Object Oriented Programming_Lecture 2

Object Oriented Programming

Chapter 1: Introduction to OOP

Prepared by: Mahmoud Rafeek Alfarra

2016

Outlines◉What is Object-Oriented Programming ?

◉Procedural vs. Object-Oriented Programming

◉OO Programming Concepts

◉Concept of Objects and classes

◉UML Class Diagram

◉Visibility Modifiers and Accessor Methods

◉Full Example

Lecture Let’s think on concept of Class and Object

2

ومن أعرض عن ذكري )فإن له معيشة ضنكا ونحشره يوم القيامة

(أعمىسورة طه

Classes & Objects !

o Classes are constructs that define objects of the same type.

o “Class” refers to a blueprint. It defines the variables and methods the objects support.

What is Class ?

Class Name: Circle Data Fields:

radius is _______ Methods:

getArea

A class template

o “Object” is an instance of a class.o Each object has a class which defines its data and behavior.o An object has both a state and behavior. o The state defines the object, and the behavior defines what

the object does.

What is Object?

Class Name: Circle Data Fields:

radius is _______ Methods:

getArea

Circle Object 1 Data Fields:

radius is 10

Circle Object 2 Data Fields:

radius is 25

Circle Object 3 Data Fields:

radius is 125

A class template

Three objects of the Circle class

Class & Object

Class & Object

Class & Object

Class & Object

Thinking to build class …

Any Thing

Attributes

Behavior

Each one is presented as a variable in the Class

Each one is presented as a method in the Class

A new class will be considered as a new data type, so you can declare a variables (Objects) of them and then you can set and get data to its properties.

o A Java class uses variables to define data fields and methods to define behaviors.

o Additionally, a class provides a special type of methods, known as constructors, which are invoked to construct objects from the class.

Thinking to build class …

Thinking to build class … class Circle {

/** The radius of this circle */ double radius = 1.0; /** Construct a circle object */ Circle() { } /** Construct a circle object */ Circle(double newRadius) { radius = newRadius; } /** Return the area of this circle */ double getArea() { return radius * radius * 3.14159; }

}

Data field

Method

Constructors

How to build my class?

Access_modifiers class class_name {// variables = attributes Access_modifiers class_name(par1, par2, …) {

}// behavior = methods

}

Always, the class has a method called constructorwhich gives initial values to the attributes of class

Is a reserved word The identifier of class Must be as any variable

o A class can have three kinds of members: fields: data variables which determine the status of the

class or an object methods: executable code of the class built from

statements. It allows us to manipulate/change the status of an object or access the value of the data member

nested classes and nested interfaces

Class Members

How to insatiate object?

class_name object_name = new class_name (arg1, arg2, …);

The name of class, which you want to insatiate an object of it.

Reserved word

Values based on the parameters of constructor

The name of object

UML Class Diagram

Circle radius: double Circle() Circle(newRadius: double) getArea(): double

circle1: Circle radius = 1.0

Class name Data fields Constructors and methods

circle2: Circle radius = 25

circle3: Circle radius = 125

UML Class Diagram

UML notation for objects

PracticesGroup 1Compare between constructor and methods in class.

Group 2Detect 3 classes from your bedroom and 2 objects.

Group 3Diffrenciate between Class & Object

Group 4Draw the UML Class Diagram of Course class.

Group 5Draw the UML Class Diagram of Student class.

Group 6Thinking to build Circle class.

THANKS!

Any questions?You can find me at:

Fb/mahmoudRAlfarraStaff.cst.ps/mfarraYoutube.com/mralfarra1@mralfarra