BCS 2143

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BCS 2143

• Object Oriented Design Using UML

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Objectives

• Objects Interactions
• Finding Classes
• Relationship Between Classes
• Attribute and Operation
• Class Diagram

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Outline

• Name the basic components of object-oriented
  design using UML
• Experience with significant diagram in UML
• Experience with main part of class that consists
  of attributes and operation
• Class Diagram association, aggregation and
  inheritance
• Basic concepts in Sequence Diagram
• Utilize all modeling concepts in solving problem

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Unified Modeling Language

• UML - standardized general-purpose modeling
  language in the field of software engineering
  using graphical notations
• UML Diagrams
• Use Case Diagram
• Class Diagram
• Interaction Diagram
• Component Diagram
• Etc.

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UML 2.0
Emphasizes the dynamic behavior of the system by
showing collaborations among objects and changes
to the internal states of objects
Emphasizes the static structure of the system
using objects, attributes, operations and
relationships
UML 2.0 has 13 types of diagrams divided into
three categories. Six diagram types represent the
structure application, seven represent general
types of behavior, including four that represent
different aspects of interactions.
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Use Case Diagram

• System behavior how the system act and react
  towards their environment.
• Consists of
• Actor represent environment of system
• Use case represent function of system

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Example of Use Case Diagram for ATM Machine
Customer
Make transaction
Manage bank transaction
Bank Clerk
Bank
Produce report
ATM Maintainer
Maintain ATM Machine
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Class Diagram

• Diagram that consists of several classes or
  objects.
• Object
• represent specific entity in term of physical and
  conceptual
• have the behaviors, characteristics and identity
• Class
• Represent a group of object that have the similar
  attribute, behavior and relationship among the
  others

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Example of Class Diagram

• Class diagram describes the structure of a
  system by showing the system's classes, their
  attributes, and the relationships among the
  classes.

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Interaction Diagram

• Represent string of messages that have been
  submit and receive and its relation
• Example of 2 types
• Sequence diagram based on sequence of time
  frame
• Collaboration diagram represent the data flow

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Sequence Diagram
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Collaboration Diagram
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Classes and Objects

• Object-oriented programs use objects.
• An object is a thing, both tangible and
  intangible. Account, Vehicle, Employee, etc.
• To create an object inside the computer program,
  we must provide a definition for objectshow they
  behave and what kinds of information they
  maintain called a class.
• An object is called an instance of a class.

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Graphical Representation of a Class
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Graphical Representation of an Object
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An Object with the Class Name
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Messages and Methods

• To instruct a class or an object to perform a
  task, we send a message to it.
• A class or an object must possess a matching
  method to be able to handle the received message.
• A method defined for a class is called a class
  method, and a method defined for an object is
  called an instance method.
• A value we pass to an object when sending a
  message is called an argument of the message.

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Sending a Message
myWindow.setVisible(true) personA.deposit( 250.0
) student.setName(john) car1.startEngine( )
Examples
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Sending a Message and Getting an Answer
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Calling a Class Method
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Class and Instance Data Values

• An object is comprised of data values and
  methods.
• An instance data value is used to maintain
  information specific to individual instances. For
  example, each BankAccount object maintains its
  balance.
• A class data value is used to maintain
  information shared by all instances or aggregate
  information about the instances.
• For example, minimum balance is the information
  shared by all Account objects, whereas the
  average balance of all BankAccount objects is an
  aggregate information.

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Sample Instance Data Value
All three BankAccount objects possess the same
instance data value current balance.
The actual dollar amounts are, of course,
different.
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Sample Class Data Value
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Object Icon with Class Data Value
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Class

• Class name
• Start with capital letter for each new word
• Example Student, StudentAdvisory
• Attributes
• Represent the characteristics of the object
• Variables,
• Operation
• Represent the behavior of the class
• Methods, behaviors

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Class/Attribute/Method/Object
Student
Class
name age course fees
Attribute (variable)
registerSubject withdrawSubject borrowBook
Method (operation)
Object
Object
StdDiploma
Std1
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Java Code Class, Attribute, Method Declaration
public class Student // class name String
name // attribute _at_ variable
declaration int age 10 String course
DCS double fees 1067.60 public void
registerSubject () // code for
register subject
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Java Code Object Declaration / Manipulation
public Class Student public static
void main (String data) Student
stdDiploma // declaring/creating an object
stdDiploma new Student() // object
initialize Student Std1 new Student()
// declaration and initialize
Std1.name " Amad // assigning value to
object Std1.age 24 // assigning value
to object System.out.println(" student name
" Std1.name) System.out.println("
student age registration " Std1.age)

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Relationships among Classes

• Association
• Aggregation
• Composition
• Inheritance

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Association

• Association represents a general binary
  relationship that describes an activity between
  two classes.

An association is usually represented as a data
field in the class.
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Aggregation

• Whole-to-part associations
• The concept representing the whole is called the
  aggregate each concept representing a part is
  called constituent.
• The aggregate and the constituent may existed
  independently of each other.

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Example of Aggregation
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Composition

• Whole-to-part associations
• The concept representing the whole is called the
  composite each concept representing a part is
  called component
• The composite does not exist independently from
  its component
• The component may exist without the composite

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Example of Composition
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Aggregation vs Composition
AGGREGATION COMPOSITION
Name of whole Aggregate Composite
Name of part Constituent Component
Parts May be different types Usually the same type
Existence May exist without its parts Does not exist without its parts
Number of wholes to which a part may belong Part may belong to more than one aggregate at a time Part may belong to only one composite at a time
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Inheritance

• Inheritance is a mechanism in OOP to design two
  or more entities that are different but share
  many common features.
• Features common to all classes are defined in the
  superclass.
• The classes that inherit common features from the
  superclass are called subclasses.
• We also call the superclass an ancestor and the
  subclass a descendant.

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A Sample of Inheritance

• Here are the superclass Vehicle and its
  subclasses Car, Boat and Truck.

Truck
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Inheritance

• Inheritance models the is-an-extension-of
  relationship between two classes.

public class Car extends Vehicle / Data
fields / / Constructors / / Methods
/ public class Boat extends Vehicle /
Data fields / / Constructors / /
Methods /
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Inheritance Hierarchy

• An example of inheritance hierarchy among
  different types of students.

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Example of class diagram with multiplicities,
attributes and operations
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Key Concepts

• Variable
• Constant
• Inheritance
• Superclass
• Subclass

• OOP
• Class
• Object
• Message
• Class and instance methods
• Instance and class data values

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Q A