当子类在超类中受到保护时，子类如何使变量成为私有的？

Question

What is the purpose of subclass to 'privatize' a variable which is protected in superclass? For example:-

abstract public class Creature{
    protected String name;

    abstract public String getName();
    abstract public void setName(String newName);
}


public class Girafee extends Creature {

    private String name;

    public Girafee() {

    }

    @Override
    public String getName() {

        return this.name;
    }

    @Override
    public void setName(String newName) {

        this.name = newName;
    }
}

Answer 1

You didn't privatize the variable; you created the subclass's own variable with the same name. Now your class has two variables with the same simple name and both are accessible:

this.name

vs.

((Creature)this).name

Answer 2

They both are completely different instance members.

As per the definition in code , You can access super class variable in child classes and preventing child classes variable to access from out side of its class.

It's just to confuse people.Though you can, you should avoid having parent/child variables with same name.

Answer 3

Your program could also be read as: name attribute of a creature is not the same as name attribute of giraffe . It's just that they have the same spelling !

Well, your examples also points to certain nitty-gitty of data hiding.
Any use of the derived class member name will always refer to the member defined as part of the derived class. To refer to the base class member, you must qualify it with the keyword super.

public class Base {

protected String s = "Hello Base";

public void get() {
    System.out.println("Base string:" + s);
}

public static void main(String[] args) {
    Base b = new Base();
    b.get();

    Derived d = new Derived();
    d.get();

    ((Base) d).get();

    Base der = new Derived();
    der.get();

}

}

class Derived extends Base {

protected String s = "Hello Derived";

@Override
public void get() {
    System.out.println("Derived String: " + s);
}

}

Output of the Program:
Base string:Hello Base
Derived String: Hello Derived
Derived String: Hello Derived
Derived String: Hello Derived