Chapter 1: Introduction to Object-Oriented

DDWC 2623
OBJECT - ORIENTED PROGRAMMING USING JAVA

CHAPTER 1: INTRODUCTION TO OBJECT-
ORIENTED

Prepared By:

Ts. Nik Maria binti Nik Mahamood
Course Coordinator

Reference:
Bennett, McRobb, Farmer, Object-Oriented Systems Analysis And Design using UML, Fourth
Edition, Mc Graw Hill.

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INTRODUCTION TO OBJECT - ORIENTED

1.1 What It Is Object-oriented Analysis And Design?
1.2 What It Is Object-oriented Programming
1.3 Object-oriented Concepts
1.4 Object-oriented Advantages

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1.1 WHAT IS OOAD?

• OOAD is a generic term for the ideas behind the process
we employ to analyze a problem and develop logical
solution from the perspective of objects
(things, concepts, or entities)

• Small problems do not require an exhaustive process, it is
sufficient to write pseudo code before we begin writing
code.

MORE INFO:
- Pseudo code can suffice for small problem
- Problem increase in size, the methods of OOAD becomes involve.

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WHAT IS OOA?

• Object-Oriented Analysis
– During OOA, there is an emphasis on finding and
describing the concepts or objects in the problem
domains.
– For example:
• In the case of the library information system. Some
of concepts include Book, Librarian, Borrower

MORE INFO:
See Figure 1.1 : Object-orientation emphasizes representation objects.

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WHAT IS OOD?

• Object-Oriented Design
– During OOD, there is an emphasis on defining software
objects and how they collaborate to fulfill the
requirements.
– For example:
• In the library system, a Book software may have a
title attribute and a getChapter method.

MORE INFO:
See Figure 1.1 : Object-orientation emphasizes representation objects.

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Domain Book Visualization of
concept Title domain concept

getChapter(no:int)

Representation in public class Book
an OOP language {
private String title;

public Chapter getChapter(int) {…}
}

Figure 1.1 : Object-orientation emphasizes representation objects.

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1.2 WHAT IS OOP?

• If you've never used an object-oriented language before,
you need to understand the underlying concepts before
you begin writing code.

• Defined in terms of objects and the relationships between
them. Therefore, you need to understand:
– What an object is?
– What a class is?
– How objects and classes are related
– How objects communicate by using messages

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1.2 WHAT IS OOP?

Class 1 { Class 2 {
Data Data
Methods Methods

} }

Class n {
Data
Methods

}

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1.2 WHAT IS OOP?

• An object-oriented program is made up of objects.
• It groups operations and data into modular units called

objects
• In an object-oriented programming language, objects and

object interactions are the basic elements of design.
• Every object has both state (data or attribute) and

behavior (operation or function) on data.
• Objects from the same class have the same data elements

and methods
• Objects send and receive messages to invoke actions.

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1.2 WHAT IS OOP?

Functional/data approach Object-oriented approach

Data Objects

Functions

Figure 1.2: Functional/data VS object-oriented

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1.2 WHAT IS OOP?

• Structure Programming Global data

Main program

Function 1 Function 2 Function 3

Function 4 Function 5

1.2 WHAT IS OOP?

Structured programming
• Structured programming using function
• Function & program is divided into modules
• Every module has its own data and function which can be

called by other modules.
• Example of Structured programming language

C
 Pascal

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OO programming 1.2 WHAT IS OOP?

Object 1 Object 2
Data
Data Function
Function

Object 3
Data
Function

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1.2 WHAT IS OOP?

OO programming
• Objects have both data and methods
• Objects of the same class have the same data elements

and methods
• Objects send and receive messages to invoke actions
• Example of Object-oriented programming languages:

 Java
 C++
 Object-Pascal
 Smalltalk

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1.2 WHAT IS OOP?

OO programming
• Objects have both data and methods
• Objects of the same class have the same data elements

and methods
• Objects send and receive messages to invoke actions
• Example of Object-oriented programming languages:

 Java
 C++
 Object-Pascal
 Smalltalk

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1.2 WHAT IS OOP?

Key idea in object-oriented:
The real world can be accurately described as a

collection of objects that interact.

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1.2 WHAT IS OOP?

Basic Terminology in Object-Oriented

Object
• An object - bundle of related variables and methods.
• Often used to model real-world objects that we find in

everyday life.
• Every object is an instance of (belongs to) a class.
• objects interact and communicate with each other using

messages.
• Example: person, place, thing (a noun)

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1.2 WHAT IS OOP?

Basic Terminology in Object-Oriented

Method
• A method - action performed by an object.
• Also known as function/operation
• Example:

move()
StudRegister()
calculateCPA()

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1.2 WHAT IS OOP?

Basic Terminology in Object-Oriented
Attribute
• An attribute – description of object in a class.
• Also known as state/data.

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1.2 WHAT IS OOP?

Basic Terminology in Object-Oriented

Class
• A class - blueprint or prototype that defines the variables

and the methods common to all objects of a certain kind.
• In simple terms a class is just a template for the object.
• Example:

Class: Student
Attributes: Name, course, year, cpa, cgpa, status
Method: addSubject(), dropSubject(), studResult()
Object: Ahmad, Siti, Aisyah, Sarah and etc.

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1.2 WHAT IS OOP?

Basic Terminology in Object-Oriented

For example:
Julie's car is an object. It has an state consisting of 'amount
of fuel', 'make of car', 'number of miles driven' and 'colour'
and it responds to the operations 'drive n miles', 'how many
miles have you driven?‘

Explanation:
Car is an example of a class. To make a 'real' car you have to
instantiate the class, and then you get an object such as
Julie's car which is a green Metro , Fred's car which is a red
Volvo.

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1.3 OO CONCEPTS

• There are four main principles of object-oriented
programming
– Abstraction
– Encapsulation
– Inheritance
– Polymorphism

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Abstraction & Encapsulation

• Abstraction
– Focuses on a simplified outside view of behavior,
rather than implementation (e.g. What versus How).
– For example: You talk on the phone without
considering how the signals are transmitted.

• Encapsulation
– Enclose data inside an object
– Cannot be accessed directly from outside
– Provides data security
– Also known as data hiding.

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Inheritance

• Inheritance
– The concept of using classes provides a useful way to
organize objects;
• it is especially useful because classes are reusable
or extensible.
– Inheritance means you can create new classes that
extend or are descendents of existing classes.
– The descendent classes can inherit all the attributes of
the origins (parent) class.
– Because of OOP allows inheritance, you can build
classes that are extension of existing class without
start fresh each time you want to create class.

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Polymorphism

• Polymorphism
– This ability of different objects to respond, each in its
own way, to identical messages is called
polymorphism.
– Concept of polymorphism is “one interface multiple
method”
– Object-oriented programs use polymorphism to carry
out the same operation in a manner customized to the
object.
– Eg. Superclass ‘Polygon’ has a method named getArea
getArea in Subclass ‘Triangle’  a=x*y/2
getArea in Subclass ‘Rectangle’  a=x*y

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1.4 OO ADVANTAGES

• Re-usability

- once an object class is created it can be used in other
applications

• Reliability

- reused objects have already been tested

• Extensibility

– Can derive a new class from the existing class.

QUESTION:
Discuss the concepts and advantages object-oriented approach.

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1.4 OO ADVANTAGES

• Implementation of complex program

– OO closely reflect to the real world
– So that more easier to understand the concept

• Save development time ( and cost)

- by reusing code
- once an object class is created it can be used in other

applications

• Easier debugging

– classes can be tested independently

QUESTION:
Discuss the concepts and advantages object-oriented approach.

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