OO & UML

UML
uniﬁed model language
model / design / documentation /
understand legacy code
communication

Table 1.1. Official Diagram Types of the UML
Book
文本文本
[3]
UML diagram category

our topic
class diagram
sequence diagram
activity diagram
oo/design pattern

class diagram
describe the classes and their relationship
within the system

class diagram
class itself
class relationship
inheritance
dependency

class (itself)
pictures are captured from [apply UML & pattern]
class type
method
return/params
static/abstract
attribution visibility

class type(map java/c++)
interface
abstract class
{concrete} class
class with all pure virtual methods
class with some virtual methods
classwith no virtual methods
C++JavaUML
interface
abstract class
{concrete} class

class relationship UML
interface
implementation
composition
association
generalization

class relationship
generalization =~ subtype -> extends :
interface implementation -> implements :
UML Java C++

! ! 2 type of inheritance
interface inheritance
IC extends IA ,IB
CA implements IA
CD extends CA
CD extends CA implements CB
implementation
inheritance
Item 16, [5]

The ArrayList itself is a subclass of the AbstractList class. AbstractList provides some, but not
all, the implementation of the List behavior. In particular, the get method is abstract. As a result,
ArrayList implements get but also overrides some of the other operations on AbstractList. In
this case, it overrides add but is happy to inherit the implementation of equals.
Example
extends
extends
implements

dependency
dependency -local, parameters,static method
association - attribution
aggregation - whole-part relationship
composition - non-shared aggregation
A dependency exists between two elements if changes to the definition of
one element (the supplier) may cause changes to the other (the client).
stronger
weaker

example
65/118
Aggregation and Composition
One of the most frequent sources of confusion in the UML is aggregation and composition. It's
to explain glibly: Aggregation is the part-of relationship. It's like saying that a car has an eng
and wheels as its parts. This sounds good, but the difficult thing is considering what the differe
between aggregation and association.
In the pre-UML days, people were usually rather vague on what was aggregation and what wa
association. Whether vague or not, they were always inconsistent with everyone else. As a res
many modelers think that aggregation is important, although for different reasons. So the UML
included aggregation (Figure 5.3) but with hardly any semantics. As Jim Rumbaugh says, "Thin
as a modeling placebo" [Rumbaugh, UML Reference].
Figure 5.3. Aggregation
As well as aggregation, the UML has the more defined property of composition. In Figure
instance of Point may be part of a polygon or may be the center of a circle, but it cannot b
The general rule is that, although a class may be a component of many other classes, any
must be a component of only one owner. The class diagram may show multiple classes of
owners, but any instance has only a single object as its owner.
Figure 5.4. Composition
You'll note that I don't show the reverse multiplicities in Figure 5.4. In most cases, as here
Its only other possible value is 1, for cases in which the component class is designed so th
have only one other class as its owner.
The "no sharing" rule is the key to composition. Another assumption is that if you delete th
polygon, it should automatically ensure that any owned Points also are deleted.
Composition is a good way of showing properties that own by value, properties to value ob
(page 73), or properties that have a strong and somewhat exclusive ownership of particula
components. Aggregation is strictly meaningless; as a result, I recommend that you ignore
own diagrams. If you see it in other people's diagrams, you'll need to dig deeper to find ou
they mean by it. Different authors and teams use it for very different purposes.
Derived Properties
37/118
discuss other visibilities on page 83.
• The name of the attribute—how the class refers to the attribute—roughly corresponds to the
name of a field in a programming language.
• The type of the attribute indicates a restriction on what kind of object may be placed in the
attribute. You can think of this as the type of a field in a programming language.
• I'll explain multiplicity on page 38.
• The default value is the value for a newly created object if the attribute isn't specified
during creation.
• The {property-string} allows you to indicate additional properties for the attribute. In the
example, I used {readOnly} to indicate that clients may not modify the property. If this is
missing, you can usually assume that the attribute is modifiable. I'll describe other property
strings as we go.
Associations
The other way to notate a property is as an association. Much of the same information that you can
show on an attribute appears on an association. Figures 3.2 and 3.3 show the same properties
represented in the two different notations.
Figure 3.2. Showing properties of an order as attributes
Figure 3.3. Showing properties of an order as associations
An association is a solid line between two classes, directed from the source class to the target
class. The name of the property goes at the target end of the association, together with its
multiplicity. The target end of the association links to the class that is the type of the property.
association
[3]

don’t bother use aggregation, use
composition when appropriate.
[1][4]
use association for normal attribution,
use aggregation for collection of attribution

FYI[3]
65/118
Static Operations and Attributes
The UML refers to an operation or an attribute that applies to a class rather than to an instance as
static. This is equivalent to static members in C-based languages. Static features are underlined on
a class diagram (see Figure 5.2).
Figure 5.2. Static notation
Aggregation and Composition
One of the most frequent sources of confusion in the UML is aggregation and composition. It's easy
to explain glibly: Aggregation is the part-of relationship. It's like saying that a car has an engine
and wheels as its parts. This sounds good, but the difficult thing is considering what the difference is
between aggregation and association.
In the pre-UML days, people were usually rather vague on what was aggregation and what was
association. Whether vague or not, they were always inconsistent with everyone else. As a result,
many modelers think that aggregation is important, although for different reasons. So the UML
included aggregation (Figure 5.3) but with hardly any semantics. As Jim Rumbaugh says, "Think of it
as a modeling placebo" [Rumbaugh, UML Reference].
Figure 5.3. Aggregation
As well as aggregation, the UML has the more defined property of composition. In Figure 5.4, an
instance of Point may be part of a polygon or may be the center of a circle, but it cannot be both.
The general rule is that, although a class may be a component of many other classes, any instance
must be a component of only one owner. The class diagram may show multiple classes of potential
You'll note that I don't show the reverse multiplicities in Figure 5.4. In most cases, as here, it's 0..1.
Its only other possible value is 1, for cases in which the component class is designed so that it can
The "no sharing" rule is the key to composition. Another assumption is that if you delete the
Composition is a good way of showing properties that own by value, properties to value objects
(page 73), or properties that have a strong and somewhat exclusive ownership of particular other
components. Aggregation is strictly meaningless; as a result, I recommend that you ignore it in your
own diagrams. If you see it in other people's diagrams, you'll need to dig deeper to find out what
Derived Properties
As well as aggregation, the UML has the more defined property of composition. In Figure 5.4, an
instance of Point may be part of a polygon or may be the center of a circle, but it cannot be both.
The general rule is that, although a class may be a component of many other classes, any instance
must be a component of only one owner. The class diagram may show multiple classes of potential
You'll note that I don't show the reverse multiplicities in Figure 5.4. In most cases, as here, it's 0..1.
Its only other possible value is 1, for cases in which the component class is designed so that it can
The "no sharing" rule is the key to composition. Another assumption is that if you delete the
Composition is a good way of showing properties that own by value, properties to value objects
(page 73), or properties that have a strong and somewhat exclusive ownership of particular other
components. Aggregation is strictly meaningless; as a result, I recommend that you ignore it in your
own diagrams. If you see it in other people's diagrams, you'll need to dig deeper to find out what
Derived Properties
Derived properties can be calculated based on other values. When we think about a date range
(Figure 5.5), we can think of three properties: the start date, the end date, and the number of days
in the period. These values are linked, so we can think of the length as being derived from the other
two values.
Figure 5.5. Derived attribute in a time period

wrap up example
A class diagram describes the types of objects in the system and the various kinds of static
relationships that exist among them. Class diagrams also show the properties and operations of a
class and the constraints that apply to the way objects are connected. The UML uses the term
feature as a general term that covers properties and operations of a class.
Figure 3.1 shows a simple class model that would not surprise anyone who has worked with order
processing. The boxes in the diagram are classes, which are divided into three compartments: the
name of the class (in bold), its attributes, and its operations. Figure 3.1 also shows two kinds of
relationships between classes: associations and generalizations.
Figure 3.1. A simple class diagram
Properties
Properties represent structural features of a class. As a first approximation, you can think of
properties as corresponding to fields in a class. The reality is rather involved, as we shall see, but
that's a reasonable place to start.

advice
class diagram is the backbone of UML, so
familiar yourself with it
focus on big picture
use it with sequence diagram

sequence diagram
describe object interaction in speciﬁc user
case

sample
pic taken from [1]
sync call
async call
obj:Type
activation box

Activity Diagram
OO equivalent of ﬂowchart in structured dev.
With addition support for concurrency
Use it describe business logic or complex algorithm

OOD, Patterns & UML
UML express your OOD
Good OOD follow OOD principle
Design Pattern = proven OOD solution

DIP
dependency inversion principle

DIP
[8]
List list = new ArrayList();

DIP - strategy pattern
programming to interface not implementation

Template Method
Hollywood principle : don’t call me , I will call you.

reference
1.apply UML & pattern , Craig Larman
2.design pattern, GOF
3.UML distilled ,Martin Fowler
4. Agile software development, Bob Martin
5. Effective Java , Joshua Bloch
6.http://en.wikipedia.org/wiki/Solid_(object-oriented_design)
7.http://www.visual-paradigm.com/VPGallery/diagrams/Activity.html
8.http://www.objectmentor.com/resources/articles/dip.pdf
9.http://exciton.cs.rice.edu/javaresources/DesignPatterns/

OO & UML

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