多态-调用基类函数

Question

Is it possible to call base class function without modifying both base and derived classes?

class Employee {
    public String getName() {
        return "Employee";
    }

    public int getSalary() {
        return 5000;
    }
}

class Manager extends Employee {
    public int getBonus() {
        return 1000;
    }

    public int getSalary() {
        return 6000;
    }
}

class Test {
    public static void main(String[] args) {
        Employee em = new Manager();
        System.out.println(em.getName());
        // System.out.println(em.getBonus());
        System.out.println(((Manager) em).getBonus());
        System.out.println(em.getSalary());
    }
}

Output: Employee 1000 6000

How shall I call the Employee's getSalary() method on em object?

Answer 1

You can't. You could add a method like this to Manager if you wanted:

public int getEmployeeSalary()
{
    return super.getSalary();
}

Answer 2

改用Employee对象：

Employee em = new Employee();

Answer 3

You can call the superclass's method from within the subclass.

class Manager extends Employee {
    public int getBonus() {
    return 1000;
    }

    public int getSalary() {
    return super.getSalary();
    }
}