Download Chapter 9: Object-Oriented Software Development

Chapter 1 Object-Oriented Design
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Objectives

To become familiar with the process of program development
(§12.2).

To understand the relationship types: association, aggregation,
composition, strong inheritance, and weak inheritance (§12.3).

To declare classes to represent the relationships among the classes
(§12.3).
Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. All
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Software Development Process
Requirement
Specification
System
Analysis
System
Design
Implementation
Testing
Deployment
Maintenance
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Requirement Specification
Requirement
Specification
System
Analysis
System
Design
•A formal process
•to understand the problem
•document in detail what the software
system needs to do.
•involves close interaction between users
and designers.
Implementation
Testing
Most of the examples in this book are simple,
and their requirements are clearly stated.
In the real world, however, problems are not
well defined.
You need to study a problem carefully to
identify its requirements.
Deployment
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Maintenance
4
System Analysis
Requirement
Specification
Seeks to analyze the business
process in terms of data flow, and
to identify the system’s input and
output.
System
Analysis
System
Design
Implementation
Part of the analysis entails
modeling the system’s behavior.
The model is intended to capture the
essential elements of the system and
to define services to the system.
Testing
Deployment
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Maintenance
5
System Design
The process of designing the
system’s components
Requirement
Specification
System
Analysis
System
Design
Implementation
Testing
This phase involves the use of many levels
of abstraction to decompose the problem into
manageable components, identify classes and
interfaces, and establish relationships among
the classes and interfaces.
Deployment
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Maintenance
6
Implementation
The process of translating the
system design into programs.
Separate programs are written for
each component and put to work
together.
Requirement
Specification
System
Analysis
System
Design
Implementation
This phase requires the use of a
programming language like Java.
The implementation involves
coding, testing, and debugging.
Testing
Deployment
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Maintenance
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Testing
Requirement
Specification
Ensures that the code meets the
requirements specification and
weeds out bugs.
System
Analysis
System
Design
Implementation
An independent team of software
engineers not involved in the design
and implementation of the project
usually conducts such testing.
Testing
Deployment
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Maintenance
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Deployment
Requirement
Specification
Deployment makes the project
available for use.
System
Analysis
System
Design
Implementation
For a Java applet, this means
installing it on a Web server; for a
Java application, installing it on the
client's computer.
Testing
Deployment
Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. All
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Maintenance
9
Maintenance
Requirement
Specification
Maintenance is concerned with
changing and improving the
product.
System
Analysis
System
Design
Implementation
Testing
A software product must continue to perform and
improve in a changing environment.
This requires periodic upgrades of the product to fix
newly discovered bugs and incorporate changes.
Deployment
Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. All
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Maintenance
10
Relationships among Classes
 Association
 Aggregation
 Composition
 Inheritance
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Association
Association represents a general binary relationship that describes
an activity between two classes.
Student
5..60
public class Student {
/** Data fields */
private Course[]
courseList;
Take
* Course
0..3
public class Course {
/** Data fields */
private Student[]
classList;
private Faculty faculty;
/** Constructors */
/** Methods */
/** Constructors */
/** Methods */
}
Teach
1
Teacher
Faculty
public class Faculty {
/** Data fields */
private Course[]
courseList;
/** Constructors */
/** Methods */
}
}
An association is usually represented as a data field in the class.
Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. All
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Translation is not Unique
NOTE: If you don’t need to know the courses a student
takes or a faculty teaches, the data field coureList in Student
or Faculty can be omitted.
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Association Between Same Class
Association may exist between objects of the same class.
For example, a person may have a supervisor.
1
Person
Supervisor
1
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Aggregation and Composition
Aggregation is a special form of association, which
represents an ownership relationship between two classes.
Aggregation models the has-a relationship.
If an object is exclusively owned by an aggregated object,
the relationship between the object and its aggregated
object is referred to as composition.
Composition
Name
Aggregation
Person
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Address
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Representing Aggregation in Classes
An aggregation relationship is usually represented as a data
field in the aggregated class.
public class Name {
/** Data fields */
/** Constructors */
/** Methods */
}
public class Person {
/** Data fields */
private Name name;
private Address address;
public class Address {
/** Data fields */
/** Constructors */
/** Methods */
}
/** Constructors */
/** Methods */
}
Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. All
rights reserved. 0-13-222158-6
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Dependency
 Relationship
between two classes where one
class (client) uses the other (supplier)
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Degree of Coupling
Coupling increases
Dependency, association, aggregation, composition
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Inner Classes Translation
If Name or Address is used in the Person class only, they can
be declared as an inner class in Person. For example,
public class Person {
private Name name;
private Address address;
...
class Name {
...
}
class Address {
...
}
}
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Inheritance
Inheritance models the is-an-extension-of
relationship between two classes.
public class Faculty extends Person {
Person
/** Data fields */
/** Constructors */
/** Methods */
Faculty
}
(A)
(B)
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Weak Inheritance Relationship
A weak is-an-extension-of relationship can be represented using
interfaces. For example, the weak is-an-extension-of relationship
“students are comparable based on their grades” can be represented
by implementing the Comparable interface, as follows:
public class Student extends Person
implements Comparable {
Person
/** Data fields, Constructors, and */
/** Methods */
Student
Comparable
/** Implement the compareTo method */
public int compareTo(Object object) {
// ...
}
}
(A)
(B)
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Class Design
1. Identify classes for the system (e.g, Person, Name, Address)
2. Establish relationships among classes (e.g, A borrower is a person
who has a loan)
3. Describe attributes and methods in each class (e.g, The Name class has
the properties firstName, lastName, their associated get and set
methods, and the getFullName method)
4. Implement the classes (coding the classes, often using get ans set
method)
Liang, Introduction to Java Programming, Sixth Edition, (c) 2007 Pearson Education, Inc. All
rights reserved. 0-13-222158-6
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Example 12.1 Borrowing Loans
Name
Person
-firstName: String
-mi: char
-lastName: String
-name: Name
-address: Address
+Person()
+Person(name: Name, address: Address)
+getName(): Name
+seName(name: Name): void
+getAddress(): Address
+setAddress(address: Address): void
+toString(): String
+Name()
+Name(firstName: String,
mi: char, lastName: String)
+getFirstName(): String
+getMi(): char
+getLastName(): String
+setFirstName(firstName:
String): void
+setMi(mi: char): void
+setLastName(lastName:
String): void
+getFullName(): String
Borrower
-loan: Loan
Loan
Defined in
Example 6.7
Name
Address
-street: String
-city: String
-state: String
-zip: String
+Address()
+Address(street: String, city: String,
state: String, zip: String)
+getStreet(): String
+getCity(): String
+getState(): String
+getZip(): String
+setStreet(street: String): void
+setCity(city: String): void
+setState(state: String): void
+setZip(zip: String): void
+getFullAddress(): String
+Borrower()
+Borrower(name: Name, address: Address)
+getLoan(): Loan
+setLoan(loan: Loan): void
+toString(): String
Loan
Person
Borrower Address
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Example 12.1 Borrowing Loans,
cont.
The following is a test program that uses the
classes Name, Person, Address,
Borrower, and Loan.
BorrowLoan
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Run
24
Example 12.2 The Rational Class
 Is
a subclass of Number class
 A rational number has a numerator (n) and
denominator (d) in the form n/d
 Cannot have a denominator of 0, but
numerator of 0 is fine.
 Rational numbers are used in exact
computations involving fractions
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Example 11.2 The Rational Class
1
java.lang.Number
+byteValue(): byte
+shortValue(): short
+intValue(): int
+longVlaue(): long
+floatValue(): float
+doubleValue():double
java.lang.Comparable
compareTo(Object): int
Rational
-numerator: long
-denominator: long
+Rational()
+Rational(numerator: long, denominator: long)
+getNumerator(): long
+getDenominator(): long
+add(secondRational: Rational): Rational
+multiply(secondRational: Rational): Rational
+subtract(secondRational: Rational): Rational
+divide(secondRational: Rational): Rational
+toString(): String
-gcd(n: long, d: long): long
1
Rational
TestRationalClass
Add, Subtract, Multiply, Divide
Run
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