Introduction to UML Lian Yu Department of Computer Science and Engineering Arizona State University...

Introduction to UML

Lian YuDepartment of Computer Science and EngineeringArizona State UniversityTempe, AZ 85259

UML, UML Diagrams

UML stands for the Unified Modeling Language

UML diagrams show/visualize relationships among classes and objects

Several types of UML diagrams exist, each designed to show specific aspects of object-oriented program design

Class Diagram

A UML class diagram consists of one or more classes, each with sections for the class name, attributes, and methods

Depending on the goal of the diagram, the attribute and/or methods sections can be left out of any class

Lines between classes represent associations

Associations/aggregation can show multiplicity

Class Diagram

Attributes and methods may be marked as: Private, indicating they are not visible to callers outside

the class Protected, they are only visible to children of the class Public, they are visible to all

Symbol Meaning

+

-

#

Public

Private

Protected

UML Class Diagrams

A UML class diagram for the FlipRace program:

FlipRace

main (args : String[]) : void

Coin

face : int

flip() : voidisHeads() : booleantoString() : String

1 2

Object Diagram

A UML object diagram consists of one or more instantiated objects.

It is a snapshot of the objects during an executing program, showing data values

coin1 : Coin

face = 0

coin2 : Coin

face = 1

Association in UML

Two classes having a general associationThose classes are “aware” of each

otherObjects of those classes may use

each other for the specific servicesThis sometimes is referred to as a use

relationship

Association

When a class participates in an association, it has a specific role that it plays in that relationship

A role is just the face the class at the near end of the association presents to the class at the other end of the association.

Person Company+employer+emplyee

association

role name

Aggregation in UML

An aggregate object is an object that contains references to other objects

For example, an Account object contains a reference to a String object (the owner's name)

An aggregate object represents a has-a relationship

A bank account has a name Likewise, a student may have one or more

addresses

Aggregation in UML

An aggregation association is shown in a UML class diagram using an open diamond at the aggregate end

StudentBody

+ main (args : String[]) : void

+ toString() : String

1 2Student- firstName : String

- lastName : String- homeAddress : Address- schoolAddress : Address

+ toString() : String

- streetAddress : String- city : String- state : String- zipCode : long

Address

Tools to Draw UML Diagrams

Microsoft Visio Rational Rose