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CMSC 132:
Object-Oriented Programming II
Unified Modeling Language
(UML)
Department of Computer Science
University of Maryland, College Park
UML (Unified Modeling Language)
UML is a modeling language for
Specifying Visualizing Constructing Documenting
object-oriented software
Motivation
Software growing larger & complex
Difficult to describe and analyze
Use UML to help
Visualize design of software Provide abstract model of software
Goals
Provide a software “blueprint”
Simple yet clear abstraction for software
Describe software design
Clearly Concisely Correctly
History of UML
Started in 1994
Combines 3 leading OO methods
OMT (James Rumbaugh) OOSE (Ivar Jacobson) Booch (Grady Booch)
UML Diagrams
UML provides a number of diagrams that
Describe a model of all or part of system From a particular point of view With varying level of abstraction Using certain set of notations
System Model 1
Model 2
View 1 View 3
View 2
Class Diagram
Represents (static) structure of system
A class diagram displays
Information for class Relationships between classes
Class Diagram
Batteryload()
1 2 PushButtonstate Timenow() push()release()
1 1
1 1
1 2 blinkIdxblinkSeconds() blinkMinutes()blinkHours() stopBlinking()referesh()
LCDDisplay
SimpleWatch
Class
Multiplicity Association
Attributes Operations
Class diagrams represent structure of system
Class Diagrams
Information for class contains
Name State Behavior
Class Diagram
Class name is required
Other information optional
State, behavior Types, visibility…
UML Class Diagrams ↔ Java Code
Different representation of same information
Name, state, behavior of class Relationships between classes
Should be able to derive one from the other
Motivation
UML ⇒ Java Implement code based on design written in UML Java ⇒ UML Create UML to document design of existing code
Java → UML : Clock Example
Java
class Clock { // name // state int seconds; int minutes; int hours; // behavior void start(); void adjustTime(); void reset(); }
Java Code Class Diagram
Association w/ Navigation
Navigation information
Relationship between classes may be directional Only class A can send messages to class B Arrowhead indicates direction of relationship
Example
class Course { class Lecturer { Lecturer TheBoss; … } }
Association w/o Navigation
Undirected edge
Relationship between classes may be bi-directional Direction of relationship may be unknown
Examples
class Course { class Lecturer { Lecturer TheBoss; Course [ ] class; } }
class Foo class Bar
Permanent Association
Permanent / structural association
Class A contains reference to class B in data field Can view as “has a” relationship Also referred to as composition
Example
class A { class B { B x; … } }
A has a B
Temporary Association (Dependency)
A transitory relationship between classes
Always directed (class A depends on B) Indicates change in class B may affect class A Can view as “uses a” relationship Represented by dotted line with arrowhead
Example
A depends on B
A B
Dependency
Dependence may be caused by
Local variable Parameter Return value
Example
class A { class B { B foo(B x) { … B y = new( ); … … … } } }
UML Examples
Read UML class diagram
Try to understand relationships Practice converting to / from Java code
Examples
Computer disk organization Banking system Home heating system Printing system
UML Example – Computer System
Try to read & understand UML diagram
- CPU is associated with Controllers
- DiskDrive is associated with SCSIController
- SCSIController is a (type of) Controller
UML Example – Banking System
- Bank associated with Accounts
- Checking, Savings, MoneyMarket are type of Accounts
UML Example – Home Heating System
- Thermostat associated with (has a) Room
- Thermostat associated with (has a) Heater
- ElectricHeater is a specialized Heater
- AubeTH101D is a specialized Thermostat
UML Example – Library System
Try to read & understand UML diagram
- Books are associated with (has some) Pages
- Patron & Shelf depend on (temporarily use) Books
UML → Java : Computer System
UML
Java
class Controller { } class SCSIController extends Controller { }
UML → Java : Computer System
UML
Java
Design code using all available information in UML…
Amateras UML Editor – Eclipse Plugin Violet UML Editor
Drag-n-drop classes
into UML diagram
Auto creates class w/ attributes & methods
Add links manually
No undirected associations Use directed association in both directions instead
Violet UML Editor – Eclipse Plugin UML Summary
UML → modeling language
Visually represents design of software system
We focused on class diagrams
Contents of a class Relationship between classes
You should be able to
Draw UML class diagram given Java code Write Java code given UML class diagram
