object-oriented programme 1 ssd3: object-oriented programming and design

Object-Oriented Programme Object-Oriented Programme 11

SSD3: Object-Oriented Programming and SSD3: Object-Oriented Programming and Design Design


1.1 Review of Java Basics 1.2 Java Application 1.3 Designing Classes

Unit 1. Class DesignUnit 1. Class Design


1.3 Designing Classes1.3 Designing Classes

Contents 1.3.1 UML Class Diagrams 1.3.2 Relationships Between Classes 1.3.3 Common Class Structures 1.3.4 UML with Eclipse 1.3.5 Modeling Classes 1.3.6 Modeling the Library System

Assessments Practical Quiz 3 Practical Quiz 4 Multiple-Choice Quiz 2 Exercise 2


1.31.3.1 UML Class Diagrams .1 UML Class Diagrams

Introduction Class Notation


IntroductionIntroduction

The Unified Modeling Language (UML, 统一建模语言 ) is a graphical language for modeling the static and dynamical aspects of a system.

给系统的静态与动态特征建模 unifies the best engineering practices for modeling

systems 集合了最好的工程实践方法 defines different graphical diagrams that provide multiple

perspectives of a system under development 多个视图 UML is a unification of the methodologies developed by

Grady Booch, James Rumbaugh, and Ivar Jacobsen. The Object Management Group (OMG), a not-for-profit

organization that Promotes the use of object-oriented technology, has responsibility for the further development of the UML

standard.


UMLUML

UML(Unified Modeling Language) 是下面这些最好的建模方法中最好部分的集成 :

◇ 业务流程模型 (Work Flow)

◇ 对象建模方法 ◇ 软构件建模思想

UML 是一种用可视化方法对软件系统进行描述、实施和说明的标准语言。

支持用不同实现技术进行的软件开发全过程。


UML DiagramsUML Diagrams

Use case diagram ( 用例图 ) Class diagram ( 类图 ) Object diagrams ( 对象图 ) Behavior diagrams:

Statechart diagram ( 状态图 ) Activity diagram ( 活动图 ) Interaction diagrams:

Sequence diagram ( 顺序图 ) Collaboration diagram ( 协作图 )

Implementation diagrams: Component diagram ( 组件图 ) Deployment diagram ( 部署图 )


UMLUML 的发展的发展


对对 UMLUML 做出贡献者做出贡献者


UMLUML 简介简介

Use CaseDiagramsUse Case

Diagrams用例图

ScenarioDiagramsScenario

Diagrams协作图State

DiagramsStateDiagrams构件图

ComponentDiagramsComponent

Diagrams部署图

StateDiagramsState

Diagrams对象图

ScenarioDiagramsScenario

Diagrams状态图

Use CaseDiagramsUse Case

Diagrams序列图

StateDiagramsState

Diagrams类图

活动图

UML


◇ 用例图用于显示若干角色以及这些角色与系统提供的功能之间的连接关系。

用例是系统提供的功能的描述


◇ 类图表示系统中的类和类与类之间的关系

它是对系统静态结构的描述


◇ 序列图

用来反映若干个对象之间的动态协作关系，也就是随着时间的推移，对象之间是如何交互的


◇ 协作图描述对象间的协作关系，协作图跟序列图相似，显示对象间的动态合作关系。

如果强调时间和顺序，则使用序列图；

如果强调上下级关系，则选择协作图。

这两种图合称为交互图。


◇ 状态图描述类的对象所有可能的状态以及事件发生时状态的转移条件。

通常，状态图是对类图的补充


◇ 活动图描述满足用例要求所要进行的活动以及活动间的约束关系，有利于识别并行活动


◇ 构件图描述代码构件的物理结构及各构件之间的依赖关系


◇ 部署图

部署图定义系统中软硬件的物理体系结构


Class Notation Class Notation 类的表示符号类的表示符号 A class

represented by a rectangle with three compartments. 分为三个部分的矩形框

The first compartment contains the name of the class 类名 ;

the second compartment describes the attributes of the class; 类的属性

third compartment describes the methods of the class.类的方法


Sample Sample

class Employee 类符号的多种形式 Representation Abbreviated representation Shortest form Essential representation


1.31.3.2 Relationships Between Classes .2 Relationships Between Classes

Associations 关联 One-way and Two-way Associations 单向与双向关

联 Multiplicity 多重性 Aggregation 聚合 Specialization/Generalization 具体化 / 抽象化


Associations Associations 关联关联 An association represents the relationship between

two or more classes. 类与其它类存在某种联系 A binary association is a relationship between two

classes. 二元关联An object of a class requires an object of another

class to do its work. 教师要求学生提交作业 In UML, a binary association is represented by a

solid line （实线） that connects the two classes. In a classroom, a professor instructs students.

In a bank system, clients hold bank accounts.


One-Way and Two-Way Associations One-Way and Two-Way Associations

An association can be a one-way or two-way relationship. A one-way association indicates 单向关联

the direction in which one can navigate from an object of one class to an object of another class. 学生看电影

A two-way association indicates 双向关联 bi-directional navigation between objects of two classes. 教学互动

difference one-way association : the first class has a reference( 引

用 ) to an object of the second class, but the second class does not have a reference to an object of the first class.

two-way association : each class contains a reference to an object of the other class.


UML samplesUML samples

UML indicates a one-way association with an arrow at the end of the association line.

The attribute in the first class that contains a reference to an object of the second class is also written at the end of the line.

One-way association between classes Car and Engine indicates that an engine is part of a car


samplessamples

the relationship between the classes Country, Government, and Capital the class Country has a reference to an object of

class Governmentthe class Country a reference to an object of

class Capital


A class can contain A class can contain more than one associationmore than one association with another class with another class

Two associations between classes Flight and Pilot, one association with the attribute pilot and another with the attribute coPilot.

如航班，飞行员与助驾


Multiplicity Multiplicity 多重性多重性 Multiplicity

indicates the number of instances of a class that may be associated with a single instance of another class. 对象关联时的数量特征

one car has four tires and one engine one client holds one or more bank accounts.

The multiplicity can be specified with a single integer a range n..m, where n is the lower limit and m is the upper limit. “ * “ used to denote no upper limit.

The following are the most common multiplicities: 0..1 Zero or one instance 0..* or * Zero or more instances 1 Exactly one instance 1..* One or more instances


One-to-one Association One-to-one Association

In a one-to-one association, exactly one instance of each class is related with exactly one instance of the other class.


One-to-many Association One-to-many Association

In a one-to-many association between classes A and B, one instance of class A may be related with

many instances of class B, but one instance of class B is related with exactly

one instance of class A.


Many-to-many Association Many-to-many Association

In a many-to-many association between classes A and B, one instance of class A may be related with

many instances of class Bone instance of class B may be related with

many instances of class A.


Aggregation Aggregation 聚合聚合 Aggregation 聚合

Each instance of class A is composed by instances of class B.

An instance of class B is part of an instance of class A.

The instance of class A is called the aggregate( 聚合体 )

The instance of class B is called the component( 部件 ).


Aggregation in UMLAggregation in UML


Specialization/Generalization Specialization/Generalization 具象化具象化 // 抽象化抽象化 (( 具体化具体化 // 一般化一般化 ))

Specialization/Generalization represents the is-a relationship. “ 是一个……”关系a whale is-a mammala client is-a person.

If specialization/generalization allows class A to be defined as specialization of another class B. Class A is called the specialization class 具体类

Whale, client

class B the generalization class. 一般类Mammal, person


Specialization/Generalization Specialization/Generalization

Specialization/generalization represented in UML by adding a triangle next to

the generalization class:


specialization/generalization relationshipspecialization/generalization relationship

If there is a specialization/generalization relationship between classes A and B ,so if A is-a B, then all instances of class A are also

instances of class B. java 程序设计 / 英语 / 大学物理教材书

An important consequence of this relationship is class A inherits all the features of class B. 继承All the attributes and methods of class B are also

attributes and methods of class A.


specialization/generalization relationshipspecialization/generalization relationship

The following class diagram represents the relationships Client is-a Person and Employee is-a Person:


Sample noteSample note

They are specialization/generalization relationshipsthe attributes of class Person are also attributes

of classes Client and Employee. Each instance of class Client contains the attributes

name, age, address , accounts (new attributes ); Each instance of class Employee contains the

attributes name, age, address, salary (new attributes ) , departments (new attributes )


Example of a system of multimedia files Example of a system of multimedia files

includes images, audio, and text files. The classes are defined as follows:


1.31.3.3 Common Class Structures.3 Common Class Structures

Introduction Collections Self-Containing Classes Relationship Loops


IntroductionIntroduction

Although the definition of classes and their relationships depends on the particular application, some class structures are common to many designs. 常用类结构

These class structures, which can be thought of as basic building blocks, can be composed to design complex systems. 像用各种预制件造高楼大厦


Collections Collections 集合集合 A collection models a

one-to-many relationship. Collections store many instances of one class. 同

一个类的多个实例班级 - 学生


samplesample

The diagram uses a collection to represent the relationship

"one client holds one or more bank accounts"defines methods to handle the collection of

BankAccount instances. Each BankAccount instance in the collection has an

index indicating its location in the collection.


Self-Containing Classes Self-Containing Classes 自包含自包含 A class can have an association with itself.

the class contains attributes with references to objects of the same class.


exampleexample

Class Person in a genealogical tree ( 家族谱系树 )system.

The relationships "each person has one mother" and "each person has one father" are indicated with the attributes mother and father.

The attributes mother and father are references to objects of class Person.


Another exampleAnother example

The relationship "each employee has one boss." The diagram indicates that the boss of an

employee is another employee.


Relationship Loops Relationship Loops 关系循环关系循环 Self-containment can be found in relationships that

include two or more classes. 循环自包含


exampleexample

A file system. A file system has folders, and folders contain files or

more folders, or both. We can define a class Folder, which contains a collection

of FolderItem objects:


1.31.3.4 UML with Eclipse .4 UML with Eclipse Introduction Create Project Create Folder Create New Class Diagram Create Class BankAccount Create Class Person Create Class Client Create Specialization/Generalization Relationship Create Association Relationship Export Image Note:

We can also use JUDE Download from :

http://jude.change-vision.com/jude-web/download/index.html


1.31.3.5 Modeling Classes.5 Modeling Classes

Process of Modeling Classes Identifying Classes Identifying Relationships Identifying Attributes Identifying Methods Modeling Using UML


Process of Modeling ClassesProcess of Modeling Classes

Object-oriented design is 面向对象设计the process of building an object model for a

system to be developed. OOD 就是一个建模过程 An object model specifies 对象模型详细指明了

the classes attributesMethodsrelationships with other classes.

How to building an object model from a system specification( 系统规格说明 ) ?


The steps to create an object modelThe steps to create an object model

1. Identify classes of objects from the system specification. 从规格说明中找出类

2. Identify relationships between classes. 找出类与类的关系

3. Identify attributes of each class. 找出每个类的属性

4. Identify methods of each class. 找出每个类的方法 5. Model system using UML. 用 UML 为系统建模


Identifying Classes Identifying Classes 找出类找出类 identify classes is to analyze the textual description

in the system specification. In textual analysis, the nouns and the noun phrases

often indicate objects and their classes. 名词 / 短语Singular nouns ( “book,” “library catalog,” and

“client“ ) and plural nouns ( ”users,” “books,” and “accounts” ) indicate classes. 单数与复数名词

Proper nouns ( “the ACME Bank” ) 专有名词nouns of direct reference ( “the person that

owned the account” ) indicate objects. 指代词


The steps for identifying the classes - 1The steps for identifying the classes - 11. List all nouns in the specification. 列出所有名词2. Prune the list: 对列表进行裁剪 ( 合并、简化 )

Convert plural nouns to their singular form. In an object model, class names are singular. 复数变单数

Eliminate nouns that represent objects. Replace them with generic nouns. 去掉特指变一般 use “client” instead of “John Smith.” “ 我去上 java 课”

Eliminate nouns that are class attributes. 去掉表示类属性的名词 If cannot identify the attributes of the noun, it is possible a class

attribute. 无法确定名词的属性，就可能是某类的属性3. Group the synonyms and then choose the best name for the

class from the group. 归纳同义词，起个恰当的名字 "user" and "client" are synonyms. In a bank system, the best name is "client" because the

system may have two types of users: the clients and the bank's employees.


The steps for identifying the classes - 2The steps for identifying the classes - 2

4. Select the classes that are relevant to the system. Look for more relevant classes. Search the application domain

for: 在应用领域进行搜索，找到与系统相关的类 Physical things. “person,” “book,” and “computer.” 现实事物 Roles played by persons or organizations.“employer” and

“supplier.” 角色 Objects that represents an occurrence or event. “system

crash,” “flight,” and “mouse click.” 表示发生的事件的对象 Objects that represent a relationship between other objects in

the model. “purchase” (related to “buyer,” “seller,” and “merchandise”) and “marriage” (related to “man” and “woman”). 表示关联关系的对象

People who carry out some function. "student" and "clerk." Places. “library,” “classroom,” and “bank.” 场所 Collections of objects, people, resources, or facilities. “catalog”

and “group.” 目标、人员、资源、设施集合 Concepts or ideas that are intangible. 抽象名词 “ money” and

“bank account.”


The steps for Identifying Relationships The steps for Identifying Relationships 找出关联找出关联 - 1- 1

1. Create an n x n table where n is the number of classes. Label the rows and columns with the

class names.


The steps for Identifying Relationships - 2The steps for Identifying Relationships - 2

2. identify the specialization/generalization relationships for each cell in the row A and column B, ask the

following questions: Is an instance of class A an instance of class B? Is an instance of class B an instance of class A?

Analyze the answer, If the answer both yes

the class names might be synonyms. the first is yes

class A is a specialization of class B. ( 子类关系 ) Mark the cell in the row A and column B with an

S. the second is yes, then

class A is a generalization of class B. ( 超类关系 ) Mark the cell in the row A and column B with a G.


The steps for Identifying Relationships - 3The steps for Identifying Relationships - 3

3. Identify the association relationships, evaluate each cell in the row A and column B: If no association between class A and class B 无关

mark the cell with an X. If one or more associations between class A and

class B, 存在某种关联性 insert the association attributes. “study," “buy,"

"ownedAccounts," and "clients."


The table told us …..The table told us …..

Shows the relationships "a client is a person that has one or more accounts." Indicates that Class Client is a specialization of class PersonClass Client has an association relationship with

class Account.


Identifying Attributes Identifying Attributes 找出属性找出属性 Look for adjectives and possessive phrases 所有格

"the X of Y" and "Y's X" in the system specification.

"number of the account" and "client's name.“

Use knowledge of the application domain to define the set of attributes needed for the system being developed. 问题领域的知识及经验，可从专业人员那里获取（因此设计开发前要详细调研）


Identifying Methods Identifying Methods 找出方法找出方法

To identify behaviors, look for verbs. "the client deposits money into the account“ indicates

that class Account should define a method deposit.

Use knowledge of the application domain to define the set of methods needed for the system being developed.


Identifying Methods Identifying Methods

除了以上的，还要利用开发者的经验一般的应用系统都有的方法 (或系统行为 )

Create and initialize new instances. 创建、初始化实例 Set and get values of attributes. 访问属性值 Load to and save from persistent storage. 持久存储访问 Destroy instances. 销毁实例 Perform calculations using an object‘s values. 执行计算 Output or display a result. 结果输出

If there are any collections held by the object, include the methods needed to add, remove, and

access elements of these collections. 集合操作


Modeling Using UML Modeling Using UML

Use class notation to represent classes Include attributes and methods. 类图

Use link notation to describe association and specialization/generalization relationships between classes. 关联

For associations, specify the multiplicity and the name of the attribute associated with the relationship. 多重性


1.31.3.6 Modeling the Library System .6 Modeling the Library System

Specification of the Library System Identifying Classes Identifying Relationships Identifying Attributes Identifying Methods Modeling Using UML


Specification of the Library System Specification of the Library System 规格说明规格说明 The library system tracks the items checked out by

borrowers. 管理图书借阅信息 The system contains a catalog of the items owned

by the library. There are two kinds of catalog items: books and recordings. All catalog items are identified by a unique code. (If the library owns several copies of the same book or recording, each copy has a unique code.) The information for each item includes title, year, and availability. An item is available if it is not checked out.


Specification of the Library SystemSpecification of the Library System

In addition: The information for a book includes the author and

number of pages. The information for a recording includes the

performer and format (CD or tape). The system contains a database of the borrowers.

Each borrower has a unique identification code in addition to a name. The system maintains a list, for each borrower, of the catalog items checked out.


Specification of the Library SystemSpecification of the Library System In the library system, the user should be able to:

Display the catalog by listing the code, title, and availability of each item.

Display a catalog item. Display the borrowers by listing the identification

code and name of each borrower. Display the catalog items checked out by a

borrower. Check out a catalog item by adding the item to

borrower's list of borrowed items. Check in a catalog item by removing the item

from borrower's list of borrowed items.


Identifying ClassesIdentifying Classes

First, we list the nouns in the system specification:

library system book CD

items recording tape

borrowers copy database

system information borrower

catalog item identification code

library title name

kinds year list

catalog items availability user

books author (borrower) code

audio items number of pages list of borrowed items

(item) code performer

copies format


Identifying ClassesIdentifying Classes Then, we prune the list by eliminating the following nouns:

(item) code, title, year, availability These nouns are attributes of a catalog item.

author, number of pages These nouns are attributes of a book.

performer, format These nouns are attributes of an audio item.

CD, tapeThese nouns are values for the attribute

format.

name, identification code, (borrower) code

These nouns are attributes of a borrower.

userThis noun is an element outside the library

system.

informationThis noun is a generic term for the class

attributes.

kinds This noun is not relevant to the system.


Identifying ClassesIdentifying Classes Next, we group the synonyms and then choose the best name

for the class from each group:

CatalogItem items, catalog items, copies, copy, item

LibrarySystem

library system, system, library

Borrower borrowers, borrower

Book books, book

Recording recordings, recording

BorrowedItems

list, list of borrowed items


Finally, we have ……Finally, we have ……

classes that are relevant to the system

LibrarySystem Catalog CatalogItem Book RecordingBorrower BorrowedItems BorrowerDatabase


Identifying Relationships Identifying Relationships

table identifies the association and specialization/generalization relationships:


Identifying AttributesIdentifying Attributes

The following is the list of attributes for each class:

Class Attributes

LibrarySystem catalog, borrowerDB

Catalog items

CatalogItem code, title, year, available

Book author, numberOfPages

Recording performer, format

Borrower name, id, borrowedItems

BorrowedItems items

BorrowerDatabase borrowers


Identifying MethodsIdentifying Methods

The following is the list of methods for each class:

Class Methods

LibrarySystem

displayCatalog() ， displayCatalogItem(),displayBorrowerDatabase(),displayBorrower(),checkIn(),checkOut()

Catalog addItem(item:CatalogItem)getItem(index:int):CatalogItem getNumberOfItems():Int getItem(code:String):CatalogItem

CatalogItem getCode():StringgetTitle():StringgetYear():intisAvailable():booleansetAvailable(value:boolean)




Class Methods

Book getAuthor():StringgetNumberOfPages():int

Recording getPerformer():StringgetFormat():String

Borrower getId():StringgetName():StringgetBorrowedItems():BorrowedItems




Class Methods

BorrowedItems addItem(item:CatalogItem)removeItem(item:CatalogItem)getItem(index:int):CatalogItemgetItem(code:String):CatalogItemgetNumberOfItems():int

BorrowerDatabase

addBorrower(borrower:Borrower)getBorrower(index:int):BorrowergetNumberOfBorrowers():intgetBorrower(id:String):Borrower


Modeling Using UMLModeling Using UML

The following is a class diagram for the library system:

object-oriented programme 1 ssd3: object-oriented programming and design

Documents

class design1

common class structures

twoway association

modeling classes

classes associations

development uml

binary association

uml standard