CMSC 132:
Object-Oriented Programming II
Nelson Padua-Perez
William Pugh
Department of Computer Science
University of Maryland, College Park
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UML Class Diagrams: Understanding Object-Oriented Programming II with Java - Prof. Nelson , Study notes of Computer Science
An overview of uml (unified modeling language) class diagrams, focusing on java programming. It explains the different types of relationships between classes, such as association, dependency, and generalization, and their notation. It also covers the concept of multiplicity and its notation. Examples of uml class diagrams for various systems, such as veterinary, computer, banking, and home heating systems, and provides instructions on how to derive java code from uml class diagrams and vice versa.
Typology: Study notes
Pre 2010
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CMSC 132:
Object-Oriented Programming II
Nelson Padua-Perez
William Pugh
Department of Computer Science
University of Maryland, College Park
UML Class Diagrams
Represent the (static) structure of the system General
In Java
Name
Name
State
Variables
Behavior
Methods
Association
Denotes permanent, structural relationship State of class A contains class B Represented by solid line (arrowhead optional)
Car
and
Engine
classes know about each other
Associations w/ Navigation Information
Can indicate direction of relationship Represented by solid line with arrowhead
Gas Pedal
class knows about
Engine
class
Engine
class doesn’t know about
Gas Pedal class
Multiplicity of Associations
Some relationships may be quantified Multiplicity denotes how many objects thesource object can legitimately reference Notation
0, 1, or more
5 exactly
between 5 and 8, inclusive
5 or more
Multiplicity of Associations
Many-to-one
Bank has many ATMs, ATM knows only 1 bank
One-to-many
Inventory has many items, items know 1 inventory
Dependency
Caused by class methods Method in Class
A
temporarily “
uses a
” object
of type Class
B
Change in Class
B
may affect class
A
A uses object of class 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 B();
return y;
Generalization
Denotes
inheritance
between classes
Can view as “
is-a
” relationship
Represented by line ending in (open) triangle
Laptop, Desktop, PDA inherit
state & behavior from Computers
Implementation
Denotes class
implements
Java interface
Represented by dotted line ending in (open)triangle
A implements interface B
A
«B»
UML Example – Veterinary System
Try to read & understand UML diagram
UML Example – Veterinary System
Try to read & understand UML diagram
1 or more Pets associated with 1 PetOwner
UML Example – Computer System
Try to read & understand UML diagram
1 CPU associated with 0 or more Controllers
1-4 DiskDrives associated with 1 SCSIController
SCSIController is a (specialized) Controller
UML Example – Banking System