Polymorphism Phone Interview Question

David Smith

So my question is not WHAT IS POLYMORPHISM? I know what the defnition of Polymorphism is

But how to answer the question in a phone interview when the interviewer says,

Were and how did you achieve polymorphism? How to answer that question without stumbling?

Can someone give me a and explicit answer as how you would answer this in an interview and apply it to the STAR method approach below?

You can make up a fake company or task and apply the example you use above into the star method. Also make your response past tense, as if it already happen. I am more concern of what did yo do. How to explain what did you do, not how can you. Explaining how can you is simple to me.

S- Situation (While working for company X.........)

T-Task (For this particular task I was responsible for......)

A-Action (The actions I took.......)

R-Result (The system implemented as team ........)

15 Replies

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David Smith11y ago

Sujeet, Ok. Lets move on. We are going in circles. The example below is converted to past tense. Please tell me what If what I am writing if true. Also let me know if I can make this example below shorter. I don't want to over explain.

A-Action:  In the software designing phase after soliciting requirements from 
           stakeholders I define and create an abstract polymorphism pattern. 
           I created an abstract vehicle class for types of vehicle, to reuse the 
           common behavior that can be use from the derived types of vehicle class.. 
           By creating an abstract vehicle class I force all sub vehicle derived
          classes to implement the common abstract methods.

Sujeet Suman11y ago
David when you got all points & only you having past tense problem. Then why not you covert the scenario in past tense.

David Smith11y ago

Sujeet, I know you did. In your version I try to applied what you stated in your example. The only difference is your example is not in past tense. Check my task. I still had to do my example to make sure others and I can understand when I explain were and why I achieved polymorphism

Is there anything I did wrong in my example?

S- Situation: I'm glad you ask. A relevant example being at my last company 
              TATA MOTOR where I collaborated with mainframe developers to 
              produce a new vehicle module for our Transportation WPF Product 
              using the MVVM architectural pattern.
T-Task: My task was to design and develop software to maintain their 
        manufacturing material data for different types of Vehicle
        like Bicycle, Car, Truck etc....
A-Action:  In the software designing phase after soliciting requirements from 
           stakeholders I define and create an abstract polymorphism pattern. 
           I created an abstract vehicle class for types of vehicle, to reuse the 
           common behavior that can be use from the derived types of vehicle class.. 
           By creating an abstract vehicle class I force all sub vehicle derived
          classes to implement the common abstract methods.
R-Result: In the end I produced a successful loose-couple, extensible, and testable 
          module for our transportation module. The stakeholders were pleased with the
          product.

Sujeet Suman11y ago

David what you need I unable to recognize now. Where as I had explained all your points.

I think through below example (which I had already posted) you can easily explain all things.

public abstract class Vehicle

{

public abstract int Wheels();

}

public class Bicycle : Vehicle

{

public override int Wheels()

{

return 2;

}

public class Car : Vehicle

{

public override int Wheels()

{

return 4;

}

public class Truck : Vehicle

{

public override int Wheels()

{

return 18;

}

S- Situation: (You are working for TATA MOTOR company as a sofrware Engineer.)
T-Task: (You have to develop a software to maintain their manufacturing material data for different type of vehicle like Bicycle, Car Truck etc.)
A-Action:  (So now in software designing phase you have to define a class structure for        different type of vehicle. So here you have seen that your requirement is to define classes for different type of vehicle first. So you defined 3 different classes Bicycle, Car & Truck. So now you should think that all vehicle having some common type of uses like tyres, engine, side mirror etc. & you have to maintain their specifications. IN DESIGNING PHASE WE ARE NOT DOING CODING ONLY DESIGNING A MODEL. So now you should create abstract class to keep commonly implemented / uses method like Wheels & inherit the abstract class by all different classes. So here you will see that all derived classes must be implement those abstract methods.
R-Result: (Then you should start implementation of design i.e. coding. So as a team you can work on & in this way your software will be developed.)

David Smith11y ago
Suthish,

The question is not what is Polymorshism. The question is explicitly How and were did you achieve Polymorphism? Also in any any interview you can use the STAR method show consistency in how you tell your story.

Suthish, in the example below, how would you explain the example below in the interview, one the interiview ask you How and were did you achieve Polymorphism?
public abstract class Vehicle

{ public abstract int Wheels; }

public class Bicycle : Vehicle { public override int Wheels() { return 2; } }
public class Car : Vehicle { public override int Wheels() { return 4; } }
public class Truck : Vehicle { public override int Wheels() { return 18;
Suthish Nair11y ago
Hi David,

First of all, how did we achieve polymorphism in the example below using the STAR method statement is wrong.

The STAR method is a structured manner of responding to a behavioral-based interview question by
discussing the specific situation, task, action, and result of the situation you are describing.

The interviewer just used a method to discuss the topic (WHAT IS POLYMORPHISM).

So What is Polymorphism, How to achieve Polymorphism etc..
Sujeet Suman11y ago
David all classes means :
abstract class Vehicle
class Bicycle

class Car

class Truck
David Smith11y ago
What are ll classes?
David Smith11y ago
Correct. Mainframe is just simply you are on a team of 6 developers. We call them mainframe developers. Meaning they are the team of developers, I am collaborating with.
David Smith11y ago
Correct. Mainframe is just simply you are on a team of 6 developers. We call them mainframe developers. Meaning they are the team of developers, I am collaborating with.
Sujeet Suman11y ago
David I think you didn't view properly my previous message.
Already I had explained every thing what you are asking in your last message.

I a have no idea about mainframe but I know MVVM. So I know in MVVM we are keeping all classes, abstract classes & interfaces in MODEL. In VIEW MODEL initializing all MODEL classes & use VIEW to user interaction.

So all your class related Polymorphic things should be appear in MODEL only.

So during interview when they ask about Polymorphism then you starts with MODEL and all same class structure as per my last message.

David Smith11y ago

Sujeet, Thanks. Let's build the example explain how did we achieve polymorphism in the example below using the STAR method. Let me know if i need to add or take away from example below

Interviewer: How and Were did you achieve polymorphism?

Response:

S- Situation: I'm glad you ask. A relevant example being at my last company 
              TATA MOTOR where I collaborated with mainframe developers to 
              produce a new vehicle module for our Transportation WPF Product 
              using the MVVM architectural pattern.
T-Task: My task was to design and develop software to maintain their 
        manufacturing material data for different types of Vehicle
        like Bicycle, Car, Truck etc....
A-Action:  In the software designing phase after soliciting requirements from 
 stakeholders I define and create an abstract polymorphism pattern. 
           I created an abstract vehicle class for types of vehicle. 
           By creating an abstract vehicle class I force all sub vehicle derived
          classes to implement the common abstract methods.
R-Result: In the end I produced a successful loose-couple, extensible, and testable 
          module for our transportation module. The stakeholders were pleased with the
          product.

Sujeet Suman11y ago

David I unable to understand your STAR method problem that what you are asking. But as per my understanding I am trying to explain your example below. Please once go through.

public abstract class Vehicle

{

public abstract int Wheels();

}

public class Bicycle : Vehicle

{

public override int Wheels()

{

return 2;

}

public class Car : Vehicle

{

public override int Wheels()

{

return 4;

}

public class Truck : Vehicle

{

public override int Wheels()

{

return 18;

}

S- Situation: (You are working for TATA MOTOR company as a sofrware Engineer.)
T-Task: (You have to develop a software to maintain their manufacturing material data for different type of vehicle like Bicycle, Car Truck etc.)
A-Action:  (So now in software designing phase you have to define a class structure for        different type of vehicle. So here you have seen that your requirement is to define classes for different type of vehicle first. So you defined 3 different classes Bicycle, Car & Truck. So now you should think that all vehicle having some common type of uses like tyres, engine, side mirror etc. & you have to maintain their specifications. IN DESIGNING PHASE WE ARE NOT DOING CODING ONLY DESIGNING A MODEL. So now you should create abstract class to keep commonly implemented / uses method like Wheels & inherit the abstract class by all different classes. So here you will see that all derived classes must be implement those abstract methods.
R-Result: (Then you should start implementation of design i.e. coding. So as a team you can work on & in this way your software will be developed.)

David Smith11y ago

Sujeet. I Completely understand what polymorphism. If you were in an interview, how would you describe this module on a phone interview using the STAR method. Below is a simple polymorphism example. No need to give me a definition of polymorphism. Let's express it verbally. Write out your response for the below example.

public abstract class Vehicle 

{ public abstract int Wheels; }  

public class Bicycle : Vehicle { public override int Wheels() { return 2; } }  
public class Car : Vehicle { public override int Wheels() { return 4; } }  
public class Truck : Vehicle { public override int Wheels() { return 18; } }

S- Situation (While working for company X.........)
T-Task (For this particular task I was responsible for......)
A-Action  (The actions I took.......)
R-Result (The system implemented as team ........)

Sujeet Suman11y ago
If you are working on some projects then I think already you had seen many times these things & scenario.

Directly I am coming on point polymorphism means: Overloading, Overriding

Overloading: So suppose you are working on a maintenance project. And you are working on a class where already parameterised constructors has defined & you need to pass some para meter. So what you will do, either add required parameter with one constructor or add new one as per your requirement. So you should not add required parameter with one constructor because this may disturb your other class dependency structure. So what you will do create a new constructor with requires parameter. That new constructor is nothing but constructor overloading.

Overriding: Suppose you need to add some custom feature to a control. Like you are using one treeview with checkbox & you would like to do something after click node or checkbox then you are overriding "OnAfterCheck" method of TreeView class (System.Windows.Forms.TreeView). i.e. when you would like to extend the features of some existing class then your need to override the existing class methods.

Now I think these are enough to say during interview.