44 interview questions on Object-oriented programming - Fundamentals for developers (2025)

Easy

9 votes668 runs0 comment

Inheritance in OOP.

IT Architect

OOP

inheritance

methods

Samuelat Mar 28, 2022

Hard

9 votes646 runs0 comment

Overrided method visibility must be the same or less restrictive than the inherited method.

IT Architect

OOP

visibility

inheritance

Samuelat Mar 28, 2022

Easy

5 votes657 runs0 comment

Can a class implements several interfaces ?

IT Architect

OOP

interfaces

inheritance

Samuelat Mar 28, 2022

Medium

4 votes626 runs1 comment

When can you do a+b in OOP ?

IT Architect

OOP

operator overloading

classes

Samuelat Mar 28, 2022

Medium

3 votes549 runs0 comment

Explain the difference between overriding and overloading in OOP.

IT Architect

OOP

methods

inheritance

Samuelat Mar 28, 2022

Easy

2 votes570 runs0 comment

How to instantiate objects with a type which is derivated from an abstract type in OOP

IT Architect

OOP

design pattern

abstract

Samuelat Mar 28, 2022

Medium

2 votes535 runs1 comment

What does the following code return ?

IT Architect

OOP

inheritance

access modifiers

Samuelat Mar 28, 2022

Easy

2 votes531 runs0 comment

Encapsulation rule in Object-Oriented Programming

IT Architect

OOP

encapsulation

classes

Samuelat Mar 28, 2022

Medium

2 votes522 runs0 comment

Overloading an operator in OOP

IT Architect

OOP

operators

classes

Samuelat Mar 28, 2022

Medium

2 votes350 runs0 comment

A child class B of an abstract class A must define the abstract methods of A.

IT Architect

OOP

abstract

class

Samuelat Mar 28, 2022

Medium

1 vote610 runs2 comments

In this code, the class B extends the class A. The class B overrides the method talk() from the class A. The object b is an instance of the class B. The object a is an instance of the class A. The object a is assigned to the object b. The object a calls the method talk(). The method talk() from the class B is called.

IT Architect

OOP

inheritance

polymorphism

Samuelat Mar 28, 2023

Hard

1 vote562 runs1 comment

What does the following code return ? public class A { public void talk() { echo "I am A" } public secretTalk() { this.talk() } } public class B extends A { private void talk() { echo "I am B" } public secretTalk() { this.talk() } } A b = new B() b.talk() b.secretTalk() Answer : "I am A" "I am B"

IT Architect

OOP

inheritance

overriding

Samuelat Mar 28, 2022

Easy

1 vote528 runs0 comment

Which Design Pattern should I use if I want an object to be notified when another kind of object state changed?

IT Architect

OOP

design pattern

observer

Samuelat Mar 28, 2022

Easy

1 vote523 runs0 comment

How to apply the principle of encapsulation in OOP?

IT Architect

OOP

encapsulation

visibility

Samuelat Mar 28, 2022

Medium

1 vote171 runs0 comment

How to keep common data for the whole class in OOP?

IT Architect

OOP

class

static

Samuelat Mar 28, 2022

Medium

1 vote170 runs0 comment

Which Design Pattern should I use to give dynamically new responsabilities to an object ?

IT Architect

OOP

design pattern

decorator

Samuelat Mar 28, 2022

Medium

1 vote168 runs0 comment

How to add two vectors in a class Vector2D in OOP

IT Architect

OOP

operator overloading

classes

Samuelat Mar 28, 2022

Medium

1 vote165 runs0 comment

What are the symbols of visibility for public, protected and private in UML?

IT Architect

OOP

uml

visibility

Samuelat Mar 28, 2022

Easy

1 vote155 runs0 comment

In UML, a class is represented by a rectangle with 3 parts. From the top to the bottom, these parts are : Name, Attributes, Methods.

IT Architect

OOP

uml

class

Samuelat Mar 28, 2022

Medium

1 vote139 runs0 comment

Is it possible to create an abstract class without abstract methods?

IT Architect

OOP

abstract

class

Samuelat Mar 28, 2022

44 interview questions on Object-oriented programming - Fundamentalsfor developers (2025)

Test your technical skills before an interview of Object-oriented programming - Fundamentals with 44 corrected questions. Beginner, Intermediate or Expert level.

Inheritance in OOP.

Overrided method visibility must be the same or less restrictive than the inherited method.

Can a class implements several interfaces ?

When can you do a+b in OOP ?

Explain the difference between overriding and overloading in OOP.

How to instantiate objects with a type which is derivated from an abstract type in OOP

What does the following code return ?

Encapsulation rule in Object-Oriented Programming

Overloading an operator in OOP

A child class B of an abstract class A must define the abstract methods of A.

What does the following code return ? public class A { public void talk() { echo "I am A" } public secretTalk() { this.talk() } } public class B extends A { private void talk() { echo "I am B" } public secretTalk() { this.talk() } } A b = new B() b.talk() b.secretTalk() Answer : "I am A" "I am B"

Which Design Pattern should I use if I want an object to be notified when another kind of object state changed?

How to apply the principle of encapsulation in OOP?

How to keep common data for the whole class in OOP?

Which Design Pattern should I use to give dynamically new responsabilities to an object ?

How to add two vectors in a class Vector2D in OOP

What are the symbols of visibility for public, protected and private in UML?

In UML, a class is represented by a rectangle with 3 parts. From the top to the bottom, these parts are : Name, Attributes, Methods.

Is it possible to create an abstract class without abstract methods?

44 interview questions on Object-oriented programming - Fundamentalsfor developers (2025)

Test your technical skills before an interview of Object-oriented programming - Fundamentals with 44 corrected questions. Beginner, Intermediate or Expert level.

Inheritance in OOP.

Overrided method visibility must be the same or less restrictive than the inherited method.

Can a class implements several interfaces ?

When can you do a+b in OOP ?

Explain the difference between overriding and overloading in OOP.

How to instantiate objects with a type which is derivated from an abstract type in OOP

What does the following code return ?

Encapsulation rule in Object-Oriented Programming

Overloading an operator in OOP

A child class B of an abstract class A must define the abstract methods of A.

What does the following code return ? public class A { public void talk() { echo "I am A" } public secretTalk() { this.talk() } } public class B extends A { private void talk() { echo "I am B" } public secretTalk() { this.talk() } } A b = new B() b.talk() b.secretTalk() Answer : "I am A" "I am B"

Which Design Pattern should I use if I want an object to be notified when another kind of object state changed?

How to apply the principle of encapsulation in OOP?

How to keep common data for the whole class in OOP?

Which Design Pattern should I use to give dynamically new responsabilities to an object ?

How to add two vectors in a class Vector2D in OOP

What are the symbols of visibility for *public*, *protected* and *private* in UML?

In UML, a class is represented by a rectangle with 3 parts. From the top to the bottom, these parts are : Name, Attributes, Methods.

Is it possible to create an abstract class without abstract methods?

What are the symbols of visibility for public, protected and private in UML?