java - 返回 toString 方法，不返回我想要的(Java)

Question

我有一个项目，我正在创建一个带有 SavingsAccount 子类的 BankAccount 父类(super class)。一切正常，但我无法返回我特别想要的字符串。

示例:(修剪)

public class BankAccount {
   public static final double MONTHS_IN_YEAR = 12.0;

   private String myCustomerName;
   private double myAccountBalance;
   private double myInterestRate;
   protected int myMonthlyWithdrawCount;
   protected double myMonthlyServiceCharges;

   public BankAccount(final String theNameOfOwner, 
                      final double theInterestRate) {
      myCustomerName = theNameOfOwner;
      myAccountBalance = 0.0;
      myInterestRate = theInterestRate;
      myMonthlyWithdrawCount = 0;
      myMonthlyServiceCharges = 0.0;
   }

   public String toString() {
      String result = "";
      result += String.format("BankAccount[owner: %s, balance: %.2f,",
                               myCustomerName, myAccountBalance);
      result += String.format(" interest rate: %.2f,", myInterestRate);
      result += String.format("\n\t\t  ");
      result += String.format("number of withdrawals this month: %d,",
                               myMonthlyWithdrawCount);
      result += String.format(" service charges for this month: %.2f]",
                               myMonthlyServiceCharges);
      return result;         
   }
}

驱动类将使用 BankAccount 的 toString 方法并打印:

BankAccount[owner: John Doe, balance: 0.00, interest rate: 0.05,
          number of withdrawals this month: 0, service charges for this                month: 0.00] 

(这对这个父类(super class)来说是完美的)

然而，这里出现了子类 SavingsAccount

public class SavingsAccount extends BankAccount {
   public static final double SAVINGS_THRESHOLD = 25.0;

   private boolean myStatusIsActive;

   public SavingsAccount(final String theNameOfOwner, 
                         final double theInterestRate) {
      super(theNameOfOwner, theInterestRate);
      myStatusIsActive = false;
      if (super.getBalance() >= SAVINGS_THRESHOLD) {
         myStatusIsActive = true;
      }
   }

   public String toString() {
      String result = "";
      result += "SavingsAccount";
      result += super.toString();
      return result;
   }
}

调用SavingsAccount的toString方法时，打印:

SavingsAccountBankAccount[所有者:Dan Doe，余额:0.00，利率:0.05， 本月取款笔数:0，本月手续费:0.00】

(我不希望包含 BankAccount，我只希望它打印“SavingsAccount” header ，然后直接转到 [owner : Dan Doe,"

我试过让它首先返回“SavingsAccount”，它正确地返回了，但是当调用 super.toString() 时，它最终也返回了 BankAccount header 我不想要。

关于如何解决这个问题有什么想法吗？

Answer 1

我能想到的几个选项:

1. 将“BankAccount”替换为“SavingsAccount”，而不仅仅是附加它:

   @Override
   public String toString() {
       return super.toString().replaceFirst("BankAccount", "SavingsAccount");
   }
   

2. 将详细信息部分移到它自己的方法中，并使用适当的 header 从每个 toString() 调用它:

   // BankAccount.java
   @Override
   public String toString() {
       return "BankAccount" + getDetailsString();
   }
   
   protected String getDetailsString() {
       String result = String.format("[owner: %s, balance: %.2f,",
               myCustomerName, myAccountBalance);
       // ...
       return result;
   }
   
   // SavingsAccount.java
   @Override
   public String toString() {
       return "SavingsAccount" + getDetailsString();
   }
   

3. 获取父类(super class)中的运行时类名，这样就不需要完全覆盖它:

   @Override
   public String toString() {
       String result = String.format("%s[owner: %s, balance: %.2f,",
               getClass().getSimpleName(), myCustomerName, myAccountBalance);
       // ...
       return result;
   }