Why should we override a method?

Question

Recently I was asked this question "why should one override a method? "

I replied, if I have a class with 10 methods and I want to use all of its functionality except one method, then I will override that method to have my own functionality.

Then the interviewer replied in that case why cant we write a new method with a different name and use that method instead.

Yes this is also right. Now I am confused. What is the real objective in overriding a method?

Can anyone please tell me? Thank you all in advance.

to change an implementation. to make it more specific to the child class. — Stultuske, Jun 16 '14 at 06:57
Overriding an already implemented method is OFTEN the root cause of breaking Liskov substitution principle (very bad design). In general, we "override"/(implement rather is the more appropriate word) an interface/abstract method. — Mik378, Jun 16 '14 at 06:59
Well, tell your interviewer that should always code against interfaces, not implementations :) — Juan Antonio Gomez Moriano, Jun 16 '14 at 06:57
I know it’s tongue-in-cheek, but it doesn’t address the question at all. — Michael Piefel, Jun 16 '14 at 07:03
you are right, it just that it really shocks me that someone who is hiring does not understand the basics of OOP :) — Juan Antonio Gomez Moriano, Jun 16 '14 at 08:24

score 4 · Accepted Answer · answered Jun 16 '14 at 06:59

If you will give another name to the method in derived class, you cant invoke it with same interface. You can always invoke it through base class pointer.

i.e.

Base p = new Derived();
p.overrideMethod();

If Derived class is derived from Base then it will automatically call the derived version and not of Base. In case of different name, it is not possible. It is called code against interfaces and not implementations.

Mik378 · Answer 2 · 2014-06-16T07:07:05.480

1

I replied, if I have a class with 10 methods and I want to use all of its functionality except one method, then I will override that method to have my own functionality.

=> Very often a way to break the Liskov Substitution principle ... => very bad OO design

You have many examples on the web of this "break" but a you can find a good explanation here.

edited Jun 16 '14 at 07:07

answered Jun 16 '14 at 07:01

Mik378

21,881
15
82
180

score 1 · Answer 3 · answered Jun 16 '14 at 07:03

.

why cant we write a new method with a different name and use that method instead

It is because we want to use polymorphism. You could tell the interviewer this example: There is a module that calls specific methods on objects you give it; now imagine you can't change that module (e.g. no source). You can't tell it to use a different method but you can give it an object of a subclass which has overridden that method. To the module it will appear that nothing changed.

In practice it is also often the case that you could change that module but dont want to.

score 0 · Answer 4 · answered Jun 16 '14 at 07:00

0

The benefit of overriding is: ability to define a behavior that's specific to the subclass type which means a subclass can implement a parent class method based on its requirement.

answered Jun 16 '14 at 07:00

Sanjay Bhimani

1,593
1
15
29

score 0 · Answer 5 · answered Jun 16 '14 at 07:02

One uses interfaces to allow for multiple implementations and one uses overriding to simplify the implementation of an interface (e.g. when implementing a WindowListener, one typically extends and overrides a method of WindowAdapter so that one does not need to provide definitions for the cases where the default behavior is sufficient). Adding a new method rather than overriding would not work in this case, because the caller understands the interface and invokes its methods; the whole point of overriding here is to change the behavior for the calls to the interface. If you simply added a new function, then the caller would have to know about it, which defeats the entire isolation between the consumer of a piece of functionality and the provider of that functionality which is what interfaces are intended to provide.

score 0 · Answer 6 · answered Jun 16 '14 at 07:02

Overriding is a feature that is available while using Inheritance.

It is used when a class that extends from another class wants to use most of the feature of the parent class and wants to implement specific functionality in certain cases.

In such cases we can create methods with the same name and signature as in the parent class. This way the new method masks the parent method and would get invoked by default.

score 0 · Answer 7 · answered Jun 16 '14 at 07:13

0

The main objective of overriding is code reuseablity which can be advatageous in big projects,it also provide flexiblity means you can pass different sets of input from any class and get the output

answered Jun 16 '14 at 07:13

codegasmer

1,462
1
15
47

Why should we override a method?

7 Answers7

Linked