Do/while循环执行不正确

Question

我确定我缺少一些简单的东西，但我无法让我的while while循环正确执行。我希望它能够第一次运行并持续到用户输入q。它目前执行一次，然后循环备份以询问要访问的帐户，然后什么都不做。任何帮助或指引我在正确的方向，所以我可以修复它将不胜感激。

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

你必须确保你读一开始这两个选项; accountChoice和accountActivity。您的代码有一个问题是缺少{和}的用法。

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")); 
    } 
} 

Answer 2

你缺少一个大括号对这一说法后：

if(accountChoice.equalsIgnoreCase("regular")) 

...及本声明：

if (accountActivity.equalsIgnoreCase("withdraw")) 

为Java（和C的默认行为，和C++）仅在执行if，for或while语句后执行下一个行，如果大括号是省略。

当你完成后，你的说法应该是这样的：

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 
}