Basic Principles Of Object Oriented Programming English Language Essay

Published:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

For you new programmers or programmers new to OOP, this article will briefly explain the four principles that make object-oriented languages: encapsulation, data abstraction, polymorphism and inheritance. All the examples in VB.Net, because I think it's easier for new programmers to read and understand the PLO in the first place. Of course, I do not think I said you need a language. NET on the other, because they are all based on the CLR / CLS, and finally all together in one compilation of the language. His preference, which determines the language you use. Of course, there are other OOP languages out there, as Ruby, an object-oriented language that is pure and hybrid languages such as Python, C and Java, to name a few.

Encapsulation:

What is encapsulation? Well, in general, encapsulation to hide implementation data by restricting access to the access and switches. First, let's define the access and switches.

Accessor: Access is the method used to object to ask yourself. In OOP, they tend to be in the form of properties, which under normal circumstances, GET method, the method of access. However, access methods are not limited to properties and public method that gives information about the state of the object.

Public class person

"We use private property to perform here to hide

"Name, which is used for internal implementation of the individual.

Private _fullName As String = "Raymond Lewallen"

"It acts as an access. For the applicant, he hides

Realization of the full name and where he is and what

In determining its value. It gives only the state FullName

Person object, and nothing more. In another class, please call

"Person.FullName () returns" Raymond Lewallen ".

"There are other things we need to create an instance of

"Not first class, but that's another discussion.

FullName Property Public ReadOnly () As String

Get

Back _fullName

Get end

End Property

End Class

Mutator:

Setters are public methods that are used for object's status to change, while hiding implementation, as it is changing the data. Switches are often different parts of the building above, but this time the method of its game, which allows the caller to change according to participants in the wings

Public class person

    "We use private property to perform here to hide

    "Name, which is used for internal implementation of the individual.

    Private _fullName As String = "Raymond Lewallen"

 

    "This building is currently the getters and setters. We still have

    Covert FullName.

    Public Property FullName () As String

        Get

            FullName Back

        Get end

        Set (ByVal value as String)

            Value _fullName =

        Set end

    End Property

End Class

Well, now you can look at another example, access, and the switch includes:

Public class person

    Private _fullName As String = "Raymond Lewallen"

 

    "This is another example of the access method

    "If this time we use the function.

    Public GetFullName () As String

        Back _fullName

    End Function

 

    "This is an example of one mutator method

    "If this time we use a subroutine.

    Public Sub setFullName (ByVal NewName As String)

        _fullName = NewName

 End Sub

 End Class

Thus, the use of access and switches have many advantages. Hiding the implementation of our class Person, we can make changes to class rights without fear that we are violating the code that uses the other, and encouraging class person for the information. If we wanted, we could see the full name of the string to change to an array of unique characters (FYI, this is what the string object is actually behind the scenes), but the call never know, because we will always return a string FullName, but behind scenes that we are dealing with an array of characters instead of a string object. Transparent to the rest of the program. This type of data protection and the implementation is called encapsulation. Think about access and manipulators, some of the information surrounding the form class.

Abstract:

Data abstraction is the simplest principles of understanding. Data extraction and encapuslation closely linked, since a simple definition of data abstraction is the development of classes, objects, data types, in accordance with their interfaces and functionality, not implementation details. Abstraction refers to the model, view, or another representative nominated for the real object. His development of the software object to represent an object, we find in the real world. Encapsulation hides the implementation details.

Abstraction is used to manage complexity. Developers use abstraction to decompose complex systems into smaller components. Progress and development, programmers familiar with the functions that they can expect from unused subsystems. Thus, programmers are not charged waysin taking into account that the implementation of subsystesm later, the drafting of earlier influences.

The best definition of abstraction that I have ever read this: "abstraction provides the essential features of an object that distinguish it from all other kinds of objects and thus provide a clearly defined conceptual boundaries, relative to the eye of the beholder." - G. Booch, Object-oriented design with applications, Benjamin / Cummings, Menlo Park, Calif., 1991.

Public class person

 

    Private _height As Int16

    The depth of the Public Domain () As Int16

        Get

            Return _height

        Get end

        Set (ByVal Value Int16)

            _height = Value

        Set end

    End Property

 

    _weight As Int16 Private

    Weight of the public domain () As Int16

        Get

            Back _weight

        Get end

        Set (ByVal Value Int16)

            Value _weight =

        Set end

    End Property

 

    _age As Int16 Private

    Age of public ownership () As Int16

        Get

            Back _age

        Get end

        Set (ByVal Value Int16)

            Value _age =

        Set end

    End Property

 

    Public Sub Sit ()

        Code, that person is sitting

    End Sub

 

    Public Sub Run ()

        Code, that person's authority

    End Sub

 

    Public Sub Cry ()

        Code that someone cries

    End Sub

 

    Public CanRead () As Boolean

        The code that determines whether a person who can read

        And give true or false

    End Function

 

End Class

Inheritance:

Now let's talk about heritage. Objects can relate to each other or with the "A", "use" or "relationship. "Is" is the way of heritage object relations. An example of what has always stuck with me over the years is the library (I think I could read something written by Grady Booch). So take the library, for example. More than one library makes books, but also magazines, audio and microfilm. At some level, all these elements are treated equally: four types of assets represent a library that can be equivalent to men. However, even if the four species can be considered as well, they are not identical. The book ISBN and charger is not. And audio tapes duration of the game and microfilm can be checked during the night.

Each of these library resources should be provided its own definition of the class. Without inheritance, each class independently perform functions common to all credit assets. All assets, either check or available for order. All assets have a name, date of purchase and replacement cost. Instead of duplicating functions inherited inheriting functionality from another class, called the base class or superclass.

Let's look at the major asset classes of credit. It will be used as a basis for asset classes such as books and audio cassettes.

Public Asset Class Library

 

    _title As String Private

    State property () As String

        Get

            Back _title

        Get end

        Set (ByVal value as String)

            Value _title =

        Set end

    End Property

 

    _checkedOut As Boolean Private

    CheckedOut Public Domain () As Boolean

        Get

            Back _checkedOut

        Get end

        Set (ByVal value as Boolean)

            Value _checkedOut =

        Set end

    End Property

 

    How _dateOfAcquisition private DateTime

    DateOfAcquisition Public Domain () As DateTime

        Get

            Back _dateOfAcquisition

        Get end

        Set (ByVal value as DateTime)

            Value _dateOfAcquisition =

        Set end

    End Property

 

    _replacementCost As Double Private

    replacement cost in the public domain () as double

        Get

            Back _replacementCost

        Get end

        Set (ByVal value as Double)

            Value _replacementCost =

        Set end

    End Property

 

The end of the library asset classes is a superclass or base class that contains data and methods common to all assets of the post supports. Books, magazines, audio and microfilm all subclasses or derived classes or library of asset classes and they inherit these characteristics. Inheritance relationship is called a "relationship. Book of the Library's assets, as well as three other assets.

Let the classes of books and audio cassettes, which are inherited from the asset class library:

Public class Book

    Inherited assets library

 

    _author As String Private

    The author is in the public domain () As String

        Get

            Back _author

        Get end

        Set (ByVal value as String)

            Value _author =

        Set end

    End Property

 

    _isbn As String Private

    Isbn Public Domain () As String

        Get

            Back _isbn

        Get end

        Set (ByVal value as String)

            Value _isbn =

        Set end

    End Property

 

End Class

 

Public class Audio Cassettes

    Inherited assets library

 

    _playLength As Int16 Private

    Play the length of the Public Domain () As Int16

        Get

            Back _playLength

        Get end

        Set (ByVal Value Int16)

            Value _playLength =

        Set end

    End Property

 

End Class

Now, let's take an instance of the book, so we have a new book in the library list for registration:

Sun MyBook Book = New Book

 myBook.Author = "Sahil Malik"

 myBook.CheckedOut = False

 myBook.DateOfAcquisition = # 15/02/2005 #

 myBook.Isbn = "0-316-63945-8"

 myBook.ReplacementCost = 59,99

 myBook.Title = 'Best book you ever buy Ado.Net "

You see, when we have a new book, we have all the features an asset class library at our disposal, but also because we have inherited from the class. Methods can be inherited. Let's add some methods to our asset class library:

Public Asset Class Library

 

    "Imagine that the above properties

 

    Public Sub exit ()

        If not, then _checkedOut _checkedOut = True

    End Sub

 

    Public Sub Estimate ()

        Then, if _checkedOut _checkedOut = False

    End Sub

 

End Class

Polymorphism

Polymorphism means one name many forms. Polymorphism manifests itself in multiple methods with the same name but with slightly different functionality. VB6ers Many customers are familiar with the interface polymorphism. I'm not going to discuss the polymorphism in terms of inheritance, and the part that is new to many people. For this reason it may be difficult to fully understand the potential for polymorphisms to yield in practice and what is happening in different situations to see. We will only talk about polymorphism, as well as other actors at the beginning of the study.

There are two types of polymorphism. Overridden, also known as run-time polymorphism, and overloading, which is called the compilation of polymorphism. This difference, method overloading, the compiler determines which method will be executed, and that decision is made when the code is compiled. Which method will be used to override the method determined at runtime based on dynamic type of object.

Public class MustInherit asset library

 

    Penalty for lack of a single day for overdue items

    Private _finePerDay Const As Double = 1.25

 

    "Term for an item that has been tested

    How _dueDate private DateTime

    Public Property DueDate () As DateTime

        Get

            Back _dueDate

        Get end

        Set (ByVal value as DateTime)

            Value _dueDate =

        Set end

    End Property

 

    "Calculate the amount of the fine standard for the delay element

    CalculateFineTotal Overridable Public Function () as double

        As Int32 = daysOverdue CalculateDaysOverdue (Sun)

        If daysOverdue> 0 Then

            Go _finePerDay daysOverdue

        Other

            0.0 Back

        End If

    End Function

 

    'Calculate the number of days late for a return

    CalculateDaysOverdue protective function () As Int32

        (DateTime.Now DateInterval.Day, _dueDate, ()) DateDiff Back

    End Function

 

End Class

 

"The class that inherits from the library assets Magazine

NotInheritable Public Class Magazine

    Inherited assets library

 

End Class

 

The book is a class inherits an asset library

NotInheritable Public Class Book

    Inherited assets library

 

    "It's morphing CalculateFineTotal () function of the base class.

    "This feature replaces the base class, and any appeal

    From any class copy of the book CalculateFineTotal

    "With this feature, not a base class function.

    "This type of polymorphism is called dominant.

    CalculateFineTotal Overrides Public Function () as double

        As Int32 = daysOverdue CalculateDaysOverdue (Sun)

        If daysOverdue> 0 Then

            Go daysOverdue 0,75

        Other

            0.0 Back

        End If

    End Function

 

End Class

Components involved in the PLO

Components: objects, classes (public, private), methods (public, private), variables (public, private), collectors' items are essential for the understanding of object-oriented technology. Look around and you'll find many examples of real-world objects: your dog, desk, TV, bicycle.

real objects have two characteristics: they all have state and behavior. Dogs are able to (name, color, breed, hungry) and behavior (barking, recovery, wagging his tail). Cycling is also (current speed, current pedal cadence, current speed) and behavior (gear, changing pedal cadence, applying brakes). State and behavior of objects in the real world is a great way to start thinking in terms of object-oriented programming.

Take a minute right to real-world objects in the vicinity to watch. For each element, you see, you ask two questions: "What could the possible states for this purpose" and make sure to write your comments: "What possible problem could object." . If you do, you'll notice that the real-world objects vary in complexity, your desk, only two possible states (on and off) and two possible behaviors (Turn, Turn), but your office may have different states of the radio (in, out, current volume, the current drive) and behavior (turn, turn, increase volume, decrease volume, scan and melody). You may also notice that some objects that turn other objects. These observations of real world translates into the world of object-oriented programming.

Bicycle modeled as a software object.

Assigning state (current speed, current pedal cadence, current and speed) and providing methods for changing this state of the object remains in control as the outside world are allowed. For example, if the bike is only 6-speed, method of changing the speed value is lower than 1 or greater than 6 reject.

Grouping the individual code of the software has several advantages, including:

1. Modularity: the source code of the object can be recorded and maintained regardless of the source code for other objects. Once created, the object can be easily moved throughout the system.

2. Information-hiding: By interacting only with the methods of the object, to keep the details of its internal implementation is hidden from the outside world.

3. reuse of code: If the object already exists (perhaps written by another software developer), you can object in your program. This allows technicians to perform / / debugging of complex objects that are specific to the tasks, then you trust your own code to run the tests.

4. Easy installation and debugging: if an object is a particular problem, you can request and simply remove the plug to another object as a replacement. This is analogous to solving mechanical problems in the real world. In the event of failure of the bolts to be replaced, but not the whole machine.

What is the class:

In the real world, you often find many individual objects of the same nature. There may be thousands of other bicycles in existence, all the same make and model. Each bike was built from the same set of plans and, therefore, contains the same ingredients. In connection with the object-oriented, we say that your bicycle is an instance of a class of objects known as cycling. Class template from which individual objects are created.

The next category of bikes is the possibility of bike:

class Bicycle {

       Int cadence = 0;

       Int speed = 0;

       Int gear = 1;

       changeCadence void (INT NewValue) {

            cadence = NewValue;

       }

       Gear void change (INT NewValue) {

            Speed = NewValue;

       }

       Void SpeedUp (INT gain) {

            Speed = speed increase;

       }

       Apply the brakes as invalid (INT below) {

            speed = speed - decrease;

       }

       Station void print () {

            System.out.println ("cadence:" speed "speed" speed "gear");

       }

}

The syntax of the Java programming language a new look at you, but the design of this class based on the earlier discussion of bicycle facilities. Rate of pitch, speed and acceleration of the object state and methods (changeCadence, switching speeds, etc.) as a means to determine their interaction with the outside world.

Class bicycle {demo

     public static void main (String [] args) {

          / / Create two different objects Bike

          Bike1 bike new bike = ();

          Bike2 Bike = New ();

          / / Call methods on these objects

          bike1.changeCadence (50);

          bike1.speedUp (10);

          bike1.changeGear (2);

          bike1.printStates ();

          bike2.changeCadence (50);

          bike2.speedUp (10);

          bike2.changeGear (2);

          bike2.changeCadence (40);

          bike2.speedUp (10);

          bike2.changeGear (3);

          bike2.printStates ();

     }

}

Exit this test prints the end of cadence, speed and equipment for the bike:

Speed: 50 Speed: 10 gears: 2

speed: 40 Speed: 20 Speed: 3

Variables

As you learned in the previous chapter, the object stores the state of the fields.

Int cadence = 0;

Int speed = 0;

Int gear = 1;

What is the purpose? discussion of field settings, but you probably have some questions: What are the rules and conventions for the naming of the field? Int Furthermore, what types of data than others? Add a field must be initialized when they report? fields get a default value if not explicitly initialized? We will explore answers to these questions in this lesson, but before we can, there are some technical differences you must know. In Java, the terms "domain" and "variable" are used equally, which is often a source of confusion for new developers, because the two often seems to refer to the same thing.

The Java programming language defines the types of variables:

• instance variables (non-static field) Technically speaking, the storage of individual objects, non-static fields of their states, that is, fields declared without the static keyword. Non-static fields, also known as instance variables because their values are specific to each instance of the class (each object, in other words), the current speed bike current speed independent of each other.

• Variable class (static fields) of the class variable region indicates the static modifier, the compiler that there is exactly one copy of this variable in existence told, no matter how many times the class was created. Field with the number of transmissions for a certain type of bike will be marked as stable with conceptually the same number of gears will be applied to all cases. NumGears static Int code = 6; create a static field. In addition, the final keyword can be added to indicate that the amount of equipment will never change.

• Local residents, just as object stores its state in fields, often using to store the temporary state in local variables. The syntax for declaring a local variable which is equal to the field (eg Int Count = 0). There is no special keyword destination variable, as local decision comes entirely from the place where the variable is declared - that lies between the opening and closing parentheses of the method. Thus, local variables are only available for methods that were declared, they are not accessible from the rest of the class.

• The settings you've already seen examples of parameters, both in the classroom, and a bicycle in the main method of "Hello World" application. Remember that the main method signature public static void main (String [] args). Here, the variable arguments to this method. It is important to remember that the parameters are always classified as "variable" rather than "field". This option applies to other buildings and to take (for example, builders and managers of exceptions), you will learn at the end of the textbook.

Nevertheless, the rest of this tutorial uses the following rules when considering the fields and variables. When we speak of "fields in general (except for local variables and parameters), we can simply say:" field, all the above, we can simply say: "variable" "In discussing the concerns.." If the context, the distinction, we use specific terms (static fields, local variables, etc.), if any. Sometimes you can see the term "member" are used together. Form fields, methods and nested types are collectively called its members.

Title

Each programming language has its own set of rules and conventions in the form of names that you have the right to use, and the Java programming language is no exception. Rules and conventions for naming variables can be summarized as follows:

• Variable names are case-sensitive. The variable name can be any legal identifier - a sequence of unlimited length Unicode letters and digits, beginning with the letter, a dollar sign "$" or the "_". The agreement is always your variable names start with the letter, rather than "$" or "_". In addition, the dollar sign, by convention, never used at all. Find a situation where the names of the independent organization, the dollar sign, but the variable names should avoid using them. A similar agreement exists for the underscore, and is technically legal to begin with the name of your variable with "_", this practice is discouraged. Spaces are not allowed.

• The following characters can be letters, numbers, dollar signs, or underscore. Conventions (and common sense) apply to this rule. When you call your variables to choose to use whole words rather than cryptic abbreviations. This will make your code easier to read and understand. In many cases it will also make your own code to the document, called the cadence of the field, velocity and acceleration, for example, is much more intuitive than abbreviated versions, such as S, C and G. Keep in mind that the name you choose, there should be a keyword or keyword.

• If the name you choose is made of a single word, written word in lowercase. If it consists of a few words below the first letter of each word. Names and gearratio current transmission are excellent examples of this Convention. If your variable stores a constant value, as NUM_GEARS static final Int = 6, the Convention of the changes, capitalize every letter and separate words with underscores. By convention, the underscore is not used elsewhere.

Determination methods

Here's an example declaration of the traditional method:

public double calculateAnswer (wingspan double Int numberOfEngines, double length, double gross registered tons) {

/ / Do calculation here

}

Only the necessary elements of the method declaration of a method that returns a name, a pair of brackets (), and body in braces {}.

In general, the method returns six parts, in order:

1. Modifiers, such as public, private, and others, you will learn later.

2. Return type of the data type of the return value of method, or null if the method returns no value.

3. The name of the method of "rules of the domain refers to the method names as well, but the Convention is a little different.

4. Parameter list in parentheses, a comma separated list of input parameters, preceded by their data types, separated by parentheses (). If there are no parameters, you need parentheses.

5. The list of exceptions that will be discussed later.

6. The method body lift method code, including the declaration of local variables goes here.

Naming Method

Even if the method name can be any legal identifier code conventions to limit the method names. By convention, method names must be lowercase verb or multi-word name that starts with a lowercase verb, then adjectives, nouns, etc. In the name of several words, the first letter of each half and after the word must be capitalized. Here are some examples:

Run

RUNFASTER

getBackground

getFinalData

CompareTo

set X

IsEmpty

Typically, the method has a unique name in its category. However, this method have the same name as the other methods because the method of overload.

Overloading Methods

The Java programming language supports method overloading, and Java can distinguish between methods with different method signature. This means that the methods in the class may have the same name, as they have a list of options (there are some caveats to be discussed in class, entitled "Interfaces and Inheritance").

Suppose you have a class that you can use calligraphy to attract different types of data (strings, numbers, etc.) and a method for each type of data to pull. Difficult new name for each method, for example, draw string, integer, draw, draw, swim, and so on. In the programming language Java, you can use the same name for all drawing techniques, but there is another list of arguments for each method. Thus, the data for drawing class to explain the four methods named draw, each with a different parameter list.

Data {People's Artist of the class

...

public void draw (String S) {

...

}

public void draw (Int I) {

...

}

public void draw (double F) {

...

}

public void draw (INT I double F) {

...

}

}

Overloaded methods differ in the number and nature of the arguments that are passed into the method. The code sample, draw (String) and set (Int I) are separate and unique ways as they require different kinds of arguments.

You can not explain more than one method with the same name and number and type of arguments because the compiler can not distinguish

Writing Services

Essay Writing
Service

Find out how the very best essay writing service can help you accomplish more and achieve higher marks today.

Assignment Writing Service

From complicated assignments to tricky tasks, our experts can tackle virtually any question thrown at them.

Dissertation Writing Service

A dissertation (also known as a thesis or research project) is probably the most important piece of work for any student! From full dissertations to individual chapters, we’re on hand to support you.

Coursework Writing Service

Our expert qualified writers can help you get your coursework right first time, every time.

Dissertation Proposal Service

The first step to completing a dissertation is to create a proposal that talks about what you wish to do. Our experts can design suitable methodologies - perfect to help you get started with a dissertation.

Report Writing
Service

Reports for any audience. Perfectly structured, professionally written, and tailored to suit your exact requirements.

Essay Skeleton Answer Service

If you’re just looking for some help to get started on an essay, our outline service provides you with a perfect essay plan.

Marking & Proofreading Service

Not sure if your work is hitting the mark? Struggling to get feedback from your lecturer? Our premium marking service was created just for you - get the feedback you deserve now.

Exam Revision
Service

Exams can be one of the most stressful experiences you’ll ever have! Revision is key, and we’re here to help. With custom created revision notes and exam answers, you’ll never feel underprepared again.