Java中的抽象類獲取器和設置器

Question

所以，解釋一下我的代碼->

我有一個Employee類型的抽象類，它有自己的字段，例如名稱。

然后，我有了從Employee擴展的Admin，Sales和Manager類。 這些都有各自的字段，例如admin的fixedBonus，Sales的percentBonus和經理的雇員數組列表。

然后，我有一個驅動程序類，其中包含一個EmployeeArray，因此它包含Admins，Sales和Managers。

我的問題出現在Arraylist元素上。 假設我從ArrayList中獲得了Admin類的雇員，並嘗試使用getter getFixedBonus（）到達其fixedBonus字段，我簡直不能。 如何做到這一點，這樣我就可以使用類特定的getter和setter，而不僅僅是繼承的？ 這是我的代碼的副本，出現問題的地方。 具體來說，問題在於switch語句的情況5和情況6。

private Employee editAnEmployee(Employee emp) {
    boolean exit = false;
    boolean validChoice = false;
    int choice = 0;
    Boolean sure = false; // used in the switch statement
    String newName;
    double newValue;
    Employee admin = new AdminWorker("0", "0", 0, 0, 0); // these are used
    Employee sales = new SalesWorker("0", "0", 0, 0, 0, 0); // to check the
    Employee manager = new Manager("0", "0", 0, 0); // class of the
                                                    // employee
                                                    // being sent
                                                    // in, to edit
                                                    // the fields
                                                    // the employee
                                                    // may hold
    do {
        do {
            validChoice = true;
            emp.toString();
            StdOut.println("Which field would you like to edit?");
            StdOut.println("1) First Name.");
            StdOut.println("2) last Name.");
            StdOut.println("3) Hourly rate.");
            StdOut.println("4) Hours worked in the last week.");
            if (emp.getClass().equals(admin)) {
                StdOut.println("5) Fixed Bonus.");
            } else if (emp.getClass().equals(sales)) {
                StdOut.println("5) Percentage bonus on sales.");
                StdOut.println("6) Value of sales made in the last week.");
            } else if (emp.getClass().equals(manager)) {
                StdOut.println("5) Department.");
            }
            StdOut.println("0) Exit.");
            choice = StdIn.readInt();
            if (choice < 0 || choice > 4) {
                if (emp.getClass().equals(admin) && choice <= 5) {
                    validChoice = true;
                } else if (emp.getClass().equals(sales) && choice <= 6) {
                    validChoice = true;
                } else if (emp.getClass().equals(manager)) {
                    validChoice = true;
                } else {
                    StdOut.println("You entered an invalid number! Try Again...");
                    validChoice = false;
                }
            }
        } while (!validChoice);
        switch (choice) {
        case 0:
            StdOut.println("You are now exiting...");
            exit = true;
            break;
        case 1:
            StdOut.println("The employees first name is: " + emp.getFirstName() + ". What would you like the first name to be now?");
            newName = StdIn.readString();
            StdOut.println("Are you sure you want to change " + emp.getFirstName() + " to " + newName +"?(y/n)");
            sure = ynChoice();
            if(sure) emp.setFirstName(newName);
            break;
        case 2:
            StdOut.println("The employees last name is: " + emp.getLastName() + ". What would you like the last name to be now?");
            newName = StdIn.readString();
            StdOut.println("Are you sure you want to change " + emp.getLastName() + " to " + newName +"?(y/n)");
            sure = ynChoice();
            if(sure) emp.setLastName(newName);
            break;
        case 3:
            StdOut.println("The employees hourly rate is: " + emp.getHourlyRate() + ". What would you like the hourly rate to be now?");
            newValue = StdIn.readDouble();
            StdOut.println("Are you sure you want to change " + emp.getHourlyRate() + " to " + newValue +"?(y/n)");
            sure = ynChoice();
            if(sure) emp.setHourlyRate(newValue);
            break;
        case 4:
            StdOut.println("The employee has worked: " + emp.getHoursWorked() + " hours in the last week. What would you like that to be now?");
            newValue = StdIn.readDouble();
            StdOut.println("Are you sure you want to change " + emp.getHoursWorked() + " to " + newValue +"?(y/n)");
            sure = ynChoice();
            if(sure) emp.setHoursWorked(newValue);
            break;
        case 5:
            if (emp.getClass().equals(admin)) {
                StdOut.println("The employees fixed bonus is: " + emp.getFixedBonus() + ". What would you like that to be now?");
                newValue = StdIn.readDouble();
                StdOut.println("Are you sure you want to change " + emp.getFixedBonus() + " to " + newValue +"?(y/n)");
                sure = ynChoice();
                if(sure) emp.setHoursWorked(newValue);
            } else if (emp.getClass().equals(sales)) {
                StdOut.println("The employees percentage bonus is: " + emp.getPercentageBonus() + ". What would you like that to be now?");
                newValue = StdIn.readDouble();
                StdOut.println("Are you sure you want to change " + emp.getPercentageBonus() + " to " + newValue +"?(y/n)");
                sure = ynChoice();
                if(sure) emp.setHoursWorked(newValue);
            } else if (emp.getClass().equals(manager)) {
                StdOut.println("The employees fixed bonus is: " + emp.getFixedBonus() + ". What would you like that to be now?");
                newValue = StdIn.readDouble();
                StdOut.println("Are you sure you want to change " + emp.getFixedBonus() + " to " + newValue +"?(y/n)");
                sure = ynChoice();
                if(sure) emp.setHoursWorked(newValue);
            }
            break;
        case 6:
            StdOut.println("The employees sales in the last week are: " + emp.getLastWeeksSales() + ". What would you like that to be now?");
            newValue = StdIn.readDouble();
            StdOut.println("Are you sure you want to change " + emp.getLastWeeksSales() + " to " + newValue +"?(y/n)");
            sure = ynChoice();
            if(sure) emp.setHoursWorked(newValue);
            break;
        }
    } while (!exit);
    return emp;
}

Answer 1

我認為instanceof關鍵字在您的情況下可能很有用。

ArrayList<Employee> list; // This is initialized and has Employees

for (Employee person: list) {
    if (person instanceof Admin) {
        int fixedBonus = ((Admin) person).getFixedBonus();

        // Do something here
    }
}

這是否回答你的問題？ （您不需要.getClass（）。equals（），這就是instanceD用於：D的原因）

Answer 2

您應該將getFixedBonus()和getPercentBonus()方法添加到您的員工中，每個方法返回0。然后其他worker類可以覆蓋它們。

實際上，一種更好的技術是使其成為一個interface並使所有類（包括Employee ）都實現該interface 。 然后，他們可以extend一個base類，該base類也實現接口但提供默認值。

public static interface Staff {
  public double getFixedBonus ();
  public double getPercentageBonus ();
  public List<Staff> getMinions();
}

// Base class - no bonus by default.
public static class Worker implements Staff {

  @Override
  public double getFixedBonus() {
    return 0;
  }

  @Override
  public double getPercentageBonus() {
    return 0;
  }

  @Override
  public List<Staff> getMinions() {
    return Collections.EMPTY_LIST;
  }

}

public static class Administrator extends Worker implements Staff {
  double fixedBonus = 2.13;

  @Override
  public double getFixedBonus() {
    return fixedBonus;
  }

}

public static class Salesperson extends Worker implements Staff {
  double percentageBonus = 3.14;

  @Override
  public double getPercentageBonus() {
    return percentageBonus;
  }

}

public static class Manager extends Worker implements Staff {
  List<Staff> minions;

  @Override
  public List<Staff> getMinions() {
    return minions;
  }
}

不要被使用instanceof和cast的陰暗面所吸引。 您會后悔您的決定。 oop的全部要點是，即使您不知道您正在處理哪種對象，也仍然可以使用它們。

Answer 3

（和清潔-的instanceof和鑄造是丑陋的），使您的客戶端代碼有很多更為簡單的選擇是聲明一個默認的實現為每個具體的方法Employee ，例如，用於返回零fixedBonus()的Employee ，但在覆蓋它Sales