如何从父的静态方法调用child的静态方法？

Question

I have a Base class

public class BaseStatic {
    public static String fname = "Base";
    public static String lname = "Static";

    public static void send(){
        System.out.println("BaseStatic send");
        sendTo();
    }

    public static void sendTo(){
        //How to call from here Child's static method.
        System.out.println("BaseStatic sendTo");
    }
}

and I have a Child Class which extends it.

public class FirstStatic extends BaseStatic {
    public static String fname = "First";
    public static String lname = "Static";

    public static void sendTo(){
        System.out.println("FirstStatic sendTo");
    }
}

Now there is an Main class

public class Main {
    public static void main(String args[]){
        FirstStatic.send();
    }
}

Does java provide me a way so that when i call from Main method FirstStatic.send , It goes to send method of BaseStatic , from there i can call sendTo method of FirstStatic rather than calling sendTo method of BaseStatic

Answer 1

There is no polymorphism for static methods. Therefore, in order to call a static method x of class A , you must write Ax() .

FirstStatic.send() will call BaseStatic 's send only because FirstStatic has no static send method. However, BaseStatic 's send will always call BaseStatic 's sendTo , unless you explicitly call FirstStatic.sendTo() .

Answer 2

The commented-out sendTo() method here would have the effect of hiding the implementation of sendTo() in the base class.

public class BaseStatic {
    public static String fname = "Base";
    public static String lname = "Static";

    public static void send(){
        System.out.println("BaseStatic send");
        sendTo();
    }

    public static void sendTo(){
        //How to call from here Child's static method.
        System.out.println("BaseStatic sendTo");
    }

    public static void main(String[] args) {
        FirstStatic.sendTo();
    }
}

class FirstStatic extends BaseStatic {
    public static String fname = "First";
    public static String lname = "Static";

    //public static void sendTo(){
    //    System.out.println("FirstStatic sendTo");
    //}
}

You can do the following, of course, but the net effect is identical to the code shown above. If you need polymorphism, you'll need to do away with the statics--probably a good idea, anyway!

public class BaseStatic {
    public static String fname = "Base";
    public static String lname = "Static";

    public static void send(){
        System.out.println("BaseStatic send");
        sendTo();
    }

    public static void sendTo(){
        //How to call from here Child's static method.
        System.out.println("BaseStatic sendTo");
    }

    public static void main(String[] args) {
        FirstStatic.sendTo();
    }
}

class FirstStatic extends BaseStatic {
    public static String fname = "First";
    public static String lname = "Static";

    public static void sendTo(){
        BaseStatic.sendTo();
    }
}

EDIT: These examples are structured such that you can easily do the following to verify the behavior.

javac BaseStatic.java
java BaseStatic