BITS PilaniPilani CampusBITS PilaniPilani Campus

Avinash GautamDepartment of Computer Science and Information Systems

BITS Pilani

BITS PilaniPilani Campus

Object-Oriented Programming (CS/IS F213)Avinash Gautam

avinash@pilani.bits-pilani.ac.inChamber# 6121-Y, NAB

Consultation HourBy appointment through mail

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Lecture-1 [OOP Basics]

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Programming Paradigms Structured programming Object oriented programming

OOP Concepts What is an object? What is a Class? What is Inheritance? What is an Interface?

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Programming Paradigms […1]

• High Level Languages (1960)– Large complex programs difficult to manage and maintain

• Structured Programming (1970)– Logically structure the program separate smaller more

manageable components– Significant problems persisted

• Understanding the systems we need to create• Changing existing software as users requirement change

• Modular languages (1980)– Modula2 and ADA, precursor to modern OO Languages

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Programming Paradigms […2]

• Object Oriented Paradigm and Component Based Software Development (1990)– Became the norm from 2000 onwards– Lead to the development of software components

where the operation of the software and the data it operates on are modeled together

– Lead to the development of reusable software components

• Save significant development time and cost• Allow better software models to be produced which are

more maintainable and easier to understand

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OOP Concepts

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What is an object?

Look around you and identify some objectsReal world objects share two characteristics

They all have state They all have behavior

Identifying the state and behavior for real-world objects is a great way to begin thinking in terms of object-oriented programming

Two Questions What possible states can this object be in? What possible behavior can this object perform? Write down your observation

Real world objects vary in complexity (Radio, Table Lamp)Objects may contain other objectsThese real world observations all translate into object oriented

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What is an object? (Contd.)

Software objects are conceptually similar to real world objects: they too consist of state and related behavior

An object store its state in fields and exposes its behavior through methods

Methods operate on objects internal state and serve as the primary mechanism for object-to-object communication

Hiding internal state and requiring all interaction through an object’s method is known as data encapsulation - a fundamental principle of OOP

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Bicycle - By attributing state and providing methods for changing that state, the object remains in control of how the outside world is allowed to use it. For example, if the bicycle only has 6 gears, a method to change gears could reject any value that is less than 1 or greater than 6.

Benefits of building code into individual software objects

Modularity Information-hiding Code re-use Plug-ability and debugging ease

What is an object? (Contd.)

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What is a Class?

• A class is a blueprint or prototype from which objects are created

• A class defines the general nature of a collection of objects of the same type

• The process creating an object from a class is called instantiation

• Every object is an instance of a particular class.• There can be many instances of objects from the same

class possible with different values for data

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Example

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class Rose

blueRose

redRose

class

objectsObject References

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What is Inheritance?

Different kinds of objects have a certain amount in common with each other

For example mountain bikes, road bikes, and tandem Bikes all share the characteristics of bicycles (current speed, current pedal cadence, current gear)

Yet each also defines additional features that make them different: tandem bicycles have two seats and two sets of handlebars; road bikes have drop handlebars etc

Object-oriented programming allows classes to inherit commonly used state and behaviour from other classes

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What is Inheritance?

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What is a Interface?

• Objects define their interaction with the outside world through the methods that they expose

• Methods form the object's interface with the outside world

• The buttons on the front of your television set, for example, are the interface between you and the electrical wiring on the other side of its plastic casing. You press the "power" button to turn the television on and off

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Questions

• Real-world objects contain _____ and ________• A software object's state is stored in its _____• A software object's behaviour is exposed through

_______• Hiding internal data from the outside world, and

accessing it only through publicly exposed methods is known as data ___________

• A blueprint for a software object is called a ____• Common behaviour can be defined in a _________

and inherited into a _______

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state behaviour

fields

methods

encapsulation

class

super-class

sub-class

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THANK YOU1. The material presented in these slides is used only for academic

purpose

2. Copyright © Oracle Sun Microsystems