63 interview questions for developers (2026)

Easy

14 votes1684 runs0 comment

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

IT Architect

OOP

javascript

undefined

Eric Hostaleryat Dec 3, 2021

Hard

13 votes869 runs0 comment

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

IT Architect

OOP

visibility

inheritance

Anonymous authorat Mar 28, 2022

Easy

10 votes888 runs0 comment

Inheritance in OOP.

IT Architect

OOP

inheritance

methods

Anonymous authorat Mar 28, 2022

Easy

9 votes701 runs0 comment

You need to develop a class for which there should be only one instance throughout your application. Which design pattern should you use for this?

IT Architect

OOP

design pattern

singleton

Jean ALbin ELieat Mar 28, 2023

Medium

8 votes1563 runs0 comment

Can we extend an abstract class in Java?

IT Architect

OOP

abstract

class

Eric Hostaleryat Dec 3, 2021

Hard

7 votes1637 runs0 comment

Which design pattern allows to dynamically add responsibilities to an object?

IT Architect

OOP

design pattern

object

Eric Hostaleryat Sep 19, 2022

Easy

7 votes867 runs0 comment

Can a class implements several interfaces ?

IT Architect

OOP

interfaces

inheritance

Anonymous authorat Mar 28, 2022

Easy

5 votes1550 runs0 comment

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

IT Architect

OOP

javascript

undefined

Eric Hostaleryat Dec 3, 2021

Easy

5 votes1550 runs

1 comment

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

IT Architect

OOP

undefined

Eric Hostaleryat Dec 3, 2021

Medium

5 votes1506 runs1 comment

Can an interface inherit from another interface?

IT Architect

OOP

interfaces

Vincent Cotroat Dec 3, 2021

Medium

5 votes834 runs1 comment

When can you do a+b in OOP ?

IT Architect

OOP

operator overloading

classes

Anonymous authorat Mar 28, 2022

Easy

4 votes1612 runs0 comment

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

IT Architect

OOP

javascript

undefined

Eric Hostaleryat Dec 3, 2021

Medium

4 votes1604 runs0 comment

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

IT Architect

OOP

javascript

undefined

Eric Hostaleryat Dec 3, 2021

Easy

4 votes1575 runs0 comment

Implement the interface IEmailFormatter for the classes Person, Company, and ListOfPerson, which has a method GetEmailContent()

IT Architect

OOP

interfaces

classes

Eric Hostaleryat Mar 13, 2023

Hard

4 votes780 runs2 comments

Which modification of the following code WILL NOT make the output be "success" ?

IT Architect

OOP

inheritance

overriding

Anonymous authorat Mar 28, 2022

Medium

4 votes653 runs0 comment

Explain the difference between overriding and overloading in OOP.

IT Architect

OOP

methods

inheritance

Anonymous authorat Mar 28, 2022

Hard

3 votes1560 runs

1 comment

What are the public methods of the class `Person`?

IT Architect

OOP

methods

visibility

Eric Hostaleryat Dec 3, 2021

Hard

3 votes1546 runs1 comment

Implement the registration method on class A in a virtual way,Override the registration method on classes A1 and A2 when implementing these classes

IT Architect

OOP

classes

inheritance

Eric Hostaleryat Dec 3, 2021

Medium

3 votes712 runs

3 comments

What does the following code return ?

IT Architect

OOP

inheritance

access modifiers

Anonymous authorat Mar 28, 2022

Medium

3 votes689 runs0 comment

Overloading an operator in OOP

IT Architect

OOP

operators

classes

Anonymous authorat Mar 28, 2022

63 interview questionsfor developers (2026)

Test your developer skills before an interview with 63 corrected questions on 80+ topics. Beginner, Intermediate or Expert level.

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

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

Inheritance in OOP.

You need to develop a class for which there should be only one instance throughout your application. Which design pattern should you use for this?

Can we extend an abstract class in Java?

Which design pattern allows to dynamically add responsibilities to an object?

Can a class implements several interfaces ?

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

Can an interface inherit from another interface?

When can you do a+b in OOP ?

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

Is the following code valid? class Person { constructor(name, age) { this.name = name; this.age = age; } } const person = new Person('John', 20); console.log(person.name); console.log(person.age);

Implement the interface IEmailFormatter for the classes Person, Company, and ListOfPerson, which has a method GetEmailContent()

Which modification of the following code WILL NOT make the output be "success" ?

Explain the difference between overriding and overloading in OOP.

What are the public methods of the class `Person`?

Implement the registration method on class A in a virtual way,Override the registration method on classes A1 and A2 when implementing these classes

What does the following code return ?

Overloading an operator in OOP