Are static variables inherited

问题

I have read at 1000's of locations that Static variables are not inherited. But then how this code works fine?

Parent.java

public class Parent {
        static String str = "Parent";
    }

Child.java

public class Child extends Parent {
        public static void main(String [] args)
        {
            System.out.println(Child.str);
        }
    }

This code prints "Parent".

Also read at few locations concept of data hiding.

Parent.java

public class Parent {
    static String str = "Parent";
}

Child.java

public class Child extends Parent {
    static String str = "Child";

    public static void main(String [] args)
    {
        System.out.println(Child.str);
    }
}

Now the output is "Child".

So does this mean that static variables are inherited but they follow the concept of data-hiding?

回答1:

Please have a look into the documentation of oracle: http://docs.oracle.com/javase/specs/jls/se8/html/jls-8.html#d5e12110

Static variables are inherited as long as their are not hidden by another static variable with the same identifier.

回答2:

"Inherited" is not an ideal description of what is happening; a better way to describe it would be to say that static variables are shared among the subclasses of the base class.

All derived classes obtain access to static variables of their base classes. This includes protected variables, mirroring the situation with variables that are inherited.

The concept of hiding applies as well: when a class-specific variable str appears in the Child class, it hides the str variable of the parent class.

Note that the variable str of the base class does not become inaccessible: Child can still access it by fully qualifying with the name of Parent class.

回答3:

This is not exactly inheritance, its more like sharing having access to the static attribute of the class you are extending unless you are hiding it by declaring the same identifier in you subclass, note that in case of instance attribute if you change the value of the inherited attribute it will be changed in the super instance which was instantiated for your object but if there is another hierarchy which will be supposedly blind to your hierarchy it will not be affected.

In the case of static the parent attribute will be changed and any other hierarchy will take this effect too.

来源：https://stackoverflow.com/questions/37226269/are-static-variables-inherited

标签

java

inheritance

static

data-hiding