OOP principles overview in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Encapsulation in OOP?

Encapsulation means keeping data (variables) and methods (functions) that work on the data together inside a class. It hides the internal details and only exposes what is necessary.

beginner

Define Inheritance in simple terms.

Inheritance allows a new class to get properties and behaviors from an existing class. It helps reuse code and create a hierarchy.

intermediate

What does Polymorphism mean in OOP?

Polymorphism means one action can behave differently based on the object it is acting on. For example, the same method name can do different things in different classes.

intermediate

Explain Abstraction with an example.

Abstraction means showing only the important details and hiding the complex inner workings. For example, when you drive a car, you use the steering wheel without knowing how it works inside.

beginner

List the four main OOP principles.

The four main OOP principles are:<br>1. Encapsulation<br>2. Inheritance<br>3. Polymorphism<br>4. Abstraction

Which OOP principle means hiding internal details and showing only necessary parts?

A Inheritance

B Abstraction

C Polymorphism

D Encapsulation

Abstraction hides complex details and shows only what is needed.

What does inheritance allow a class to do?

A Hide data from other classes

B Create unrelated objects

C Change method names dynamically

D Reuse code from another class

Inheritance lets a class reuse properties and methods from a parent class.

Polymorphism allows methods to:

A Create new classes from scratch

B Hide data inside a class

C Have the same name but behave differently

D Prevent code reuse

Polymorphism means one method name can work differently depending on the object.

Encapsulation is best described as:

A Combining data and methods in one unit

B Using inheritance to extend classes

C Changing method behavior at runtime

D Showing only important details

Encapsulation groups data and methods inside a class to protect and organize them.

Which principle helps in creating a class hierarchy?

A Inheritance

B Abstraction

C Polymorphism

D Encapsulation

Inheritance creates a hierarchy by letting classes inherit from others.

Explain the four main OOP principles and give a simple example for each.

Think about how classes hide data, reuse code, behave differently, and hide complexity.

Why is encapsulation important in programming? How does it help in real-life coding?

Consider how keeping things private helps avoid mistakes.