1Intro.PPT

eACCP/Object Oriented Concepts and Java 2/Session 1/ 1 of 26
Object Oriented Programming
Approach
Session I

eACCP/ Object Oriented Concepts and Java 2/ Session 1/ 2 of 26
Session Objectives
 Explain structured programming and its
drawbacks
 Discuss Object Oriented Programming and its
advantages
 Define classes and objects
 Identify properties and methods
 Explain public and private sections of a class
 Discuss abstraction and encapsulation
 Describe inheritance and polymorphism

Structured Programming - I
mainprg()
{
Print “Hello World”
result = 13*12/2.5
Print “Result =” result
}
Program is a set of tasks
Broken down into
smaller and independent
functions
Structured programming follows a ‘top-down’ approach
sometimes termed as ‘step-wise refinement’.

Structured Programming - II
 A program is organised into a hierarchy of
modules
 Each module or function has a single entry
and exit point
 Three types of control flow:
 Sequential
 Test
 Iteration

Disadvantages of Structured
Programming
 Difficult to separate data from functions
that manipulate it
 Solutions are recreated and not reused
 Difficult to track and manage changes
Object oriented programming provides techniques for
managing complexity and reuse of software

The Object Oriented Approach -I
 Object oriented programming grew in the
70’s as a solution to the problems of
structured programming
 Models human thought process as closely as
possible
 Deals with data and procedures that operate
on data as a single ‘object’

The Object Oriented Approach - II
All around us in the real world are
objects.
Each object has certain
characteristics and exhibits
certain behaviour

The OO Approach - An Example
Top-Down approach OOP
We are going to build a hotel We are going to build a 10
storey hotel with ordinary,
deluxe and luxury suites
that also possesses an
executive lecture hall
We are going to then design
several floors, rooms and
then the lecture hall
We are going to build a
hotel along these
specifications(components)

The OO Methodology
The four steps in this methodology are:
 Identify the problem
 Identify the objects needed for the solution
 Identify the messages to be sent to the
object
 Create a sequence of messages to the
objects that solve the problem

Object Oriented Programming
OOP (Object oriented Programming) offers a powerful
model for writing software. Here:
Accounts
Data:
•No. of employees
•Salary statements
•Bills
•Vouchers
•Receipts
•Petty cash records
•Banking data
Functions:
•Calculate salary
•Pay salary
•Pay bills
•Tally accounts
•Transact with
banks
Code & Data
Object

Basic Object Oriented Concepts
 Object
 Helps to understand the real world
 Provides a practical basis for computer applications
 Class
 Describes a set of related objects
 Property
 A characteristic of an object – also called attribute
 Method
 An action performed by an object

Abstraction - I
 A process of examining certain aspects of a
problem as relevant to a particular
application
Method 1

Abstraction - II
Abstraction is classified into two
 Data abstraction
 Identifying the properties related to a particular
application
 Procedural abstraction
 Applying focus on the arguments and the return
value of the procedure rather than its
implementation

Inheritance
Inheritance is a
property that
allows reuse of
an existing
class to build
a new class
Animals
Reusability can be
achieved through
inheritance
Insects Mammals Reptiles Amphibians
Humans Non-Humans

Reusability
Programs can be broken
into reusable objects
Existing classes can be
used with additional
features
Shape

Encapsulation
 A process of information hiding
 Selective hiding of data
 Prevents accidental tampering of data
 Errors are easier to isolate and fix

Polymorphism
 Same functions with different behaviour on
different classes
Class -
Artiste
Dancer Poet
Sculptor
Here, a method
method perform()
implemented on the
subclasses would
give different results

More on Classes
 A class contains
 Data members
 Functions
 Data members are accessed through the
functions
 An object is an instance of a class
 A class can have sections which are not
accessible to other classes

A Class Definition
class Animal
{
public int noOfLegs;
public String name;
private char gender;
public void showData()
{
display(“Name :” + name);
display(“Number of Legs:” + noOfLegs );
display(“Gender :” + gender);
}
}

Access Specifiers of a Class
Class
Data or
functions
Data or
functions
Private
Public
Not
accessible
from outside
the class
Accessible
from outside
the class

Member Function
 Is a message to an object
 Is usually declared public
 Should not have the same name as a data
member
 Provides access to the data members of a
class

Using the Class
 Instantiating a class
 Animal anim1=new Animal();
 Assigning values
 anim1.name = “zebra”;
 Calling member functions
 anim1.showData();

Passing and Returning Objects
Compiler
creates a
FORMAL
variable in
the called
function
All data members of the object are copied to the
formal variable and they can be assigned any value
Formal
variables
Function

Object Oriented Languages
 Some of the leading object oriented
languages are:
 C++
 Smalltalk
 Eiffel
 CLOS
 Java

What is Java ?
Java is a high level programming
language introduced by Sun
Microsystems in June 1995
It provides for interactive processing and for the use of
graphics and animation on the Internet.
James Gosling
It was developed by a team under
James Gosling

Features of Java
 Simple
 Object oriented
 Platform independent
 Robust
 Secure
 Distributed
 Multithreaded
 Dynamic

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