**Inheritance and member variable question**

[wonkty wang]

Hi People, I got the following question from the mock exam...

   class Exam
{
 protected String difficultyLevel = "easy";
 
public void printDifficultyLevel(){
}
System.out.println(difficultyLevel);
 
}
 
class SCJPExam extends Exam{
private String difficultyLevel = "killing";
}
SCJPExam myExam = new SCJPExam();
myExam.printDifficultyLevel(); 

The answer is that "easy" will get printed. I just dont understand it why.
As after inheritance, the subclass SCJPExam has it own copy of difficultyLevel, isn't?? Can anyone please explain here?

Thanks

[Srinivasan thoyyeti]

inheritance and polymorphism.


Here you got confused with polymorphism.

behavior(only instance-methods) can be over-ridden.

FOR state(memebers either static or non-static) , THERE IS NO POLYMORPHISM concept like overloading or over-riding.


in your example:
Move following to Child class and test it;

public void printDifficultyLevel(){
}
System.out.println(difficultyLevel);

}

[wonkty wang]

Thanks.

Yeah, I know only the member method (not the member variable)could be overridden. However,the subclass does get a copy of member variable from the super class by inheritance. I guess my question would be:

when

  myExam.printDifficultyLevel();  

get runs. why it access the superclass member variable "difficultyLevel" instead of the subclass ones.

Thanks.

[Srinivasan thoyyeti]

Now in you are in real soup.

A method in parent class(***not-over-ridden-in-child), How you can expect to access the state of child ?

*** Remember if you instantiate Child --> parent also gets instantiated.

[wonkty wang]

Thanks for your help. I think I got the whole basic concept wrong. Inheritance is the logic concept which means there is not a physically a copy of whatever member variable or member methods. I guess the subclass just has the access to the superclass's methods or variables.