受保护的变量在 Java 中的子 class 内不可访问

Question

I have the following structure -

App.java -

package JohnParcellJavaBasics.AccessModifierDemo;
import JohnParcellJavaBasics.AccessModifierDemo.*;

public class App {
    public static void main(String[] args) {
        
    }
}

AnimalApp.java -

package JohnParcellJavaBasics.AccessModifierDemo.Animal;
import JohnParcellJavaBasics.AccessModifierDemo.Animal.*;

public class AnimalApp {
    protected String animalName;
    public void myMethod() {
        
    }
}

Eagle.java -

package JohnParcellJavaBasics.AccessModifierDemo.Animal.Bird;
import JohnParcellJavaBasics.AccessModifierDemo.Animal.*;

public class Eagle extends AnimalApp {
    public void myMethod() {
        AnimalApp.animalName = "abc";
    }
}

In the file - Eagle.java , in the line AnimalApp.animalName = "abc"; below animalName there is a read line which reads -

The field AnimalApp.animalName is not visible

How can this be possible?

I am using VSCode on Ubuntu and OpenJDK 11.

Answer 1

That happens because you confusing static and instance members.

AnimalApp.animalName - is a way to refer to a static variable (by using the class name, because static variable resides on the class, they do not belong to any instance of the class and hence cant be inherited).

this.animalName or super.animalName or simply animalName - are proper ways to access instance variables