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