Java Math.max用于银行账户交易

Question

因此，我遇到了这个问题，我一直在努力实现的目标是扣除银行账户中每笔交易的费用，这笔交易超过了分配数量的免费交易。到目前为止，我已经掌握了一切以计算交易，但我们应该与Math.max合作，以便在您结束免费交易时，费用开始从余额中扣除帐户。我在我的deductMonthlyCharge方法中使用Math.max。我想我知道如何用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也不是很熟悉。所以，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

我想你想要的东西，这样的（这超过允许量假定为$ 1.00费每笔交易）：

public double deductMonthlyCharge() 
{ 
    int transCount = Math.max(transactionCount, freeTransactions); 
    double fee = 1.00 * (transCount - freeTransactions); 
    return fee; 
} 

如果客户没有走在他们允许自由交易的数量，然后(transCount - freeTransactions)将为0，因此不收取任何费用。

这段代码对自己来说太聪明了，但我认为这是偏心要求（不要使用if语句，用max来代替）。

更清晰的（但等效）将是：

public double deductMonthlyCharge() 
{ 
    if (transactionCount > freeTransactions) { 
     return 1.00 * (transactionCount - freeTransactions); 
    } 
    return 0.0; 
} 

Answer 2

max(double, double)返回grouter double值。如果你想返回的更大的价值只是改变

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

到

return Math.max(transactionCount, freeTransactions); 

。

双打，就像所有的基本类型都没有像对象一样的引用。您需要保存返回的值，如double foo = functionThatReturnPrimitiveDouble()或者像我在上面的示例中那样再次将其返回。