Java MCQs – Encapsulation and abstraction

Step into the fascinating realm of Java’s Encapsulation and Abstraction with a collection of engaging Multiple Choice Questions (MCQs). These MCQs are like little quizzes that help you understand how Java keeps its secrets safe and organizes its ideas. Learn about encapsulation, which is like putting your code in a protective bubble, and abstraction, which is like simplifying things so you can focus on what’s important. Whether you’re new to coding or have been tinkering with Java, these MCQs are a fun way to uncover the magic behind how Java makes complex things simple and secure.

1.) Which OOP principle bundles data and methods into a single unit?

A) Inheritance
B) Abstraction
C) Encapsulation
D) Polymorphism

Answer: Option C

Explanation: Encapsulation involves grouping data (attributes) and methods (functions) into a single unit (class) to control access and ensure data integrity.

2.) What is the main purpose of access modifiers in Java?

A) To provide default values
B) To control visibility and access
C) To define the class structure
D)To initialize objects

Answer: Option B

Explanation: Access modifiers determine the level of visibility and accessibility of class members, such as attributes and methods.

3.) Which access modifier restricts access to the same package?

A) public
B) protected
C) private
D) default

Answer: Option D

Explanation: The default (package-private) access modifier restricts access to class members within the same package.

4.) What is abstraction in Java?

A) Hiding data details
B) Hiding method implementations
C) Showing essential features
D) Exposing all details

Answer: Option C

Explanation: Abstraction involves presenting only the essential features of an object while hiding unnecessary details.

5.) An abstract class cannot be instantiated because it contains…

A) Abstract methods
B) Private methods
C) Static methods
D) Public methods

Answer: Option A

Explanation: An abstract class contains abstract methods that lack implementation, and therefore, it cannot be directly instantiated.

6.) In Java, which keyword is used to define an abstract class?

A) abstract
B) class
C) interface
D) extends

Answer: Option A

Explanation: The “abstract” keyword is used to define an abstract class, which cannot be instantiated and serves as a blueprint for subclasses.

7.) Which concept provides a blueprint for a class?

A) Polymorphism
B) Inheritance
C) Encapsulation
D) Abstraction

Answer: Option B

Explanation: Inheritance allows a class (subclass) to inherit attributes and methods from another class (superclass), providing a blueprint for the subclass.

8.) What is the purpose of an interface in Java?

A) To define a blueprint for a class
B) To provide multiple inheritance
C) To create objects
D) To encapsulate data

Answer: Option A

Explanation: An interface defines a contract of methods that implementing classes must provide, serving as a blueprint for those classes.

9.) Which Java concept allows you to achieve abstraction by specifying a set of methods that must be implemented by implementing classes?

A) Inheritance
B) Encapsulation
C) Polymorphism
D) Interfaces

Answer: Option D

Explanation: Interfaces define a contract of methods that implementing classes must provide, enabling abstraction and multiple inheritance.

10.) What is the significance of a “default” method in an interface?

A) It’s an abstract method.
B) It’s a static method.
C) It provides a default implementation.
D) It’s a private method.

Answer: Option C

Explanation: A “default” method in an interface provides a default implementation that implementing classes can use or override.