How do subclasses modify private properties by inheriting the public method of parent class?

The mechanism for subclasses to modify the private properties of the parent class through inherited public methods

In object-oriented programming, subclasses inherit the parent class's method, which seems to bypass the access restrictions of private attributes and modify the private attributes of the parent class. This actually reflects the clever combination of encapsulation and inheritance mechanisms.

Let's analyze the following code example:

Parent Employee :

 public abstract class Employee {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public abstract void showMsg();
}

Subclass Manager :

 public class Manager extends Employee {
    private Clerk clerk;

    public Manager() {}

    public Manager(Clerk clerk) {
        this.clerk = clerk;
    }

    @Override
    public void showMsg() {
        System.out.println(this.getName());
    }
}

Test class:

 public class Test {
    public static void main(String[] args) {
        Manager manager = new Manager();
        manager.setName("John Doe");
        System.out.println(manager.getName()); // Output John Doe
    }
}

The key is: subclass objects have both parent and child classes. Although manager object is of Manager type, it is also an instance of Employee type. manager.setName("John Doe"); This line of code calls the setName method inherited from Employee . The setName method, although defined inside the Employee class, has permission to modify name of the private property of Employee class.

Therefore, the subclass does not directly access the private properties of the parent class, but indirectly modify the private properties of the parent class through the public method ( setName ) provided by the parent class. This does not violate the encapsulation principle, because the parent class itself allows name attribute to be modified through setName method. This design pattern allows the parent class to control access to private attributes, while also allowing the subclass to modify these attributes through inherited methods, thereby achieving flexible code structure and data management. This is exactly the essence of the encapsulation and inheritance mechanism.

The above is the detailed content of How do subclasses modify private properties by inheriting the public method of parent class?. For more information, please follow other related articles on the PHP Chinese website!