2014
OOP-LECTURE 5
Object-Oriented Languages:
There are several object-oriented programming languages available to choose from,
including Smalltalk, Eiffel, C++, Objective C, Objective Pascal, Java, Ada, and even a
version of Lisp. There are two clear marketplace winners, C++ and Java.
Today, Java is the developing object-oriented language of choice for many
programmers and software projects.
One of the main reasons for Java's development is
 The World Wide Web and Java's ability to run web applets directly on any
computer or operating system with a web browser.
 Another reason is that Java is an excellent programming language. It is a small,
well-designed language that can be used for not just web applets, but
programs on almost any computer available today. Java was somewhat
hampered in its early days because of its speed, but this is really no longer an
issue.
 Because it is such a good language, Java has been widely adopted as the main
language used to teach computer science at colleges and universities all over
the world.
 In the whole history of computer science and programming, this is the first
time that the same programming language has been popular as both a
teaching language and a language used for real world programs.
Object-Oriented Modeling Using Unified Modeling Language (UML):
The Unified Modeling Language (UML) is a general-purpose modeling language in
the field of software engineering. The basic level provides a set of graphic notation
techniques to create visual models of object-oriented software-intensive systems.
Higher levels cover process-oriented views of a system.
What is a Model?
A model is a simplification of reality.
A successful software organization is one that consistently deploys quality software
that meets the needs of its users. An organization that can develop such software in
a timely and predictable fashion, with an efficient and effective use of resources,
both human and material, is one that has supportable business.”
We build models so that we can see and better understand the system we are
developing.
• Two most common ways in modeling software systems are
– Algorithmic
• Procedures or functions
Assistant Lecturer: Hawraa Shareef
62
2014
OOP-LECTURE 5
– Object oriented
• Objects or classes
• UML is a language for
– Visualizing
– Specifying
– Constructing
– Documenting
Interpretation in the Real World
Interpretation in the Model
Object
An object is a thing that can be
clearly identified.
An object has an identity,
a state, and a behavior.
Class
A class represents a set of
objects with similar
characteristics and behavior.
This objects are called the
instances of the class.
A class characterizes the structure
of states , and behaviors that are
shared by all instances.
• Each of object has a unique identity.
• The state of an object is composed of a set of fields (data fields), or
attributes.
• Each field has a name, a type, and a value.
• Behaviors are defined by methods.
• Each method has a name, a type, and a value.
• Each method may or may not return a value.
• Features are a combination of the state and the behavior of the object
• A class defines a template for creating its instances or objects.
• A class is a description of a set of objects that share the same attributes,
operations, relationships, and semantics
• A class defines-- the names and types of all fields the names, types,
implementations of all methods
Assistant Lecturer: Hawraa Shareef
62
2014
•
•
•
•
Example
OOP-LECTURE 5
The values of the fields are not defined or fixed in the class definition.
The values of the fields are mutable.
Each instance of the class has its own state.
Different instances of the class may have different states.
Class name: Point class Point {
Fields:
x, y
Method:
move
int x, y;
public void move
(int dx, int dy){
// implementation
}
UML Notation for Classes:
ClassName
The top compartment shows the class
name.
field
1
The middle compartment contains the
declarations of the fields of the class.
…
field
n
method
1
The bottom compartment contains the
declarations of the methods
…
method
m
Field Declaration:
• The name of the field is required in the field declaration.
• Field declaration may include:
•
[Visibility][Type]Name =[Initial Value]
• Visibility or accessibility defines the scope:
– Public -- the feature is accessible to any class
Assistant Lecturer: Hawraa Shareef
62
2014
OOP-LECTURE 5
– Protected -- the feature is accessible to the class itself, all the
7classes in the same package, and all its subclasses.
– Package -- the feature is accessible to the class itself and all
classes in the same package.
– Private -- the feature is only accessible within the class itself.
–
Visibility syntax in Java and UML:
Visibilty
Java Syntax
public
public
protected
protected
UML Syntax
+
#
package
~
private
private
-
Examples:
Java Syntax
UML Syntax
Date birthday
Birthday:Date
Public int duration = 100
+duration:int = 100
Private Student
students[0..MAX_Size]
-students[0..MAX_Size]:Student
Assistant Lecturer: Hawraa Shareef
62
2014
OOP-LECTURE 5
Method Declaration:
• The name of the method is required in the method declaration.
• Method declaration may include:
[Visibility][Type]Name([Parameter, ...])
[Visibility]Name([Parameter, ...])[:Type]
• Each parameter of a method can be specified by -- Type Name
Java Syntax
UML Syntax
void move(int dx, int dy)
~move(int dx, int dy)
public int getSize()
+int getSize()
Point
Point
private int x
private int y
-x:int
-y:int
public void move(int dx,int
dy)
+move(dx:int,dy:int)
Assistant Lecturer: Hawraa Shareef
03
2014
OOP-LECTURE 5
UML Notation for Object
ObjectName : ClassName
field1 = value1
The top compartment shows the
object name and its class.
The bottom compartment contains a
list of the fields and their values.
…
fieldn = valuen
objectName -- objectName whose class is of no interest
:ClassName -- anonymous object of ClassName which can be identify only through its
relationship with other object.
Examples
P1:Point
Point p1 = new Point();
x=0
p1.x = 0;
y=0
P1.y = 0;
P1:Point
x = 24
y = 40
Assistant Lecturer: Hawraa Shareef
Point p1 = new Point();
p1.x = 24;
P1.y = 40;
03