Thread: My Base Class is Changing every time in my code. How I can overcome this?

I have had the below question asked in interview, i'm curious to learn the answer.

I have a base class, 'GeneratorBaseClass' that is extended by Generator. The question I was asked was about creating a new base class 'GeneratorBaseClass2' and having Generator change to extend that at run time (without having to change Generator). So, as an example of the code

public class GeneratorBase1 {
    public GeneratorBase1(){
        System.out.println("Generator Base 1 is used");
    }
}
 
public class Generator  extends  GeneratorBase1{
 
    public Generator() {
        //will call the appropriate super class
    }
    public static void main(String[] args){
        Generator test=new Generator();
    }
 
}

And I want to have Generator pick up a new GeneratorBase at run time, so change to

public class GeneratorBase2 {
    public GeneratorBase2(){
        System.out.println("Generator Base 2 is used");
    }
}

The form of Generator can be changed, but must not be changed every time the base class changes. This is about allowing the selection of base class at runtime and I don't want to just change the "extends ...." portion

Hi Kevin,
My problem is my 'generator' working fine/ remains same all the time,.Only my Base class is Changing, every time i need to update my code as,

Class generator extends generatorbase1{}
Class generetor extends generatorbase2{} and So on,.

What should i write after 'extends..' keyword that my child class[generator class] will extends automatically from the Base class which i want.
if i compile 'generator' & 'generatorbase1' it should extend from generatorbase1
if i compile 'generator' & 'generatorbase2' it should extend from generatorbase2..and So on

How can i tell in my code, that it should decide at compile time to extend.???

I can't quite tell what you want, but I think you have it backwards. If Generator extends GeneratorBase1, then it cannot also extend GeneratorBase2. Either you would want GeneratorBase1 and GeneratorBase2 to extend Generator, or have them implement Generator. You can't extend more then 1 class at all, let alone change it at runtime.

Originally Posted by theoriginalanomaly

I can't quite tell what you want

I do not understand what you are trying to ask either. Can you try to explain it another way?

My understanding is that if you write and compile "class Foo extends Bar {" that's it: game over. Foo will extend Bar, and Bar will be the immediate parent class of Foo for all time.

@OP: If you have the exact wording of the question that might help. For instance it is possible that some specific functionality was desired and some other mechanism (not "extends") is possible.

Originally Posted by theoriginalanomaly

I can't quite tell what you want, but I think you have it backwards. If Generator extends GeneratorBase1, then it cannot also extend GeneratorBase2. Either you would want GeneratorBase1 and GeneratorBase2 to extend Generator, or have them implement Generator. You can't extend more then 1 class at all, let alone change it at runtime.

i know it cannot extend more then 1 class, I'm not doing this at time.
I have had the below question asked in interview,Lets clear it.
I have a generator class which is extending Generatorbase1[Which has some values x=10,y=8], in version1 of my code.
After some days my version change to version2, in that my [values x=5,y=3] values will change with the different class name Generatorbase2{}.
in version 1 : Class generator extends Generatorbase1{...}
In version 2, my entire generator class code will remains same only in need to update the existing code as
Class generator extends Generatorbase2{...},.and So on my version's changing frequently. Every time need time update code for this small change,.How can i Overcome this??

Can you suggest me any way to resolve this ???

Originally Posted by helloworld922

A few important questions to ask (quite similar to each other, just slightly different):

1. What is the lifetime of GeneratorBase{n}? If you've gone to using GeneratorBase3, are you going to keep and use GeneratorBase2 at the same time in your program? What about GeneratorBase1?

2. Are there any other classes which need to have similar changes made, or is there only the one Generator class which extends Generator?

3. Why do you have GeneratorBase{n} to begin with? Can the Generator class be used directly with no GeneratorBase{n} class?

4. What is the background for why this structure was adopted in the code, specifically how does other code use these classes?

5. Why is manually changing which class the Generator class extends inconvenient/undesirable?

Depending on the answer to each of these questions, a preferable solution changes.

1. i'm not using the all base classes at the same time,.as my version changes my need also changes,..GeneratorBase1,GeneratorBase2 is no longer to Use.
if my requirement is comes[i.e GeneratorBase1{} ],. then ill compile my generator class and GeneratorBase1, in this condition my generator class automatically extends GeneratorBase1{}, if my requirements tells me that i should use GeneratorBase2{}.then ill compile my generator class and GeneratorBase2,this condition my generator class automatically extends GeneratorBase2{}.

2.Only one generator class extends generator. In my entire project only two files,.my generator class & my base class.[GeneratorBase1{},GeneratorBase2{}...& So on].When new version of base class comes into picture,.ill remove my old base class from project & keep new base class file[GeneratorBase3{}...]. This time i just compile the code,..it automatically extend GeneratorBase3{}.

3. No i can't use generator class w/o GeneratorBase class{}

4. My generator class is have tons of lines of code.which do some unique work. i don want that it should be change. but as my base classes are changing, i have to change my code. So i don wan't do that,.
What should do,.such that ill just compile my generator class & GeneratorBase{n}, it automatically extend it

5. If my new base class comes into picture, i'm changing code
Example : if my Previous Code like this
Class generator extends GeneratorBase1{}

if my requirement changes to extend new GeneratorBase2{}, i need to modify as
Class generator extends GeneratorBase2{}....

Please suggest me the right way

Hi helloworld92,
I had been asked this question in Job Interview, I don know what is their Project Design.
They Just asked this is the design & how you resolve this.
And I'm really interested know the answer.
I don know what will be the answer, i Just want to know Is this scenario is possible in java?? if yes, they How ?