找到一個銀行賬戶的總數

Question

我是一個學生剛剛完成我的第一年學習Java，並有一個問題「創建一個方法，返回在銀行總資金？」在考試中。我已經包括下面的類。我得到了大部分正確的方法，包括addAccount（），getBalance（），withdraw（）等，但不確定這個答案是什麼。這可能比我想象的簡單並且更簡單（我必須使用for循環或某種類型的兩個循環），但只是爲了澄清合計總和的正確方法。這也出現在一家雜貨店的C＃作業中，客戶從不同的產品（例如水果蔬菜等）購買了貨物，並且必須計算總計。

預先感謝您...

保羅

代碼： 超類：

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

    /** 
     Constructs a bank account with a zero balance. 
    */ 
    public BankAccount() 
    { 
     balance = 0; 
    } 

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

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

    /** 
     Withdraws money from the bank account. 
     @param amount the amount to withdraw 
    */ 
    public void withdraw(double amount) 
    { 
     if (balance >= amount) 
     { 
     balance = balance - amount; 
     } 
     else 
     { 
      System.out.println("Withdrawal error: insufficent funds"); 
     } 
    } 

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

    /** 
     Transfers money from the bank account to another account 
     @param amount the amount to transfer 
     @param other the other account 
    */ 
    public void transfer(double amount, BankAccount other) 
    { 
     withdraw(amount); 
     other.deposit(amount); 
    } 

    public String toString() 
    { 
     return "Your Balance: "+ balance; 
    } 
} 

子類的支票帳戶：

/** 
    A checking account that charges transaction fees. 
*/ 
public class CheckingAccount extends BankAccount 
{ 
    private int transactionCount; 
    private int transaction; 

    private static final int FREE_TRANSACTIONS = 0; 
    private static final double TRANSACTION_FEE = 2.0; 

    /** 
     Constructs a checking account with a given balance. 
     @param initialBalance the initial balance 
    */ 
    public CheckingAccount(double initialBalance) 
    { 
     // Construct superclass 
     super(initialBalance); 

     // Initialize transaction count 
     transactionCount = 0; 
    } 

    public void deposit(double amount) 
    { 
     transactionCount++; 
     // Now add amount to balance 
     super.deposit(amount); 
    } 

    public void withdraw(double amount) 
    { 
     transactionCount++; 
     // Now subtract amount from balance 
     super.withdraw(amount); 
    } 

    /** 
     Deducts the accumulated fees and resets the 
     transaction count. 
    */ 
    public void deductFees() 
    { 
     if (transactionCount > FREE_TRANSACTIONS) 
     { 
     double fees = TRANSACTION_FEE * 
       (transactionCount - FREE_TRANSACTIONS); 
     super.withdraw(fees); 
     } 
     transaction = transactionCount; 
    } 

    public String toString() 
    { 

     return super.toString() + "\t Your Transactions: "+ transaction; 
    } 

} 

子類儲蓄帳戶：

/** 
    An account that earns interest at a fixed rate. 
*/ 
public class SavingsAccount extends BankAccount 
{ 
    private double interestRate; 

    /** 
     Constructs a bank account with a given interest rate. 
     @param rate the interest rate 
    */ 
    public SavingsAccount(double rate) 
    { 
     interestRate = rate; 
    } 

    /** 
     Constructs a bank account with a given interest rate. 
     @param rate the interest rate 
    */ 
    public SavingsAccount(double rate, double initBalance) 
    { 
     super(initBalance); 
     interestRate = rate; 
    } 

    /** 
     Adds the earned interest to the account balance. 
    */ 
    public void addInterest() 
    { 
     double interest = getBalance() * interestRate + 100; 
     deposit(interest); 
    } 

     public String toString() 
    { 

     return super.toString() + "\t Your Interest rate: "+ interestRate; 
    } 

} 

Answer 1

你說得對。

如果您擁有BankAccounts或其子類的集合，那麼可以在for循環中將它們簡單地相加。

可以說，你有這樣的事情（我假設有包含一個函數，給了我所有賬戶以某種方式銀行對象）：

Collection<BankAccount> accounts = Bank.getAccounts(); 
Double sum = 0.0; 
for (BankAccount account : accounts) { 
    sum += account.getBalance(); 
} 

Answer 2

您正在思考一個循環的正確軌道。只需總結餘額。

public static double totalBalance(Collection<BankAccount> accounts){ 
    double sum = 0.0; 
    for(BankAccount b : accounts){ 
     sum += b.getBalance(); 
    } 
    return sum; 
}