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Amity School of Engineering

B.Tech., CSE(5th Sem.)

Java Programming

Topic: Object Oriented Programming

ANIL SAROLIYA

Amity School of Engineering & Technology

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Text/ Reference Books

JAVA for Beginners, Joyce Farrell, CENGAGE Learning

Java the complete Reference by Patrick Naughton & Herbert Schild, Tata

Mc-Graw Hill Java How to program, Deitel & Deitel, Pearson

Head First Java, Kathy Siera & Bert Bates, OReilly Media

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Home Assignment What do you know about Programming?

What is the role of Compiler & Interpreter in Programming?

What is source code?

What is Class?

What is Object?

What is Object Oriented Programming?

C++ is structured or object oriented programminglanguage. Justify this statement.

Compare Structured and Object Oriented Programming.

What is Encapsulation?

What do you know about Data Abstraction?

What is Inheritance? Also describe (in 2-3 line for each) types of inheritance.

Why the Polymorphism is used in OOP's?

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OOP DefinitionObject-oriented programming is a way of

implementation in which programs are

organized as cooperative collections ofobjects,each of which represents an instance of some

class, and those classes(categories) are all

members of a hierarchy of classes united via

inheritance relationships.''

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New Programming Paradigms Requirement

The cost of software development & maintenance is increasing substantially as

compared to the cost of the hardware of a computing system, but hardware

technology is improved.

This increasing cost in software & technological improvement in hardware demands

a cost effective & more technical compatible programming paradigm.

Software maintenance is the process of modifying or extending the capabilities ofthe existing software.

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OOPs! a New Paradigm

OOP works on data, with specific methods (functionality) in a bounded

form. Such form is termed as class

To access the class, we need an instance which can create the logicalinterface in between class & user (through main function). Such instance is

termed as Object. That why this new paradigm is termed as Object

Oriented Programming Paradigm

The power of object-oriented languages is that the programmer can create

modular & reusable code which is possible by composition andmodification of the existing modules in a program

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OOP increasing the flexibility in coding without disturbing the other part of

the code

OOP increasing the software development speedby reusing & enhancing

the existing code

Its reducing the translation burden (from a real-world representation to the

computer-world representation) for the programmer

So, Why OOP?

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An object is like a

black box.

Its a material thing

that can be seen or

touched.

The internal details

of such things are

hidden.

OO Programming

Identifying objects and

assigning responsibilities

to these objects.

Objects communicate to

other objects by sending

messages.

Messages are received by

the methods of an object7

Object

What is Object Oriented Programming?

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Tangible Things as a car, printer, ...

Roles as employee, boss, ...

Incidents as flight, overflow, ...

Interactions as contract, sale, ...

Specifications as colour, shape,

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What is an object?

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An object represents an individual, identifiable item, unit,or entity, either real or abstract, with a well-defined role

in the problem domain.

Or

An "object" is anything to which a concept applies.

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What is an object? (continued.)

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Modularity - large software projects can be split up insmaller pieces.

Reusability - Programs can be assembled from pre-

written software components.

Extensibility - New software components can be

written or developed from existing ones.

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Why do we care about objects?

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Object = Data + Methodsor

An object has the responsibility to know and

the responsibility to do.

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= +

The two parts of an object

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Features of Object Oriented Programming

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C++or

Java

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Features of OOP Contd

Encapsulation: It is a mechanism that associates the code and the data itmanipulates into a single unit and keeps them safe from external interference and

misuse. Thats why OOP is some how secure than other type of programming.Data Abstraction: The technique ofcreating new data types that are well

suited to an application or program known as data abstraction. It provides the

ability to create user-defined data types which is also known as abstract data

types (ADTs) .

Inheritance: It allows the extension and reuse of existing code without having to rewrite the code

from scratch. Inheritance involves the creation of new classes (derived classes) from the

existing ones (base classes).

It enabling the creation of a hierarchy of classes , which gives the name of relationship:

like: Parent Class & Child Class Relationship

Base Class & Derived Class Relationship

Super Class & Sub Class Relationship

Two popular forms of inheritance are single and multiple inheritance. Single inheritance

refers to deriving a class from a single base class 13

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Features of OOP Contd

Multiple Inheritance: A class is derived from more than one base class is

known as multiple inheritance. C++ supports multiple inheritance, JAVA doesn't

Polymorphism: It allows a single name or operator to be associated withdifferent operations depending on the type of data passed to it. It is normally

achieved by function overloading, operator overloading, and dynamic binding

(virtual functions)

Persistence: The incident where the object (data) survives in the program

execution time and exists between executions of a program is known aspersistence. All database systems support persistence. In C++, this is not

supported. However, the user can build it explicitly using file streams in a

program. In Java it is possible.

Delegation: It is an alternative to class inheritance. Delegation is a way of

making object composition as powerful as inheritance. In delegation, twoobjects are involved in handling a request: a receiving object delegates

operations to its delegate. This is analogous to the child classes sending

requests to the parent classes.

Genericity: Genericity is realized through function templates and class

templates. 14

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Structured Programming

Emphasis on algorithm rather than data

Programs are divided into individual procedures that perform discrete tasks

Procedures are independent of each other as far as possible

Procedures have their own local data and processing logic

Parameter passing facility between the procedures for information communication

Controlled scope of data

Introduction of the concepts of user defined data types

Support for modular programming (used to break up a large program into manageable units),

projects can be broken up into modules and programmed independently

Scope of data items is further controlled across modules

A rich set of control structures are available to further abstract the procedures

Examples: Pascal and C

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Limitations: Co-ordination among multiple programmers is required for

handling the changes made to mutually shared data items

Maintenance of a large software system is tedious and costly

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Object Oriented Programming

Depending on the object features supported, the languages are classified into two

categories:

1. Object-Based Programming Languages

2. Object-Oriented Programming LanguagesObject-based language = Encapsulation + Object Identity(means Object Name)

&

Object-oriented language = Object based language features + Inheritance

+Polymorphism

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Features of OOPSImprovement over the structured programming paradigm

Emphasis on data rather than algori thm

Data abstraction is introduced in addition to procedural abstraction

Data and associated operations are un if ied in to a single unit which is termed as Object

Programs are designed around the data being operated, rather than operationsthemselves (data decomposition-rather than algorithmic decomposition)

Relationships can be created between similar, yet distinct data types

Examples: Java, C++, Smalltalk, Eiffel. etc.

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Structured Versus Object-Oriented Programming

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In structured programming orconventional

programming or function oriented

programming orprocedural programming,

data are defined as global data and access

(or changes) by all the functions of a

program without any restriction . Due to

this data security and integrity has

reduced

whereas,

OOPs, data is encapsulated with the

associated functions (or operations),

such encapsulated formorcapsuleiscalled an object

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Structured Versus Object-Oriented Programming (contd..)

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In the OO approach. the problem is divided into objects

whereas

In FOP the problem is divided into functions

Both approaches adopt the same philosophy of divide and conquer,

but , OOP conquers a bigger region,While, FOP is conquering a smaller region

Hence, OOP contains FOPand so OOP can be referred to as the super set of FOP

(like C++. which is a superset of C)

Unlike traditional languages, OO languages allow localization of data and code and restrict other

objects from referring to its local region [see the object figure (in previous slide)]For this, OOP is centered around the concepts of objects, such as:

Encapsulations,

Abstract data types,

Inheritance,

Polymorphism,

Message based communication, etc.

During the execution of a program, the objects interact with each other by sending messages and

receiving responses.

For Example, in a program to perform withdrawals from an account, a customer object can send a

withdrawal message to a bank account object.

Means, An object communicating with other objects need not be aware of the internal work ing of

the objects with which i t interacts.

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Thanks

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Amity School of Engineering & Technology

B.Tech., CSE(5th Sem.)