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Chapter 10 Object-Oriented Modeling Prerequisites for Part II Chapter 5 Arrays Chapter 6 Objects and Classes Chapter 7 Strings You can cover GUI after Chapter 8 Chapter 8 Inheritance and Polymorphism Chapter 11 Getting Started with GUI Programming Chapter 9 Abstract Classes and Interfaces Chapter 12 Event-Driven Programming Chapter 10 Object-Oriented Modeling Chapter 15 Exceptions and Assertions You can cover Exceptions and I/O after Chapter 8 Chapter 16 Simple Input and Output Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 1 Objectives To become familiar with the process of program development (§10.2). To the relationship types: association, aggregation, strong inheritance, and weak inheritance (§10.3). To declare classes to represent the relationships among the classes (§10.3). To design systems by identifying the classes and discovering the relationships among these classes (§10.4). To implement the Rational class and process rational numbers using this class (§10.5). To design classes that follow the class-design guidelines (§10.6). To model dynamic behavior using sequence diagrams and statechart diagrams (§10.7 Optional) To know the concept of framework-based programming using Java API (§10.8). Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 2 Software Development Process Requirement Specification System Analysis System Design Implementation Testing Deployment Maintenance Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 3 Requirement Specification Requirement Specification System Analysis System Design A formal process that seeks to understand the problem and document in detail what the software system needs to do. This phase involves close interaction between users and designers. Implementation 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. Testing Deployment Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 Maintenance 4 System Analysis Requirement Specification System Analysis System Design Seeks to analyze the business process in terms of data flow, and to identify the system’s input and output. 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 Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 Maintenance 5 System Design Requirement Specification The process of designing the system’s components. System Analysis System Design Implementation 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. Testing Deployment Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 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 Maintenance Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 7 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 Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 Maintenance 8 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, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 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 Deployment environment. This requires periodic upgrades of the product to fix newly discovered bugs and incorporate changes. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 Maintenance 10 Relationships among Classes Association Aggregation Composition Inheritance Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 11 Association Association represents a general binary relationship that describes an activity between two classes. Student Take 5..60 * Course public class Student { /** Data fields */ private Course[] courseList; 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, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 12 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. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 13 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 Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 Address 14 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, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 15 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 { ... } } Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 16 Inheritance Inheritance models the is-a relationship between two classes. public class Student extends Person { Person /** Data fields */ /** Constructors */ /** Methods */ Faculty } (A) (B) Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 17 Weak Inheritance Relationship A weak is-a relationship can be represented using interfaces. For example, the weak is-a 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) Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 18 Class Design 1. Identify classes for the system. 2. Describe attributes and methods in each class. 3. Establish relationships among classes. 4. Create classes. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 19 Example 10.1 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 Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 20 Example 10.1 Borrowing Loans, cont. The following is a test program that uses the classes Name, Person, Address, Borrower, and Loan. BorrowLoan Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 Run 21 Example 10.2 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, denomination: 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 Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 22 Class Design Guidelines Designing a Single Class. Using Modifiers public, protected, private and static Using Inheritance or Composition Using Interfaces or Abstract Classes Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 23 Designing a Class A class should describe a single entity or a set of similar operations. A single entity with too many responsibilities can be broken into several classes to separate responsibilities. The String class, StringBuffer class, and StringTokenizer class all deal with strings, for example, but have different responsibilities. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 24 Designing a Class, cont. Classes are usually designed for use by many different customers. To make a class useful in a wide range of applications, the class should provide a variety of ways for customization through properties and methods. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 25 Designing a Class, cont. Classes are designed for reuse. Users can incorporate classes in many different combinations, orders, and environments. Therefore, you should design a class that imposes no restrictions on what or when the user can do with it, design the properties to ensure that the user can set properties in any order, with any combination of values, and design methods to function independently of their order of occurrence. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 26 Designing a Class, cont. Provide a public no-arg constructor and override the equals method and the toString method defined in the Object class whenever possible. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 27 Designing a Class, cont. Follow standard Java programming style and naming conventions. Choose informative names for classes, data fields, and methods. Always place the data declaration before the constructor, and place constructors before methods. Always provide a constructor and initialize variables to avoid programming errors. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 28 Using Visibility Modifiers class can present two contracts – one for the users of the class and one for the extenders of the class. Make the fields private and accessor methods public if they are intended for the users of the class. Make the fields or method protected if they are intended for extenders of the class. The contract for the extenders encompasses the contract for the users. The extended class may increase the visibility of an instance method from protected to public, or change its implementation, but you should never change the implementation in a way that violates that contract. 29 Each Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 Using Visibility Modifiers, cont. A class should use the private modifier to hide its data from direct access by clients. You can use get methods and set methods to provide users with access to the private data, but only to private data you want the user to see or to modify. A class should also hide methods not intended for client use. The gcd method in the Rational class in Example 10.2, “The Rational Class,” is private, for example, because it is only for internal use within the class. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 30 Using the static Modifier A property that is shared by all the instances of the class should be declared as a static property. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 31 Using Inheritance or Composition In general, the difference between inheritance and composition is the difference between the is-a relationship and the has-a relationship. For example, an apple is fruit; thus, you would use inheritance to model the relationship between the classes Apple and Fruit. A person has a name; thus, you would use composition to model the relationship between the classes Person and Name. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 32 Using Inheritance or Composition, cont. Sometimes, the choice between inheritance and composition is not obvious. For example, you have used inheritance to model the relationship between the classes Circle and Cylinder. One could argue that a cylinder consists of circles; thus, you might use composition to define the Cylinder class as follows: Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 33 Using Inheritance or Composition, cont. public class Cylinder { private Circle circle; /** Constructors */ /** Methods */ } Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 34 Using Inheritance or Composition, cont. Both designs are fine. Which one is preferred? If polymorphism is desirable, you need to use the inheritance design. If you don’t care about polymorphism, the composition design gives more flexibility because the classes are less dependent using composition than using inheritance. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 35 Using Interfaces or Abstract Classes Both interfaces and abstract classes can be used to generalize common features. How do you decide whether to use an interface or a class? In general, a strong is-a relationship that clearly describes a parent-child relationship should be modeled using classes. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 36 Using Interfaces or Abstract Classes, cont. For example, since an orange is a fruit, their relationship should be modeled using class inheritance. A weak is-a relationship, also known as an is-kind-of relationship, indicates that an object possesses a certain property. A weak is-a relationship can be modeled using interfaces. For example, all strings are comparable, so the String class implements the Comparable interface. A circle or a rectangle is a geometric object, for example, so Circle can be designed as a subclass of GeometricObject. Circles are different and comparable based on their radius, for example, so Circle can implement the Comparable 37 interface. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 Using Interfaces or Abstract Classes, cont. Interfaces are more flexible than abstract classes, because a subclass can extend only one superclass, but implement any number of interfaces. However, interfaces cannot contain concrete methods. You can combine the virtues of interfaces and abstract classes by creating an interface with a companion abstract class that implements the interface. So you can use the interface or its companion class whichever is more convenient. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 38 Sequence diagrams Sequence diagrams describe interactions among objects by depicting the time ordering of method invocations. Class role anObject: TheClass anotherObject: TheOtherClass Method Invocation aMethod() Activation anotherMethod() Method Invocation Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 39 Sequence diagrams, cont. : BorrowLoan name: Name address: Address loan: Loan borrower: Borrower setFirstName setMi setLastName setStreet setCity setState setZip setAnnualInterestRate setNumOfYears setLoanAmount setName setAddress setLoan Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 40 Statechart diagrams Statechart diagrams describe flow of control of the object. Indicate Initial State State1 Transition State2 Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 41 Statechart diagrams, cont. JVM loads the class for the object Use the new operator to create the object Class Loaded Invoke the finalize method on the object Object Created Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 Object Destroyed 42 Supplement P: Designing Generic Matrix Classes Objective: This example gives a generic class for matrix arithmetic. This class implements matrix addition and multiplication common for all types of matrices. GenericMatrix Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 43 Example 10.3, cont. GenericMatrix IntegerMatrix -matrix: Object[][] #GenericMatrix(matrix: Object[][]) +getMatrix(): Object[][] +setMatrix(matrix: Object[][]): void +addMatrix(secondMatrix: Object[][]): Object[][] +multiplyMatrix(secondMatrix: Object[][]): Object[][] +printResult(m1: GenericMatrix, m2: GenericMatrix, m3: GenericMatrix, op: char): void #createGenericMatrix():GenericMatrix #add(o1: Object, o2: Object): Object #multiply(o1: Object, o2: Object): Object #zero():Object Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 RationalMatrix 44 Example 10.3, cont. Objective: This example gives two programs that utilize the GenericMatrix class for integer matrix arithmetic and rational matrix arithmetic. IntegerMatrix TestIntegerMatrix Run RationalMatrix TestRationalMatrix Run Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 45 The Java API The Java API (Application Program Interface, Application Programming Interface, or Application Programmer interface) consists of numerous classes and interfaces grouped into more than a dozen of packages. You have used classes and interfaces in the java.lang, javax.swing, and java.util packages. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 46 Framework-Based Programming To create comprehensive projects, you have to use more classes and interfaces in the Java API. The classes and interfaces in the Java API establish a framework for programmers to develop applications using Java. For example, the classes and interfaces in the Java GUI API establish a framework for developing GUI programs. You have to use these classes and interfaces and follow their conventions and rules to create applications. This is referred to as framework-based programming. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 47 Framework-Based Programming, cont. Once you understand the concept of Java and object-orient programming, the most important lesson from now on is learning how to use the API to develop useful programs. The most effective way to achieve it is to imitate good examples. The book provides many carefully designed examples to demonstrate the concept of the framework-based programming using the Java API. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 48 Framework-Based Programming, cont. You will learn the Java GUI programming framework in Chapters 11, 12, 13, and 14, the Java exception handling framework in Chapter 15, the Java IO framework in Chapter 16, the Java collections framework in Chapter 18, the Java multithreading framework in Chapter 19, and JDBC in Chapter 25, Servlets in Chapter 26, Networking in Chapter 28, and RMI in Chapter 29. Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6 49