Object-Oriented Concepts Overview - PowerPoint Presentation

							   Florida Community College at Jacksonville




             Object-Oriented Concepts
                                  Overview




COP 2551 Object-Oriented Programming           Spring,2003
  Florida Community College at Jacksonville



                                   Objective
     • Overview of Object Orientation
     • Object Attributes and Operations
     • Difference between an object and a class
     • 3 basic Object-oriented principles (Encapsulation,
       Inheritance and Polymorphism)
     • Reference: Thinking in Java (Bruce Eckel)
          Free download @http://www.BruceEckel.com

COP 2551 Object-Oriented Programming          OO Concepts Overview   2 of 10 slides
  Florida Community College at Jacksonville

     Overview of Object Orientation
     •    Object orientation is a technique for system modeling, Object
          oriented analysis and design, or OOAD, attempts to describe
          a system as it exists in real life.
     •    The system is modeled as a number of related objects that
          interact. Any system needs objects to do work. It “asks” its
          objects to do its work, just as you might ask objects in an
          online store to deliver goods to you and charge the cost to
          your credit card.
     •    All objects have attributes (characteristics), this is sometimes
          referred to as state.
     •    They also have operations (or methods), this is sometimes
          referred to as behavior.
COP 2551 Object-Oriented Programming          OO Concepts Overview   3 of 10 slides
  Florida Community College at Jacksonville



                    Examples of Objects
    Use an online store (such as amazon.com) as an
      example, the following things may consider as
      Objects:
    • Book
    • Customer
    • Order



COP 2551 Object-Oriented Programming          OO Concepts Overview   4 of 10 slides
  Florida Community College at Jacksonville



    Object Attributes and Operations
    • Attributes know something (Attributes are often
      data, like order ID and customer ID for an Order
      object. Attributes can also be another object, such as
      the entire Customer object rather than just the
      customer ID.
    • Operations do something with what the attributes
      know, (Operations can be actions that the object
      does, often affecting its attributes.)


COP 2551 Object-Oriented Programming          OO Concepts Overview   5 of 10 slides
  Florida Community College at Jacksonville


      Difference Between Object And
                   Class
     • A class is how you define an object. Classes are
       descriptive categories or templates. Book could be a
       class.
     • Objects are unique instances of classes. This Java
       Certification book that costs $59.99 with item ID
       62467-B is an object of the Book class.



COP 2551 Object-Oriented Programming          OO Concepts Overview   6 of 10 slides
  Florida Community College at Jacksonville


         Difference Between Object And
                 Class (continue)
     •    The attributes and operations defined by a class are for its
          objects, not for itself. There is no concrete realization of the
          class Book, but there are Book objects, i.e. a class is a logical
          construct, an object has physical reality.
     •    A class can be compared to a blueprint. Imagine you are in
          charge of building a housing development, with one housing
          blueprint. Each house in a development is shaped the same
          way, but some have brick or aluminum siding, some have
          custom paint colors inside and some are just white, and so on.

COP 2551 Object-Oriented Programming          OO Concepts Overview   7 of 10 slides
  Florida Community College at Jacksonville


             Object-oriented Principle –
                    Encapsulation
     • Encapsulation is the mechanism that binds together
       the code and the data it manipulates, and keeps both
       safe from outside interference and misuse.

                        Public variables and methods                    A Class

                                Private variables
                                and methods
                 Public variables is not recommended
COP 2551 Object-Oriented Programming          OO Concepts Overview   8 of 10 slides
  Florida Community College at Jacksonville


             Object-oriented Principle -
                     Inheritance
     • Inheritance is the process by which one object
       acquires the properties of another object. By use of
       inheritance, an object need only define all of its
       characteristics that make it unique within its class, it
       can inherit its general attributes from its parent.
                                       Account

                Checking               Mortgage            Loan

COP 2551 Object-Oriented Programming          OO Concepts Overview   9 of 10 slides
  Florida Community College at Jacksonville


             Object-oriented Principle –
                    Polymorphism
     • Polymorphism(from Greek, meaning“many forms”)
       is a feature that allows one interface to be used for a
       general class of actions, i.e. one interface, multiple
       methods.
     • Example: Account.calculateInterest()




COP 2551 Object-Oriented Programming          OO Concepts Overview   10 of 10 slides