Question

好的伙计们，我在这些代码和一些逻辑上遇到了这些构造函数的问题。我完成了大部分工作，只是对如何完成此操作感到困惑。

这是我的主要代码。（它可能有点草率，但它“足够好”）

public class Accountdrv {
  public static void main (String[] args) {
    Account account = new Account(1122, 20000, 4.5);

    account.withdraw(2500);
    account.deposit(3000);
    System.out.println("Balance is " + account.getBalance());
    System.out.println("Monthly interest is " +
      account.getMonthlyInterest());
    System.out.println("This account was created at " +
      account.getDateCreated());
  }
}

class Account {
  private int id;
  private double balance;
  private double annualInterestRate;
  private java.util.Date dateCreated;

  public Account() {
    dateCreated = new java.util.Date();
  }

  public Account(int id, double balance, double annualInterestRate) {
    this.id = id;
    this.balance = balance;
    this.annualInterestRate = annualInterestRate;
    dateCreated = new java.util.Date();
  }

  public int getId() {
    return this.id;
  }

  public double getBalance() {
    return balance;
  }

  public double getAnnualInterestRate() {
    return annualInterestRate;
  }

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

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

  public void setAnnualInterestRate(double annualInterestRate) {
    this.annualInterestRate = annualInterestRate;
  }

  public double getMonthlyInterest() {
    return balance * (annualInterestRate / 1200);
  }

  public java.util.Date getDateCreated() {
    return dateCreated;
  }

  public void withdraw(double amount) {
    balance -= amount;
  }

  public void deposit(double amount) {
    balance += amount;
  }
}

现在，我想创建一个储蓄和支票帐户。我需要帮助我需要为构造函数添加的内容，我在注释中添加了我知道的部分，但我对此缺失感到困惑。

节约：

class Savings extends Account{
//need to create a constructor
  public Savings(int id, double balance, double annualInterestRate) {
//need to invoke the constructor for Account
  super(id, balance, annualInterestRate);
 }

// need to override the withdraw method in Account
public void withdraw(double amount) {
    // place logic to prevent the account from being overdrawn
    // that is do not allow a negative balance
  }
}

Answer 1

你只需要检查id的数量＆lt;平衡或者你拥有的任何逻辑（例如：你想要的）帐户中存在一些阈值金额。）

此外，我建议您查看同步方法，因为您应该同步访问给定用户的帐户，以确保在调用撤销功能时...同一用户帐户的另一个撤销必须等待......否则它会导致问题...我会留给你弄清楚。

public void withdraw(double amount) {
// place logic to prevent the account from being overdrawn
// that is do not allow a negative balance

     if(balance < amount)
     {
        // print error message or do something
     }
     else
     {
        // withdraw the money
        balance -= amount;
        // print message or do something
     }
}

Answer 2

super()在Savings案例Account中调用超类的构造函数。

子类的构造函数

2 个答案: