Introduction to Inheritance Interview Questions and Answers

Inheritance is a very popular and a common word for all the techies who belong from a development background. This is among the core features of object-oriented programming paradigm popularly known as OOPs. Many programming languages such as Java, C++, Lisp, Perl, Python, Scala, etc. support inheritance in some way or the other.

The core fundamental idea behind inheritance is the use of classes and objects which acquires the similar properties of other entities and thereby reducing the additional effort of reprogramming and rebuilding that piece of code. This helps in keeping the class file short, precise, crisp and of a comparatively lower cost with respect to space-time complexity. Here, in this article, we are going to present for you a list of inheritance interview questions.

Now, if you are looking for a job which is related to Inheritance then you need to prepare for the 2020 Inheritance Interview Questions. It is true that every interview is different as per the different job profiles. Here, we have prepared the important Inheritance Interview Questions and Answers which will help you get success in your interview.

In this 2020 Inheritance Interview Questions article, we shall present 10 most important and frequently asked Inheritance interview questions. These questions are divided into two parts are as follows:

Part 1 – Inheritance Interview Questions (Basic)

This first part covers basic Inheritance Interview Questions and Answers

Q1. What are the different other OOPs techniques apart from inheritance? Why is multiple inheritances not supported by Java language?

Answer:
Different Object Oriented Programming techniques are Abstraction, Encapsulation, and Polymorphism. Java supports a lot of other features but not multiple inheritances because it would create ambiguity and would bring a lot of confusion and chaos. Let’s give you more insight about it by making use of an example.
Suppose, we have created two classes A and B with the same method name: hello() and we have also created another class C which is extending/inheriting the characteristics and the properties of the classes of A, B. Now, the java compiler will not be able to understand the hello() method which is extended by the class C is the result of which class and this calls for ambiguity.

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Q2. Why can’t you inherit a constructor?

Answer:
When we say that we can’t inherit a constructor, it means that a subclass instance cannot be created by making use of any of the superclass constrictors. You cannot do this because you do not want the properties of a superclass constructor to be overridden. This would have been possible if the inheritance was in the picture but it is not because doing that would conflict with another concept known as Encapsulation.

Q3. Explain the differences between inheritance and composition.

Answer:
The difference between inheritance and composition are as below:

S.No.	Inheritance	Composition
1.	Is defined by the IS-A relationship	Is defined by the HAS-A relationship
2.	Base class carries a derived object definition and therefore is tightly bound	An external link to the composing classes is held by the composing object and therefore composition is loosely bound
3.	Runtime polymorphism	Dependency Injection
4.	Unit classes can only inherit single classes	Unit class components can be composed with more than one class at a time
5.	Relationship among classes	Relationship among objects

Q4. Explain the usage of inheritance.

Answer:
This is the basic Inheritance Interview Questions asked in an interview. Classes are extended whereas interfaces are implemented in case of inheritance, There is a slight variation in the above definition. An interface extends an interface and a class implements an interface in case of inheritance. The class/interface which is the derivative one is also known as the subclass or child class or base class and the parent class is also known as the superclass which provides its properties to the class extending it

Q5. Can multiple interfaces be implemented? Can multiple interfaces be extended by a single interface?

Answer:
Yes, that is possible. For example, properties such as Serializable and Comparability can coexist in a class and therefore this feature can also promote the use of polymorphism. Yes, a single interface is capable of extending multiple interfaces. To cite an example, the interface java.util.The list extends both the Iterable and Collection interface.

Part 2 – Inheritance Interview Questions (Advanced)

Let us now have a look at the advanced Interview Questions.

Q6. Why cannot private methods be overridden?

Answer:
The subclass did not inherit the properties of a private method and therefore it cannot be overridden. Moreover, this kind of method is invisible to all the entities operating outside the class and the call to it is taken care at the compile time itself by making use of Type.

Q7. In the context of inheritance, java.lang. The object class is one major class with which all other java classes are inherited. Comment on the inheritance for interfaces. Are Object classes responsible for their inheritance?

Answer:
No, in the case of java, only object classes are responsible for providing an inheritance to classes and interfaces are exempted. On the contrary, the classes which are responsible for implementing interfaces have their root level of inheritance from Object classes.

Q8. Can subclass inherit static members?

Answer:
No, inheritance of static members is not possible but subclass, as well as the superclass, can both consist of the static method with a common signature. The subclass will have consisted of the properties of the static member of the superclass.

Q9. Explain the different types of inheritance.

Answer:
This is the popular Inheritance Interview Questions asked in an interview. Different kinds of inheritance are:

Single Inheritance: In this kind of inheritance, the properties of a single class are extended by other single classes.
Hierarchical Inheritance: In this kind of inheritance, multiple classes extend a single class.
Multilevel Inheritance: In the case of multilevel inheritance, a class is inherited by a class which again is inherited by another class thereby forming a multilevel chaining mechanism of inheritances.
Multiple Inheritance (Not supported for classes in Java): Multiple classes are extended by a single class and therefore it can be said to have above inheritance’s combination. This can be achieved by making use of interfaces.
Hybrid Inheritance: (Not supported for classes in Java): It is essentially a combination of multilevel inheritance and multiple inheritances where a single class is derived from more than one class and the parent class is supposedly a derived class and not a base class.

Q10. Is it possible to downgrade the visibility of an overridden or an inherited method?

Answer:
No, reducing visibility is not possible.

Conclusion

In this post, we read about inheritance interview questions. These questions are targeted to give you a fair idea about the concepts of inheritance. There are other underlying features of object-oriented programming language which could be asked by the interviewer. Apart from just concepts, you should also prepare to solve any code outputs and debug inheritance related questions. I hope you liked this article. Keep following us for plenty of other good articles about various technology.