBalance());
                }
            else if (accountActivity.equalsIgnoreCase("monthly process"))
                {
                    regAcct.monthlyProcess();
                }
            else {
                if (accountChoice.equalsIgnoreCase("savings"))

                    if (accountActivity.equalsIgnoreCase("deposit"))
                        {
                            System.out.println("How much would you like to deposit?");
                            input1= keyboard.nextDouble();
                            savAcct.deposit(input1);
                            System.out.println("Your balance is " + savAcct.getBalance() );
                        }

                if (accountActivity.equalsIgnoreCase("withdraw"))

                    System.out.println("How much would you like to withdraw?");
                input1= keyboard.nextDouble();
                savAcct.withdraw(input1);
                System.out.println("Your balance is "+ savAcct.getBalance());

            }
        }while (!accountChoice.equalsIgnoreCase("Q"));

    }
}

Answer 1

您在此语句之后缺少一组花括号：

if(accountChoice.equalsIgnoreCase("regular"))

...还有这句话：

 if (accountActivity.equalsIgnoreCase("withdraw"))

如果省略大括号，Java（以及 C 和 C++）的默认行为是仅执行 if、for 或 while 语句之后的 下一个 行。

完成后，您的语句应如下所示：

if(accountChoice.equalsIgnoreCase("regular")) {
    System.out.println("What action do you wish to perform(deposit, withdraw or monthly process)? ");
    accountActivity = keyboard.nextLine();
    // Rest of code that concerns activity with a "regular" account
}

Answer 2

您必须确保一开始就阅读了这两个选项； accountChoice 和 accountActivity。您的代码的一个问题是缺少{ 和} 的使用。

所以它会像......

do { // do below first before checking the while condition
    if(accountChoice.equalsIgnoreCase("regular")) 
    {
        // do your work.
    } else if (accountChoice.equalsIgnoreCase("savings")) 
    {
        // do the rest
    }
} while (!accountChoice.equalsIgnoreCase("Q"));

下面是修改后的代码。

public class Crawford_Driver
{

    public static void main(String[] args)
    {
        Scanner keyboard = new Scanner(System.in);
        double input1;
        String accountChoice;
        String accountActivity;
        RegularAccount regAcct = new RegularAccount(0, .5);
        SavingsAccount savAcct = new SavingsAccount(0, .5);


        do {
            System.out.println("What account would you like to access(regular or savings)?" );
            accountChoice = keyboard.nextLine();

            System.out.println("What action do you wish to perform(deposit, withdraw or monthly process)? ");
            accountActivity = keyboard.nextLine();


            if(accountChoice.equalsIgnoreCase("regular")) { // LINE moved and BRACKET MISSING

                if (accountActivity.equalsIgnoreCase("deposit"))
                {
                    System.out.println("How much would you like to deposit?");
                    input1= keyboard.nextDouble();
                    regAcct.deposit(input1);
                    System.out.println("Your balance is " + regAcct.getBalance() );
                }
                else if (accountActivity.equalsIgnoreCase("withdraw"))
                {
                    System.out.println("How much would you like to withdraw?");
                    input1= keyboard.nextDouble();
                    regAcct.withdraw(input1);
                    System.out.println("Your balance is "+ regAcct.getBalance());
                }
                else if (accountActivity.equalsIgnoreCase("monthly process"))
                {
                    regAcct.monthlyProcess();
                }
            } 
            else if (accountChoice.equalsIgnoreCase("savings")) 
            { // line changed &  BRACKET MISSING

                if (accountActivity.equalsIgnoreCase("deposit"))
                {
                    System.out.println("How much would you like to deposit?");
                    input1= keyboard.nextDouble();
                    savAcct.deposit(input1);
                    System.out.println("Your balance is " + savAcct.getBalance() );
                }
                else if (accountActivity.equalsIgnoreCase("withdraw")) 
                { // bracket missing

                    System.out.println("How much would you like to withdraw?");
                    input1= keyboard.nextDouble();
                    savAcct.withdraw(input1);
                    System.out.println("Your balance is "+ savAcct.getBalance());
               }
           }
       } while (!accountChoice.equalsIgnoreCase("Q"));
   }
}