用于银行帐户交易的 Java Math.max

Question

所以，我一直在解决这个问题，目标是为银行帐户中超过分配的免费交易数量的每笔交易扣除费用。到目前为止，我已经准备好了计算交易的一切，但我们应该与 Math.max 合作来实现这一点，这样当您超过免费交易金额时，费用就会开始从余额中扣除帐户。我在 deductMonthlyCharge 方法中使用 Math.max 。我想我知道如何使用 if 和 else 语句来做到这一点，但我们不允许在这里使用它们，而且我对 Math.max 不是很熟悉。因此，如果有人能指出我正确的方向来解决这个问题，那就太好了。谢谢。

/**
A bank account has a balance that can be changed by 
deposits and withdrawals.
*/
public class BankAccount
{  
    private double balance;
private double fee;
private double freeTransactions;
private double transactionCount;

/**
   Constructs a bank account with a zero balance
*/
public BankAccount()
{   
  balance = 0;
    fee = 5;
    freeTransactions = 5;
    transactionCount = 0;
}

/**
  Constructs a bank account with a given balance
   @param initialBalance the initial balance
*/
public BankAccount(double initialBalance)
{   
  balance = initialBalance;
    transactionCount = 0;
}

public static void main(String [ ] args)
{
    BankAccount newTransaction = new BankAccount();
    newTransaction.deposit(30);
    newTransaction.withdraw(5);
    newTransaction.deposit(20);
    newTransaction.deposit(5);
    newTransaction.withdraw(5);
    newTransaction.deposit(10);
    System.out.println(newTransaction.getBalance());
    System.out.println(newTransaction.deductMonthlyCharge());

}
public void setTransFee(double amount)
{
    balance = amount+(balance-fee);
    balance = balance;

}

public void setNumFreeTrans(double amount)
{
    amount = freeTransactions;
}

/**
   Deposits money into the bank account.
   @param amount the amount to deposit
*/
public void deposit(double amount)
{  
  double newBalance = balance + amount;
  balance = newBalance;
    transactionCount++;
}

/**
  Withdraws money from the bank account.
  @param amount the amount to withdraw
*/
public void withdraw(double amount)
{   
  double newBalance = balance - amount;
  balance = newBalance;
    transactionCount++;
}

public double deductMonthlyCharge()
{
    Math.max(transactionCount, freeTransactions);
    return transactionCount;
}

 /**
  Gets the current balance of the bank account.
  @return the current balance
*/
public double getBalance()
{   
  return balance;
}
 }

Answer 1

max(double, double) 返回灌浆器 double 值。只需更改

Math.max(transactionCount, freeTransactions);
    return transactionCount;

至

return Math.max(transactionCount, freeTransactions);

如果您希望返回更大的值。

double ，就像所有原始类型一样，没有像对象那样的引用。您需要像 double foo = functionThatReturnPrimitiveDouble() 一样保存返回值，或者像我在上面的示例中那样再次返回它。