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CS3391 - Object Oriented Programming

Unit – 1: INTRODUCTION TO OOP AND JAVA
Chapter
Topic Page No.
No.
1.1 Overview of OOP 1
1.2 Features/Characteristics of OOP 4
1.3 Java Buzzwords 8
Overview of Java 11
1.4 1.4.1: Basic Java Terminologies 12
1.4.2: Java Source File Structure 14
1.5 Java Data Types 19
1.6 Java Variables 21
1.7 Arrays 24
1.8 Operators 32
1.9 Control Flow Statements 42
1.10 Defining Classes and Objects 57
1.11 Methods 61
Constructors 63
Types of Constructor 63
1.12 ‘this’ Keyword 68
Constructor Overloading 70
Constructor Chaining 71
1.13 Access Specifiers 73
1.14 Static Members 75
1.15 JavaDoc Comments 79
Additional Topics 86
1.16.1: Java Comments 86
1.16.2: Java Constants 87
1.16.3: Java Identifiers 87
1.16
1.16.4: Java Keywords 87
1.16.5: Type Conversions and Casting 88
1.16.6: Garbage Collection 90
1.16.7: Using Command Line Arguments 92




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CS3391 - Object Oriented Programming 1

UNIT 1 INTORDUCTION TO OOP AND JAVA

Overview of OOP – Object Oriented Programming Paradigms – Features of Object
Oriented Programming – Java Buzzwords – Overview of Java – Data Types, Variables
and Arrays – Operators – Control Statements – Programming Structures in Java –
Defining Classes in Java – Constructors – Methods – Access Specifiers – Static Members
– JavaDoc Comments.


1.1: Overview of OOP


 OBJECT ORIENTED PROGRAMMING (OOP):

Object-Oriented Programming System (OOPs) is a programming paradigm based
on the concept of ―objects that contain data and methods, instead of just functions
and procedures.

 The primary purpose of object-oriented programming is to increase the
flexibility and maintainability of programs.
 Object oriented programming brings together data and its behavior
(methods) in to a single entity (object) which makes it easier to understand
how a program works.




 Features / advantages of Object Oriented Programming :-
1. It emphasis in own data rather than procedure.
2. It is based on the principles of inheritance, polymorphism, encapsulation and
dataabstraction.
3. Programs are divided into objects.
4. Data and the functions are wrapped into a single unit called class so that
data ishidden and is safe from accidental alternation.
5. Objects communicate with each other through functions.
6. New data and functions can be easily added whenever necessary.
7. Employs bottom-up approach in program design.

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CS3391 - Object Oriented Programming 2


 PROCEDURE-ORIENTED PROGRAMMING [POP]:
Procedure-Oriented Programming is a conventional programming which consists
of writing a list of instructions for the computer to follow and organizing these
instructions into groups known as Functions (or) Procedures (or)
subroutines (or)Modules.

Example: A program may involve the following operations:
 Collecting data from user (Reading)
 Calculations on collected data (Calculation)
 Displaying the result to the user (Printing)


Main Program
Global Data




Procedure
Procedure Procedure
3(Printing)
1(Reading) 2(Calculation)
Local Data Local Data Local Data




Characteristics of Procedural oriented programming:-
1. It focuses on process rather than data.
2. It takes a problem as a sequence of things to be done such as reading,
calculating and printing. Hence, a number of functions are written to solve a
problem.
3. A program is divided into a number of functions and each function has
clearly defined purpose.
4. Most of the functions share global data.
5. Data moves openly around the system from function to function.
6. Employs top-down approach in program design.

Drawback of POP
 Procedural languages are difficult to relate with the real world objects.
 Procedural codes are very difficult to maintain, if the code grows larger.
 Procedural languages do not have automatic memory management as like in Java.
Hence, it makes the programmer to concern more about the memory
management of the program.
 The data, which is used in procedural languages, are exposed to the whole


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CS3391 - Object Oriented Programming 3

program.So, there is no security for the data.
 Examples of Procedural languages :
o BASIC
o C
o Pascal
o FORTRAN

 Difference between POP and OOP:

Procedure Oriented
Object Oriented Programming
Programming
Divided Into In POP, program is divided into In OOP, program is divided into
smallparts called functions. partscalled objects.
In POP, Importance is not given In OOP, Importance is given to the
Importance to data but to functions as well data rather than procedures or
as sequence of actions to be functions because it works as a
done. real world.
Approach POP follows Top Down OOP follows Bottom Up
approach. approach.
Access POP does not have any OOP has access specifiers
Specifiers accessspecifier. named Public, Private,
Protected, etc.
In POP, Data can move freely In OOP, objects can move and
Data Moving from function to function in the communicate with each other
system. throughmember functions.
Expansion To add new data and function OOP provides an easy way to
in POPis not so easy. add newdata and function.
In POP, Most function uses In OOP, data cannot move easily
Data Access Global data for sharing that can from function to function, it can
be accessed freely from be kept public or private so we
function to function in the can control the access of data.
system.
Data Hiding POP does not have any OOP provides Data Hiding so
proper way for hiding data so it provides more security.
is less secure.
In POP, Overloading is not In OOP, overloading is possible in
Overloading possible. the form of Function Overloading
and Operator Overloading.
Examples Examples of POP are: C,VB, Examples of OOP are: C++, JAVA,
FORTRAN, and Pascal. VB.NET, C#.NET.




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