3.1 Introduction to OOP -part1

3.O JAVA LANGUAGE

3.1 INTRODUCTION TO OBJECT-ORIENTED
PROGRAMMING

Learning Outcome

• Introduction to Object-oriented Programming

What is Object Oriented Programming?

• Object oriented programming (OOP)
is a programming technique that uses

“objects” to design the applications and

computer programs.
• In real life, things that you see such as

cars, trees, and mobile phones are
objects. Even, you as a student / lecturer
is an object.
• An object combines data and operations
on that data into a single unit

Reason of Using Java

i. Java is simple to learn – it is designed to have a similar syntax to
C/C++. Everyone can learn it. You don’t need university degree or
expensive courses – just continue reading this tutorials and you will be
set up in no time.

ii. Java is portable – write once, run anywhere. Your code will run on
Windows, Linux and Mac with no changes required.

iii. Java is reusable – you will find tons of libraries online. You don’t need
to be a guru about every programming topic, just find the right library
and use it.

Two Key Concept of Java

Class Object

Based on OOPs, class is Object is an entity
the blueprint/ template that has state and
of an object behavior.

>>>>>>>>>

>>>>>>>>>

Terms related to Object Oriented
Programming

Class

• Class is the blueprint/ template of an object.
• It provides the state (what the objects have) : and behavior (what the objects do) for an

object

DOG

• Example 1:
▪ Class : Student
 State: first name, last name, age, address, course
Behaviour: enrol

• Example 2:
▪ Class : Dog
 State: name, colour, breed
 Behaviour : barking, wagging, fetching

Examples of Class: Student

In java program: state become
variable

In java program: behaviour
become method

Object

• Object is an entity that has state and behavior.
• An object represents a real-world entity. Any tangible or touchable entity

in the real-world can be described as an object.
• Following figure shows some real-world entities:

Three characteristics of object

01 STATE
Represents the data (value) of an object.
BEHAVIOUR It also reflects the properties of an
Represent the behavior of an object.
object such as deposit, withdraw
02

Example Of Object -DOG

OBJECT STATE BEHAVIORS

Dog Breed Bark

Age Sleep
Color Eat

Example Of Object- PEN

OBJECT STATE BEHAVIORS

Pen Colour - white Write

Recap

• A software object has state and State Behaviour
behavior.
Colour Drive
• ‘State’ refers to object’s Make Change gear
characteristics or attributes. Model Increase speed
Apply brakes
• ‘Behavior’ of the software object
comprises its actions.

• Following figure shows a software
object, a Car with its state and
behavior:

Example of Object and Class

Example of Object and Class

Example of Object and Class

Relation between Object and class

Relation between Object and class

Difference between class and object

Class Object
Class is a conceptual model Object is a real thing
Class describes an entity Object is the actual entity
Class consists of fields (data Object is an instance of a class
members) and functions

Four Characteristics of Java Language

Abstraction 1 Abstraction
Encapsulation 2 Abstraction is a process of hiding the implementation details
3 from the user. Only the functionality will be provided to the user.
Inheritance
Polymorphism 4 Encapsulation
Encapsulation is all about wrapping variables and methods in
one single unit with the sole purpose of data hiding from
external classes.
Inheritance
Inheritance is the OOP ability that allows Java classes to be
derived from other classes.
Polymorphism
Polymorphism in Java allows subclasses of a class to define their
own unique behaviors and yet share some of the same
functionality of the parent class.

Abstraction

• Abstraction is simplifying complex reality by modeling classes
appropriate to the problem.

• Abstraction means hiding the complexity and showing the easier form of
the system or

• Abstraction is mechanism to show only relevant data to the user.
▪ i.e: The client cares about what functionality a car offers, not about
how that functionality is implemented.

• Data abstraction can be used to provide security for the data from the
unauthorized methods.

Real Life Example of Abstraction in Java

• Abstraction shows only important things to the user and hides the
internal details,

• For example, when we ride a bike, we only know about how to ride bikes
but can not know about how it work? And also we do not know the
internal functionality of a bike.

Real Life Example of Abstraction in Java

• Another real life example of
abstraction is ATM Machine;

• All are performing operations
on the ATM machine like cash
withdrawal, money transfer,
retrieve mini-statement…etc.
but we can't know internal
details about ATM.

Real Life Example of Abstraction in Java

Encapsulation

• Encapsulation is all about wrapping variables and methods in one single
unit. Encapsulation is also known as data hiding.

Encapsulation

Encapsulation

• Encapsulation allows the programmer to group data and the methods
that operate on them together in one place, and to hide details from
the user.

Change Address AccountValue

Name Address

Benefits Of Encapsulation

o Encapsulation protects the integrity of
an object's data.

o Protects an object from unwanted
access by clients.
✓ A bank app forbids a client to
change an Account's balance.

o Allows you to change the class
implementation.

o Allows you to constrain objects' state

Abstraction vs Encapsulation

Encapsulation:
For the mathematical equation, shown in the figure
assume that complex functions are required→ But In
the end we obtain result for it.
Calculator shows the result of equation but hides the
implementation (calculating the result) involved
Abstraction:
The calculator shown in the figure has to be powered
by a battery source. How the battery module works
for the calculator is not necessary to know for the
user who uses the calculator.

Using battery module along with other modules we use calculator -> Thus
using Abstraction encapsulation is performed

Difference Between Abstraction And
Encapsulation

The basic difference between
“abstraction” and “encapsulation”
is that abstraction focuses on
“identifying the necessary
components for building a system”
whereas, encapsulation focuses on
“hiding the internal complexities of
a system”.

Inheritance

• Inheritance is a special type of relationship where a class acquires the inherent
properties of its parent class along with this it also contains its own exclusive
properties.

• Inheritance is the OOP ability that allows Java classes to be derived from other
classes.

• The parent class is called a superclass and the derivatives are called
subclasses.

• Subclasses inherit fields and methods from their superclasses.

Inheritance

Class: Phone (Parent Class)
• Make call
• Receive call
• redial

Telephone: (Child Class) Mobilephone: (Child Class) Smartphone: (Child Class)
• Make call • Make call • Make call
• Receive call • Receive call • Receive call
• redial • Redial • Redial
• Send messages • Send message
• Receive messages • Receive message
• Browse Internet
• Install and use applications

Polymorphism

• Polymorphism is a Greek word that means "many-shaped".

• fGoernmesr.ally, polymorphism refers to the ability to appear in many

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• Polymorphism enables us to "program in the general" rather than
"program in the specific”.

Real Life Example Of Polymorphism

Suppose if you are in (i). class room that time you behave like a student, (ii).
when you are in market at that time you behave like a customer, (iii). when
you at your home at that time you behave like a son or daughter, Here one
person present in different-different behaviors.

Real Life Example Of Polymorphism

To speak something; for example, a
cat speaks meow, dog barks woof,
etc.

Get the idea????

Summary

• Key concept in Java : class and object
• 4 characteristics of Java language

▪ Abstraction
▪ Encapsulation
▪ Inheritance
▪ polymorphism