java - 子类不继承所有方法

Question

我有一个名为“Account”的类:

import java.util.Date;

public class Account {

    public int id = 0; //Declare default id as 0
    public double balance = 0; //Declare default balance as 0
    public double annualInterestRate = 0; //Declare default annual interest rate as 0
    public Date dateCreated = new Date(); //Declare date

    //No argument constructor for Account
    public Account() {
    id = 0;
    balance = 0.0;
    annualInterestRate = 0.0;
    }   

    //Constructor that accepts ID, Balance, and Annual Interest Rate
    public Account(int newID, double newBalance, double newAnnualInterestRate) {
    id = newID;
    balance = newBalance;
    annualInterestRate = newAnnualInterestRate;
    }  

    //Get ID
    public int getId() {
        return id;
    }

    //Set ID
    public void setId(int id) {
        this.id = id;
    }

    //Get Balance
    public double getBalance() {
        return balance;
    }

    //Set Balance
    public void setBalance(double balance) {
        this.balance = balance;
    }

    //Get Annual Interest Rate
    public double getAnnualInterestRate() {
        return annualInterestRate;
    }

    //Set Annual Interest Rate
    public void setAnnualInterestRate(double annualInterestRate) {
        this.annualInterestRate = annualInterestRate;
    }

    //Get Date Created
    public Date getDateCreated() {
        return dateCreated;
    }

    //Withdraw method
    double withdraw(double amount) {
    return balance -= amount;
    }

    //Deposit method 
    double deposit(double amount) {
    return balance += amount;
    }

    //Interest rate method
    double getMonthlyInterestRate() {
    return (balance * annualInterestRate) / 12;
   }

} //End Account class 

然后我创建了两个不同的子类“PreferredCustomer”和“CommercialCustomer”。这两个类应该继承主“Account”类的所有方法(存款、取款、月利率和所有getters和setters)。与子类的唯一区别是它们有一个预先确定的利率。

public class PreferredCustomer extends Account {

    public double annualInterestRate;

    public PreferredCustomer() {
    }

    public PreferredCustomer(int id, double balance) {
    super();
    this.annualInterestRate = .04;
    }

} //end PreferredCustomer Class

我感觉目前的设置方式不准确。测试时，withdraw 和 deposit 方法有效，但尽管输入了 20,000 美元的起始余额，它仍然将起始余额设置为 0 美元并且不计算利率。

我正在测试这个类:

public class TestingAccountClass {

public static void main(String[] args) {

    //Create accounts
    CommercialCustomer myCommercialCustomerAccount = new CommercialCustomer(1124, 
          20000.00);

   //Invoking deposit method from account class
   myCommercialCustomerAccount.deposit(3000.00);

   //Display account balance, monthly interest, and date created
   System.out.println("\n\n----Commercial Account---");
   System.out.println("Account Created On: "
       + myCommercialCustomerAccount.getDateCreated());
   System.out.printf("Balance: $%.2f", myCommercialCustomerAccount.getBalance());
   System.out.printf("\nMonthly Interest: $%.2f"
       ,myCommercialCustomerAccount.getMonthlyInterestRate());

当以这种方式测试类时，存款方法有效，但帐户类中的任何其他方法(除了提款)似乎都无效。任何意见，将不胜感激。谢谢你!

Answer 1

你这样做:

CommercialCustomer myCommercialCustomerAccount = new CommercialCustomer(1124, 20000.00);

但是，

public PreferredCustomer(int id, double balance) {
    super();
    this.annualInterestRate = .04;
}

您无需对天平进行任何操作!

您或许可以将其更改为:

public PreferredCustomer(int id, double balance) {
    super();
    this.balance = balance;
    this.annualInterestRate = .04;
}

但是您将向 balance 写入两次。

此外，拥有两个同名变量(基础变量与子变量)是个坏主意 -> annualInterestRate。

编辑 ---------------------------------------- 编辑

我会推荐这样的东西:

public Account() {
    this(0, 0d, 0d);
}  

public Account(int id, double balance, double interestRate) {
    this.id = id;
    this.balance = balance;
    this.annualInterestRate = interestRate;
}   

public PreferredCustomer(int id, double balance) {
    super(id, balance, 0.04d);
}

EDIT2 ---------------------------------------- EDIT2

这是错误的。您正在进行整数除法。

return (balance * annualInterestRate) / 12;

更改为:

return (balance * annualInterestRate) / 12d;

或者这个:

return (balance * annualInterestRate) / 12.0;