How to use a method with an object which could be extended with different class?

I've got a main class and two inherited class:

public class mother{
    
    public String Melement;

}

and

public class boy extends mother {
    
    public String Belement;

}

and

public class girl extends mother{
    
    public String Gelement;

}

So i could have and object A like boy A = new boy(); and an object B like girl B = new girl();

And i would like to use a method with these both object, but it doesn't work

This is what i tried:

public void mymethod (moth开发者_开发技巧er MyObject) {

if (MyObject instance of boy) {

String A = MyObject.Melement;
String B = MyObject.Belement;

}

if (MyObject instance of girl) {

String A = MyObject.Melement;
String B = MyObject.Gelement;

}

}

I understand that it's not working because Muobject is of type "mother" so I could access only to "Melement" But I would like my method accept the both type of object "boy" and "girl"

Is it possible to do it? How?

---

Although it the check of instance of does work, you still need to cast it to a Boy class in order to work. Simply do String B = ( (boy) MyObject ).Belement;