البرمجة الهدفية بلغة جافا - مفاهيم أساسية

OO

PMain Concepts of OOP

Object Oriented Programming

Prepared & Presented by: Mahmoud Rafeek Alfarra

2012

Chapter 1

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PP

http://mfarra.cst.ps

Contents

What is OOP?1

Procedural VS OO2

Main Concepts3

Focus on Class & Object4

Access modifiers 5

Access methods 6

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PPWhat is OOP?

To have a fine definition of OOP, Please note what you are showing in your class room now?

Nice, what is the properties and behavior of each of them ?

this is the OOP style.


ChairsTables Teacher

PCs..

ChairsTables Teacher

PCs..

# of legs

Type of material

Color

.

.

.

# of legs

Type of material

Color

.

.

.

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PPWhat is OOP?

Object-oriented programming (OOP): A type of

programming in which programmers define not only the

attributes, but also the types of operations that can be

applied to the data structure.

In this way, the application becomes a set of objects that

includes both data and functions.


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PPProcedural VS OO


In a way, procedural programming could also be

called linear programming. One thing happens and then

the next. Code is executed from the top of the file to the

bottom.

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PPProcedural VS OO


In OOP Code is often broken up and distributed across

multiple files, each one with a single purpose.

OOP is also more abstract than procedural

programming because it looks for patterns and

reusability.

The same code can be loaded and executed many

times to accomplish a task without having to retype it.

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PPMain Concepts


OOP

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PPAbstraction

Abstraction is simplifying complex reality by modeling classes appropriate to the problem, and working at the most appropriate level of inheritance for a given aspect of the problem.

i.e: The client cares about what functionality a car offers, not about how that functionality is implemented.


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PPEncapsulation


Units (classes) normally hide the details of their implementation from their clients.

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PPInheritance

Inheritance: is a form of software reuse in which a new class is created by absorbing

an existing class's members and embellishing them with new or modified

capabilities.


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PPPolymorphism

Polymorphism enables us to "program in

the general" rather than "program in the

specific.


http://technofriends.files.wordpress.com/2008/02/polymorphism.gif

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PPDiagram of program structure

A program consists of one or more classes.

Typically, each class is in a separate .java file.

Program

File File

File

File

ClassVariables

Constructors

Methods

Variables

Variables

Statements

Statements


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PPClass & Object

In your class room there is … tables,

chairs, students.

Each one of them is object from class.


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PPClass & Object


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PPClass & Object

A class is a description of a kind of object

In most cases, it is the objects that do the

actual work.

A class describes data, constructors, and

methods.


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PPThinking to build class …


Any Thing

Attributes

Behavior

Each one is presented as a variable in the Class

Each one is presented as a variable in the Class

Each one is presented as a method 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.

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PPHow to build my class?


Access_modifiers class class_name {// variables = attributes Access_modifiers class_name() {

}// behavior = methods

}

Access_modifiers class class_name {// variables = attributes Access_modifiers class_name() {

}// 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

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PPMy first class …


class Rectangle {public float length;public float width;public float area;

public Rectangle(){length = 1.0f;width = 1.0f;area = recArea();

}

public Rectangle(float l, float w){length = l;width = w;area = recArea();

}

public float recArea(){return length*width;

}}

Attributes(properties, instance variables)of rectangle class

Default Constructor of classIt just gives any values to properties

Overloaded constructor of classIt gives values to properties by user

Method to calculate the area of rectangle Any rectangle has an area behavior

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PPAccess modifiers

The access to classes, constructors, methods

and fields are regulated using access modifiers.

i.e. a class can control what information or data

can be accessible by other classes.

To take advantage of encapsulation, you should

minimize access whenever possible.


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PPAccess modifiers

Java provides a number of access modifiers to

help you set the level of access you want for

classes as well as the fields, methods and

constructors in your classes.


A member has package or default accessibility when no accessibility modifier is specified.

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PPAccess modifiers

4 Access Modifiers:

1. public: are visible to any class in the Java program,

whether these classes are in the same package or in another

package.

2. private: they cannot be accesses by anywhere outside

the enclosing class.


A standard design strategy is to make all fields private and provide public getter methods for them.

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PPAccess modifiers

4 Access Modifiers:

3. protected: Fields, methods and constructors declared

protected in a superclass can be accessed only by

subclasses in other packages.

Classes in the same package can also access protected

fields, methods and constructors as well, even if they are not a

subclass of the protected member’s class.


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PPAccess modifiers

4 Access Modifiers:

4. default: when no access modifier is present, any class,

field, method or constructor that has no declared access

modifier is accessible only by classes in the same package.


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PPAccess modifiers


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PPAccess methods

While properties should be private, so we need to

available using them through methods, which called

access methods.


getDatapublic data getData(){ return data;}

setDatapublic void setData(data){This.data.data;}

Access methods

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PPclass Rectangle {

private float length;private float width;private float area;public Rectangle(){

length = 1.0f;width = 1.0f;area = recArea(); }

public Rectangle(float l, float w){length = l;width = w;area = recArea(); }

public float recArea(){return length*width; }

public void setLenghth(float length){ this.length = length;}public float getLength(){

return length;}

}

Access methods


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PPاستغفروا ربكم

: ذكره تعالى ا قال

ه { ل ل ا ن كا ومام ه في ت ن وأ م ه ب ذ ع ي ل

ه ل ل ا ن كا وماهم و م ه ب ذ ع م

ن رو ف غ ت س ني رو ف غ ت س }ي: ] 33النفال [


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PP

QUESTIONS?QUESTIONS?http://mfarra.cst.ps

Thank You …Thank You …

البرمجة الهدفية بلغة جافا - مفاهيم أساسية

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