4.9 1 enumerations grocery items java

Simple JAVA Code

Define a utility class for displaying values of type double. Call the class DoubleOut. Include all the methods in the class DollarFormat, all the methods from the class OutputFormat , and a method called scienceWrite that displays a value of type double using e notation, such as 2 .13e-12. (This e notation is also called scientific notation, which explains the method name.) When displayed in e notation, the number should appear with exactly one nonzero digit before the decimal point-unless the number is exactly zero. The method scienceWrite will not advance to the next line. Also add a method called scienceWriteln that is the same as scienceWrite except that it does advance to the next line. All but the last two method definitions can simply be copied from the text (or more easily from the source code for this book that is available on the Web.). Note that you will be overloading the method names write and writeln.

Write a driver program to test your method scienceWriteln. This driver program should use a stub for the method scienceWri te. (Note that this means you can write and test scienceWriteln before you even write scienceWrite.) Then write a driver program to test the method sci enceWri te. Finally, write a program that is a sort of super driver program that takes a double value as input and then displays it using the two writeln methods and the scienceWriteln method. Use the number 5 for the number of digits after the decimal point when you need to specify such a number. This super driver program should allow the user to repeat this testing with additional numbers of type double until the user is ready to end the program.

Rubric

1. Completeness and Correctness of Code - 40 points

Chapter 1 Compiling a Java program, p. 20 Writing an algorithm, p. 25 Recognizing a hidden error, p. 28 Another applet example, p. 38 Writing an algorithm for Project 5, p. 42

Chapter 2 Another sample program, p. 61 Writing arithmetic expressions and statements, p. 72 Processing strings, p. 87 Pitfalls involving nextLine(), p. 97 Solving a conversion problem, p. 130 Solution to Project 13, p. 132

Chapter 3 Using multibranch if-else statements, p. 159 Using switch statements, p. 177 Solution to Project 2, p. 190 Responding to user input, p. 190

Chapter 4 Using nested while loops, p. 213 Comparing loop statements, p. 221 Debugging a loop, p. 238 Solution to Project 9, p. 252 Nesting for statements, p. 253

Chapter 5 Writing and involving methods, p. 292 Investigating public and private access, p. 300 Objects and references, p. 326 Exploring parameters of class types, p. 345 Developing a solution to Project 8, p. 363 Solution to Project 12, p. 366

Chapter 6 Writing construction, p. 387 Using static and non-static methods, p. 396 Writing and invoking overloaded methods, p. 433 Solving a similar problem, p. 468 Solution to Project 12, p. 469

(Continued on Inside Back Cover)

Through the power of practice and immediate personalized

feedback, MyProgrammingLab improves your performance.

Learn more at www.myprogramminglab.com

get with the programming

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An Introduction to Problem Solving & Programming

™

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Prentice Hall Boston Columbus Indianapolis New York San Francisco Upper Saddle River

Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montreal Toronto Delhi Mexico City São Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo

An Introduction to Problem Solving & Programming

Walter Savitch University of California, San Diego

Contributor

Kenrick Mock University of Alaska Anchorage

6th edition™

Credits and acknowledgments borrowed from other sources and reproduced, with permission, in this textbook appear on appropriate page within text.

Microsoft® and Windows® are registered trademarks of the Microsoft Corporation in the U.S.A. and other coun- tries. Screen shots and icons reprinted with permission from the Microsoft Corporation. This book is not spon- sored or endorsed by or affiliated with the Microsoft Corporation.

Copyright © 2012, 2009, 2005, 2004, 2001 Pearson Education, Inc., publishing as Prentice Hall, 1 Lake Street, Upper Saddle River, New Jersey, 07458. All rights reserved. Manufactured in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduc- tion, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopy- ing, recording, or likewise. To obtain permission(s) to use material from this work, please submit a written request to Pearson Education, Inc., Permissions Department, 1 Lake Street, Upper Saddle River, New Jersey, 07458

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viivii

Preface for Instructors

Welcome to the sixth edition of Java: An Introduction to Problem Solving & Programming. This book is designed for a first course in programming and computer science. It covers programming techniques, as well as the basics of the Java programming language. It is suitable for courses as short as one quar- ter or as long as a full academic year. No previous programming experience is required, nor is any mathematics, other than a little high school algebra. The book can also be used for a course designed to teach Java to students who have already had another programming course, in which case the first few chapters can be assigned as outside reading.

Changes in This Edition

The following list highlights how this sixth edition differs from the fifth edition: ■ Updates have been made for Java version 7, including strings in switch

statements and the use of type inference in generic instance creation. ■ Additional case studies including unit testing, use of the Comparable inter-

face, processing comma-separated value files, and others. ■ Chapter 5 now begins with a simpler class to more gradually introduce how

classes are constructed. ■ Chapter 8 has been reorganized with a greater emphasis and more examples

on polymorphism and interfaces. ■ Chapter 2 describes how to create a Swing application using the JFrame

class so thereafter students have the option of implementing graphics in applets or in an application.

■ Chapter 12 includes an overview of the Java Collections Framework and examples using the HashMap and HashSet classes.

■ A description of System.out.printf has been added to Chapter 2. ■ A description of Math.random has been added to Chapter 6. ■ Twenty new programming projects have been added. ■ New VideoNotes added throughout the text to enhance student

understanding of programming concepts and techniques.

viii PREFACE FOR INSTRUCTORS

Latest Java Coverage

All of the code in this book has been tested using a pre-release version of Oracle’s Java SE Development Kit (JDK), version 7.0. Any imported classes are standard and in the Java Class Library that is part of Java. No additional classes or specialized libraries are needed.

Flexibility

If you are an instructor, this book adapts to the way you teach, rather than making you adapt to the book. It does not tightly prescribe the sequence in which your course must cover topics. You can easily change the order in which you teach many chapters and sections. The particulars involved in rearranging material are explained in the dependency chart that follows this preface and in more detail in the “Prerequisites” section at the start of each chapter.

Early Graphics

Graphics supplement sections end each of the first ten chapters. This gives you the option of covering graphics and GUI programming from the start of your course. The graphics supplement sections emphasize applets but also cover GUIs built using the JFrame class. Any time after Chapter 8, you can move on to the main chapters on GUI programming (Chapters 13 through 15), which are now on the Web. Alternatively, you can continue through Chapter 10 with a mix of graphics and more traditional programming. Instructors who prefer to postpone the coverage of graphics can postpone or skip the graphics supplement sections.

Coverage of Problem-Solving and Programming Techniques

This book is designed to teach students basic problem-solving and program- ming techniques and is not simply a book about Java syntax. It contains numerous case studies, programming examples, and programming tips. Ad- ditionally, many sections explain important problem-solving and program- ming techniques, such as loop design techniques, debugging techniques, style techniques, abstract data types, and basic object-oriented programming tech- niques, including UML, event-driven programming, and generic programming using type parameters.

Early Introduction to Classes

Any course that really teaches Java must teach classes early, since everything in Java involves classes. A Java program is a class. The data type for strings of characters is a class. Even the behavior of the equals operator (==) depends on whether it is comparing objects from classes or simpler data items. Classes cannot be avoided, except by means of absurdly long and complicated “magic formulas.” This book introduces classes fairly early. Some exposure to using classes is given in Chapters 1 and 2. Chapter 5 covers how to define classes. All

PREFACE FOR INSTRUCTORS ix

of the basic information about classes, including inheritance, is presented by the end of Chapter 8 (even if you omit Chapter 7). However, some topics regarding classes, including inheritance, can be postponed until later in the course.

Although this book introduces classes early, it does not neglect traditional programming techniques, such as top-down design and loop design tech- niques. These older topics may no longer be glamorous, but they are informa- tion that all beginning students need.

Generic Programming

Students are introduced to type parameters when they cover lists in Chapter 12. The class ArrayList is presented as an example of how to use a class that has a type parameter. Students are then shown how to define their own classes that include a type parameter.

Language Details and Sample Code

This book teaches programming technique, rather than simply the Java lan- guage. However, neither students nor instructors would be satisfied with an introductory programming course that did not also teach the programming language. Until you calm students’ fears about language details, it is often im- possible to focus their attention on bigger issues. For this reason, the book gives complete explanations of Java language features and lots of sample code. Programs are presented in their entirety, along with sample input and output. In many cases, in addition to the complete examples in the text, extra complete examples are available over the Internet.

Self-Test Questions

Self-test questions are spread throughout each chapter. These questions have a wide range of difficulty levels. Some require only a one-word answer, whereas others require the reader to write an entire, nontrivial program. Complete an- swers for all the self-test questions, including those requiring full programs, are given at the end of each chapter.

Exercises and Programming Projects

Completely new exercises appear at the end of each chapter. Since only you, and not your students, will have access to their answers, these exercises are suitable for homework. Some could be expanded into programming projects. However, each chapter also contains other programming projects, several of which are new to this edition.

Support Material

The following support materials are available on the Internet at www.pearsonhighered.com/irc:

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x PREFACE FOR INSTRUCTORS

For instructors only:

■ Solutions to most exercises and programming projects ■ PowerPoint slides ■ Lab Manual with associated code.

Instructors should click on the registration link and follow instructions to re- ceive a password. If you encounter any problems, please contact your local Pearson Sales Representative. For the name and number of your sales represen- tative, go to pearsonhighered.com/replocator.

For students: ■ Source code for programs in the book and for extra examples ■ Student lab manual ■ VideoNotes: video solutions to programming examples and exercises.

Visit www.pearsonhighered.com/savitch to access the student resources.

Online Practice and Assessment with MyProgrammingLab

MyProgrammingLab helps students fully grasp the logic, semantics, and syn- tax of programming. Through practice exercises and immediate, personalized feedback, MyProgrammingLab improves the programming competence of be- ginning students who often struggle with the basic concepts and paradigms of popular high-level programming languages.

A self-study and homework tool, a MyProgrammingLab course consists of hundreds of small practice problems organized around the structure of this textbook. For students, the system automatically detects errors in the logic and syntax of their code submissions and offers targeted hints that enable students to figure out what went wrong—and why. For instructors, a comprehensive gradebook tracks correct and incorrect answers and stores the code inputted by students for review.

MyProgrammingLab is offered to users of this book in partnership with Turing’s Craft, the makers of the CodeLab interactive programming exer- cise system. For a full demonstration, to see feedback from instructors and students, or to get started using MyProgrammingLab in your course, visit www.myprogramminglab.com.

VideoNotes

VideoNotes are Pearson’s new visual tool designed for teaching students key programming concepts and techniques. These short step-by-step videos demonstrate how to solve problems from design through coding. VideoNotes allow for self-placed instruction with easy navigation including the ability to select, play, rewind, fast-forward, and stop within each VideoNote exercise.

VideoNote

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www.myprogramminglab.com
PREFACE FOR INSTRUCTORS xi

Margin icons in your textbook let you know when a VideoNote video is available for a particular concept or homework problem.

Integrated Development Environment Resource Kits

Professors who adopt this text can order it for students with a kit containing seven popular Java IDEs (the most recent JDK from Oracle, Eclipse, NetBeans, jGRASP, DrJava, BlueJ, and TextPad). The kit also includes access to a website containing written and video tutorials for getting started in each IDE. For ordering information, please contact your campus Pearson Education repre- sentative or visit www.pearsonhighered.com.

Contact Us

Your comments, suggestions, questions, and corrections are always welcome. Please e-mail them to savitch.programming.java@gmail.com.

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Preface for Students

This book is designed to teach you the Java programming language and, even more importantly, to teach you basic programming techniques. It requires no previous programming experience and no mathematics other than some simple high school algebra. However, to get the full benefit of the book, you should have Java available on your computer, so that you can practice with the examples and techniques given. The latest version of Java is preferable, but a version as early as 5 will do.

If You Have Programmed Before

You need no previous programming experience to use this book. It was designed for beginners. If you happen to have had experience with some other programming language, do not assume that Java is the same as the programming language(s) you are accustomed to using. All languages are different, and the differences, even if small, are large enough to give you problems. Browse the first four chapters, reading at least the Recap portions. By the time you reach Chapter 5, it would be best to read the entire chapter.

If you have programmed before in either C or C++, the transition to Java can be both comfortable and troublesome. At first glance, Java may seem almost the same as C or C++. However, Java is very different from these lan- guages, and you need to be aware of the differences. Appendix 6 compares Java and C++ to help you see what the differences are.

Obtaining a Copy of Java

Appendix 1 provides links to sites for downloading Java compilers and pro- gramming environments. For beginners, we recommend Oracle’s Java JDK for your Java compiler and related software and TextPad as a simple editor envi- ronment for writing Java code. When downloading the Java JDK, be sure to obtain the latest version available.

Support Materials for Students ■ Source code for programs in the book and for extra examples ■ Student lab manual ■ VideoNotes: video solutions to programming examples and exercises.

Visit www.pearsonhighered.com/savitch to access the student resources.

xii

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PREFACE FOR STUDENTS xiii

Learning Aids

Each chapter contains several features to help you learn the material:

■ The opening overview includes a brief table of contents, chapter objectives and prerequisites, and a paragraph or two about what you will study.

■ Recaps concisely summarize major aspects of Java syntax and other impor- tant concepts.

■ FAQs, or “frequently asked questions,” answer questions that other students have asked.

■ Remembers highlight important ideas you should keep in mind. ■ Programming Tips suggest ways to improve your programming skills. ■ Gotchas identify potential mistakes you could make—and should avoid—

while programming. ■ Asides provide short commentaries on relevant issues. ■ Self-Test Questions test your knowledge throughout, with answers given

at the end of each chapter. One of the best ways to practice what you are learning is to do the self-test questions before you look at the answers.

■ A summary of important concepts appears at the end of each chapter.

Online Practice with MyProgrammingLab

A self-study and practice tool, a MyProgrammingLab course consists of hundreds of small practice problems organized around the structure of this textbook. The system automatically detects errors in the logic and syntax of your code submissions and offers targeted hints that enable you to figure out what went wrong—and why. Visit www.myprogramminglab.com for more information.

VideoNotes

These short step-by-step videos demonstrate how to solve problems from design through coding. VideoNotes allow for self-placed instruction with easy navigation including the ability to select, play, rewind, fast-forward, and stop within each VideoNote exercise. Margin icons in your textbook let you know when a VideoNote video is available for a particular concept or homework problem.

This Text Is Also a Reference Book

In addition to using this book as a textbook, you can and should use it as a reference. When you need to check a point that you have forgotten or that you hear mentioned by somebody but have not yet learned yourself, just look in the index. Many index entries give a page number for a “recap.” Turn to that page. It will contain a short, highlighted entry giving all the essential points

VideoNote

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xiv PREFACE FOR STUDENTS

on that topic. You can do this to check details of the Java language as well as details on programming techniques.

Recap sections in every chapter give you a quick summary of the main points in that chapter. Also, a summary of important concepts appears at the end of each chapter. You can use these features to review the chapter or to check details of the Java language.

Acknowledgments

We thank the many people who have made this sixth edition possible, in- cluding everyone who has contributed to the first five editions. We begin by recognizing and thanking the people involved in the development of this new edition. The comments and suggestions of the following reviewers were in- valuable and are greatly appreciated. In alphabetical order, they are:

Asa Ben-Hur—Colorado State University Joan Boone—University of North Carolina at Chapel Hill Dennis Brylow—Temple University Billie Goldstein—Temple University Helen H. Hu—Westminster College Tammy VanDeGrift—University of Portland

Many other reviewers took the time to read drafts of earlier editions of the book. Their advice continues to benefit this new edition. Thank you once again to:

Gerald Baumgartner—Louisiana State University Jim Buffenbarger—Idaho State University Robert P. Burton—Brigham Young University Mary Elaine Califf—Illinois State University Steve Cater—Kettering University Martin Chelten—Moorpark Community College Ashraful A. Chowdhury—Georgia Perimeter College Ping-Chu Chu—Fayetteville State University Michael Clancy—University of California, Berkeley Tom Cortina—State University of New York at Stony Brook Prasun Dewan—University of North Carolina Laird Dornan—Sun Microsystems, Inc. H. E. Dunsmore—Purdue University, Lafayette Adel Elmaghraby—University of Louisville Ed Gellenbeck—Central Washington University Adrian German—Indiana University Gobi Gopinath—Suffolk County Community College Le Gruenwald—University of Oklahoma Gopal Gupta—University of Texas, Dallas Ricci Heishman—North Virginia Community College Robert Herrmann—Sun Microsystems, Inc., Java Soft Chris Hoffmann—University of Massachusetts, Amherst

xv

xvi ACKNOWLEDGMENTS

Robert Holloway—University of Wisconsin, Madison Charles Hoot—Oklahoma City University Lily Hou—Carnegie Mellon University Richard A. Johnson—Missouri State University Rob Kelly—State University of New York at Stony Brook Michele Kleckner—Elon College Stan Kwasny—Washington University Anthony Larrain—Depaul University Mike Litman—Western Illinois University Y. Annie Liu—State University of New York at Stony Brook Michael Long—California State University Blayne Mayfield—Oklahoma State University Drew McDermott—Yale University Gerald H. Meyer—LaGuardia Community College John Motil—California State University, Northridge Michael Olan—Stockton State Richard Ord—University of California, San Diego James Roberts—Carnegie Mellon University Alan Saleski—Loyola University Chicago Dolly Samson—Hawaii Pacific University Nan C. Schaller—Rochester Institute of Technology Arijit Sengupta—Raj Sion College of Business, Wright State University Ryan Shoemaker—Sun Microsystems, Inc. Liuba Shrira—Brandeis University Ken Slonneger—University of Iowa Donald E. Smith—Rutgers University Peter Spoerri—Fairfield University Howard Straubing—Boston College Navabi Tadayon—Arizona State University Boyd Trolinger—Butte College Tom Van Drunen—Wheaton College Subramanian Vijayarangam—University of Massachusetts, Lowell Stephen F.Weiss—University of North Carolina, Chapel Hill Richard Whitehouse—Arizona State University Michael Young—University of Oregon

Last but not least, we thank the many students in classes at the University of California, San Diego (UCSD), who were kind enough to help correct pre- liminary versions of this text, as well as the instructors who class-tested these drafts. In particular, we extend a special thanks to Carole McNamee of Cali- fornia State University, Sacramento, and to Paul Kube of UCSD. These student comments and the detailed feedback and class testing of earlier editions of the book were a tremendous help in shaping the final book.

W. S. K. M.

Dependency Chart

This chart shows the prerequisites for the chapters in the book. If there is a line between two boxes, the material in the higher box should be covered before the material in the lower box. Minor varia- tions to this chart are discussed in the “Prerequisites” section at the start of each chapter. These variations usually provide more, rather than less, flexibility that what is shown on the chart.

* Note that some sections of these chapters can be covered sooner. Those sections are given in this chart. ** These chapters contain sections that can be covered sooner. See the chapter’s “Prerequisites” section for full details.

Chapter 1 Introduction

Chapter 2 Primitive Types, Strings

Chapter 3 Flow of Control: Branching

Chapter 4 Flow of Control: Loops

Section 7.1 Array Basics

Chapter 7* Arrays

Chapter 11** Recursion

Chapter 8** Inheritance

Chapter 13** Basic Swing

Chapter 14 Applets

Chapter 15 More Swing

Chapter 9* Exceptions

Section 9.1 Exception Basics

Section 10.1 Overview of Files

Section 10.2 Text Files

Section 10.3 Any Files

Section 10.4 Binary Files

Section 10.5 File I/O for Objects

Section 10.6 Files and Graphics

Chapter 12** Data Structures, Generics

Chapter 5 and 6 Classes and Methods

xviii

Recaps Summarize Java syntax and other important concepts.

Remembers Highlight important ideas that students should keep in mind.

Features of This Text RECAP Bytes and Memory Locations

A computer’s main memory is divided into numbered units called bytes. The number of a byte is called its address. Each byte can hold eight binary digits, or bits, each of which is either 0 or 1. To store a piece of data that is too large to fit into a single byte, the computer uses several adjacent bytes. These adjacent bytes are thought of as a single, larger memory location whose address is the address of the first of the adjacent bytes.

REMEMBER Syntactic Variables

When you see something in this book like Type, Variable_1, or Variable_2 used to describe Java syntax, these words do not literally appear in your Java code. They are syntactic variables, which are a kind of blank that you fill in with something from the category that they describe. For example, Type can be replaced by int, double, char, or any other type name. Variable_1 and Variable_2 can each be replaced by any variable name.

■ PROGRAMMING TIP Initialize Variables A variable that has been declared, but that has not yet been given a value by an assignment statement (or in some other way), is said to be uninitialized. If the variable is a variable of a class type, it literally has no value. If the variable has a primitive type, it likely has some default value. However, your program will be clearer if you explicitly give the variable a value, even if you are simply reassigning the default value. (The exact details on default values have been known to change and should not be counted on.)

One easy way to ensure that you do not have an uninitialized variable is to initialize it within the declaration. Simply combine the declaration and an assignment statement, as in the following examples:

int count = 0;

double taxRate = 0.075;

char grade = 'A';

int balance = 1000, newBalance;

Note that you can initialize some variables and not initialize others in a declaration. Sometimes the compiler may complain that you have failed to initialize a

variable. In most cases, that will indeed be true. Occasionally, though, the compiler is mistaken in giving this advice. However, the compiler will not compile your program until you convince it that the variable in question is initialized. To make the compiler happy, initialize the variable when you declare it, even if the variable will be given another value before it is used for anything. In such cases, you cannot argue with the compiler. ■

GOTCHA Hidden Errors

Just because your program compiles and runs without any errors and even produces reasonable-looking output does not mean that your program is correct. You should always run your program with some test data that gives predictable output. To do this, choose some data for which you can compute the correct results, either by using pencil and paper, by looking up the answer, or by some other means. Even this testing does not guarantee that your program is correct, but the more testing you do, the more confidence you can have in your program. ■

FAQ11 FAQ stands for “frequently asked question.” Why just 0s and 1s?

Computers use 0s and 1s because it is easy to make an electrical device that has only two stable states. However, when you are programming, you normally need not be concerned about the encoding of data as 0s and 1s. You can program as if the computer directly stored numbers, letters, or strings of characters in memory. There is nothing special about calling the states zero and one. We could just as well use any two names, such as A and B or true and false. The important thing is that the underlying physical device has two stable states, such as on and off or high voltage and low voltage. Calling these two states zero and one is simply a convention, but it’s one that is almost universally followed.

Programming Tips Give students helpful advice about programming in Java.

Gotchas Identify potential mistakes in programming that students might make and should avoid.

FAQs Provide students answers to frequently asked questions within the context of the chapter.

FEATURES OF THIS TEXT xix

VideoNotes Step-by-step video solutions to programming examples and homework exercises.

CASE STUDY Unit Testing So far we’ve tested our programs by running them, typing in some input, and visually checking the results to see if the output is what we expected. This is fine for small programs but is generally insufficient for large programs. In a large program there are usually so many combinations of interacting inputs that it would take too much time to manually verify the correct result for all inputs. Additionally, it is possible that code changes result in unintended side effects. For example, a fix for one error might introduce a different error. One way to attack this problem is to write unit tests. Unit testing is a methodology in which the programmer tests the correctness of individual units of code. A unit is often a method but it could be a class or other group of code.

The collection of unit tests becomes the test suite. Each test is generally automated so that human input is not required. Automation is important because it is desirable to have tests that run often and quickly. This makes it possible to run the tests repeatedly, perhaps once a day or every time code is changed, to make sure that everything is still working. The process of running tests repeatedly is called regression testing.

Let’s start with a simple test case for the Species class in Listing 5.19. Our first test might be to verify that the name, initial population, and growth rate is correctly set in the setSpecies method. We can accomplish this by creating

Writing arithmetic expressions and statements

VideoNote

Case Studies Take students from problem statement to algorithm development to Java code.

Listings Show students complete programs with sample output.

LISTING 1.2 Drawing a Happy Face

import javax.swing.JApplet;

import java.awt.Graphics;

public class HappyFace extends JApplet {

public void paint(Graphics canvas) {

canvas.drawOval(100, 50, 200, 200); canvas.fillOval(155, 100, 10, 20); canvas.fillOval(230, 100, 10, 20); canvas.drawArc(150, 160, 100, 50, 180, 180);

} } Applet Output

xx FEATURES OF THIS TEXT

Programming Examples Provide more examples of Java programs that solve specific problems.

PROGRAMMING EXAMPLE Nested Loops

The body of a loop can contain any sort of statements. In particular, you can have a loop statement within the body of a larger loop statement. For example, the program in Listing 4.4 uses a while loop to compute the average of a list of nonnegative scores. The program asks the user to enter all the scores followed by a negative sentinel value to mark the end of the data. This while loop is placed inside a do-while loop so that the user can repeat the entire process for another exam, and another, until the user wishes to end the program.

SELF-TEST QUESTIONS

28. Given the class Species as defined in Listing 5.19, why does the following program cause an error message?

public class SpeciesEqualsDemo {

public static void main(String[] args) { Species s1, s2; s1. setSpecies("Klingon ox", 10, 15); s2.setSpecies("Klingon ox", 10, 15);

if (s1 == s2) System.out.println("Match with ==.");

else System.out.println("Do Notmatchwith ==.") } }

29. After correcting the program in the previous question, what output does the program produce?

30. What is the biggest difference between a parameter of a primitive type and a parameter of a class type?

31. Given the class Species, as defined in Listing 5.19, and the class

Self-Test Questions Provide students with the opportunity to practice skills learned in the chapter. Answers at the end of each chapter give immediate feedback.

Asides Give short commentary on relevant topics.

ASIDE Use of the Terms Parameter and Argument

Our use of the terms parameter and argument is consistent with common usage. We use parameter to describe the definition of the data type and variable inside the header of a method and argument to describe items passed into a method when it is invoked. However, people often use these terms interchangeably. Some people use the term parameter both for what we call a formal parameter and for what we call an argument. Other people use the term argument both for what we call a formal parameter and for what we call an argument. When you see the term parameter or argument in other books, you must figure out its exact meaning from the context.

xxi

Brief Table of Contents

Chapter 1 Introduction to Computers and Java 1

Chapter 2 Basic Computation 47

Chapter 3 Flow of Control: Branching 137

Chapter 4 Flow of Control: Loops 195

Chapter 5 Defining Classes and Methods 261

Chapter 6 More About Objects and Methods 373

Chapter 7 Arrays 479

Chapter 8 Inheritance, Polymorphism and Inheritance 575

Chapter 9 Exception Handling 657

Chapter 10 Streams and File I/O 725

Chapter 11 Recursion 799

Chapter 12 Dynamic Data Structures and Generics 847

Appendices 1 Getting Java 917 2 Running Applets 918

xxii BRIEF TABLE OF CONTENTS

3 Protected and Package Modifiers 920 4 The DecimalFormat Class 921 5 javadoc 925 6 Differences between C++ and Java 928 7 Unicode Character Codes 932

Index 933

The following chapters and appendices, along with an index to their contents, are on the book’s website:

Chapter 13 Window Interfaces Using Swing

Chapter 14 Applets and HTML

Chapter 15 More Swing

Appendices 8 The Iterator Interface 9 Cloning

xxiii

Table of Contents

Chapter 1 Introduction to Computers and Java 1

1.1 COMPUTER BASICS 2

Hardware and Memory 3

Programs 6

Programming Languages, Compilers, and Interpreters 7

Java Bytecode 9

Class Loader 11

1.2 A SIP OF JAVA 12

History of the Java Language 12

Applications and Applets 13

A First Java Application Program 14

Writing, Compiling, and Running a Java Program 19

1.3 PROGRAMMING BASICS 21

Object-Oriented Programming 21

Algorithms 25

Testing and Debugging 27

Software Reuse 28

1.4 GRAPHICS SUPPLEMENT 30

A Sample Graphics Applet 30

Size and Position of Figures 32

Drawing Ovals and Circles 34

Drawing Arcs 35

Running an Applet 37

Chapter 2 Basic Computation 47

2.1 VARIABLES AND EXPRESSIONS 48

Variables 49

Data Types 51

xxiv TABLE OF CONTENTS

Java Identifiers 53

Assignment Statements 55

Simple Input 58

Simple Screen Output 60

Constants 60

Named Constants 62

Assignment Compatibilities 63

Type Casting 65

Arithmetic Operators 68

Parentheses and Precedence Rules 71

Specialized Assignment Operators 72

Case Study: Vending Machine Change 74

Increment and Decrement Operators 79

More About the Increment and Decrement Operators 80

2.2 THE CLASS String 81

String Constants and Variables 81

Concatenation of Strings 82

String Methods 83

String Processing 85

Escape Characters 88

The Unicode Character Set 89

2.3 KEYBOARD AND SCREEN I/O 91

Screen Output 91

Keyboard Input 94

Other Input Delimiters (Optional) 99

Formatted Output with printf (Optional) 101

2.4 DOCUMENTATION AND STYLE 103

Meaningful Variable Names 103

Comments 104

Indentation 107

Using Named Constants 107

2.5 GRAPHICS SUPPLEMENT 109

Style Rules Applied to a Graphics Applet 110

Creating a Java GUI Application with the JFrame Class 110

Introducing the Class JOptionPane 113

Reading Input as Other Numeric Types 123

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Programming Example: Change-Making Program

with Windowing I/O 124

Chapter 3 Flow of Control: Branching 137

3.1 THE if-else STATEMENT 138

The Basic if-else Statement 139

Boolean Expressions 145

Comparing Strings 150

Nested if-else Statements 155

Multibranch if-else Statements 157

Programming Example: Assigning Letter Grades 159

Case Study: Body Mass Index 162

The Conditional Operator (Optional) 165

The exit Method 165

3.2 THE TYPE boolean 166

Boolean Variables 167

Precedence Rules 168

Input and Output of Boolean Values 171

3.3 THE switch STATEMENT 173

Enumerations 179

3.4 GRAPHICS SUPPLEMENT 180

Specifying a Drawing Color 181

A Dialog Box for a Yes-or-No Question 184

Chapter 4 Flow of Control: Loops 195

4.1 JAVA LOOP STATEMENTS 196

The while Statement 197

The do-while Statement 200

Programming Example: Bug Infestation 205

Programming Example: Nested Loops 211

The for Statement 213

Declaring Variables within a for Statement 219

Using a Comma in a for Statement (Optional) 220

The for-each Statement 222

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4.2 PROGRAMMING WITH LOOPS 222

The Loop Body 223

Initializing Statements 224

Controlling the Number of Loop Iterations 225

Case Study: Using a Boolean Variable to End a Loop 227

Programming Example: Spending Spree 229

The break Statement and continue Statement in Loops

(Optional) 232

Loop Bugs 235

Tracing Variables 237

Assertion Checks 239

4.3 GRAPHICS SUPPLEMENT 241

Programming Example: A Multiface Applet 241

The drawstring Method 247

Chapter 5 Defining Classes and Methods 261

5.1 CLASS AND METHOD DEFINITIONS 263

Class Files and Separate Compilation 265

Programming Example: Implementing a Dog Class 265

Instance Variables 266

Methods 269

Defining void Methods 272

Defining Methods That Return a Value 273

Programming Example: First Try at Implementing a Species Class 278

The Keyword this 282

Local Variables 284

Blocks 286

Parameters of a Primitive Type 287

5.2 INFORMATION HIDING AND ENCAPSULATION 293

Information Hiding 294

Precondition and Postcondition Comments 294

The public and private Modifiers 296

Programming Example: A Demonstration of Why Instance

Variables Should Be Private 299

Programming Example: Another Implementation of a Class

of Rectangles 300

Accessor Methods and Mutator Methods 302

TABLE OF CONTENTS xxvii

Programming Example: A Purchase Class 306

Methods Calling Methods 310

Encapsulation 316

Automatic Documentation with javadoc 319

UML Class Diagrams 320

5.3 OBJECTS AND REFERENCES 321

Variables of a Class Type 322

Defining an equals Method for a Class 327

Programming Example: A Species Class 331

Boolean-Valued Methods 334

Case Study: Unit Testing 336

Parameters of a Class Type 338

Programming Example: Class-Type Parameters Versus

Primitive-Type Parameters 342

5.4 GRAPHICS SUPPLEMENT 346

The Graphics Class 346

Programming Example: Multiple Faces, but with a Helping

Method 348

The init Method 352

Adding Labels to an Applet 352

Chapter 6 More About Objects and Methods 373

6.1 CONSTRUCTORS 375

Defining Constructors 375

Calling Methods from Constructors 384

Calling a Constructor from Other Constructors (Optional) 387

6.2 STATIC VARIABLES AND STATIC METHODS 389

Static Variables 389

Static Methods 390

Dividing the Task of a main Method into Subtasks 397

Adding a main Method to a Class 398

The Math Class 400

Wrapper Classes 403

6.3 WRITING METHODS 409

Case Study: Formatting Output 409

Decomposition 415

xxviii TABLE OF CONTENTS

Addressing Compiler Concerns 416

Testing Methods 418

6.4 OVERLOADING 420

Overloading Basics 420

Overloading and Automatic Type Conversion 423

Overloading and the Return Type 426

Programming Example: A Class for Money 428

6.5 INFORMATION HIDING REVISITED 435

Privacy Leaks 435

6.6 ENUMERATION AS A CLASS 439

6.7 PACKAGES 441

Packages and Importing 441

Package Names and Directories 443

Name Clashes 446

6.8 GRAPHICS SUPPLEMENT 447

Adding Buttons 447

Event-Driven Programming 449

Programming Buttons 449

Programming Example: A Complete Applet with Buttons 453

Adding Icons 456

Changing Visibility 458

Programming Example: An Example of Changing Visibility 458

Chapter 7 Arrays 479

7.1 ARRAY BASICS 481

Creating and Accessing Arrays 482

Array Details 485

The Instance Variable length 488

More About Array Indices 491

Initializing Arrays 494

7.2 ARRAYS IN CLASSES AND METHODS 495

Case Study: Sales Report 495

Indexed Variables as Method Arguments 503

Entire Arrays as Arguments to a Method 505

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Arguments for the Method main 507

Array Assignment and Equality 508

Methods That Return Arrays 511

7.3 PROGRAMMING WITH ARRAYS AND CLASSES 515

Programming Example: A Specialized List Class 515

Partially Filled Arrays 523

7.4 SORTING AND SEARCHING ARRAYS 525

Selection Sort 525

Other Sorting Algorithms 529

Searching an Array 531

7.5 MULTIDIMENSIONAL ARRAYS 532

Multidimensional-Array Basics 533

Multidimensional-Array Parameters and Returned Values 536

Java’s Representation of Multidimensional Arrays 539

Ragged Arrays (Optional) 540

Programming Example: Employee Time Records 542

7.6 GRAPHICS SUPPLEMENT 548

Text Areas and Text Fields 548

Programming Example: A Question-and-Answer Applet 548

The Classes JTextArea and JTextField 551

Drawing Polygons 553

Chapter 8 Inheritance, Polymorphism and Interfaces 575

8.1 INHERITANCE BASICS 576

Derived Classes 578

Overriding Method Definitions 582

Overriding Versus Overloading 583

The final Modifier 583

Private Instance Variables and Private Methods of a Base Class 584

UML Inheritance Diagrams 586

8.2 PROGRAMMING WITH INHERITANCE 589

Constructors in Derived Classes 589

The this Method—Again 591

Calling an Overridden Method 591

xxx TABLE OF CONTENTS

Programming Example: A Derived Class of a Derived Class 592

Another Way to Define the equals Methods in Undergraduate 597

Type Compatibility 597

The Class Object 602

A Better equals Method 604

8.3 POLYMORPHISM 606

Dynamic Binding and Inheritance 606

Dynamic Binding with toString 609

8.4 INTERFACES AND ABSTRACT CLASSES 611

Class Interfaces 611

Java Interfaces 612

Implementing an Interface 613

An Interface as a Type 615

Extending an Interface 618

Case Study: Character Graphics 619

Case Study: The Comparable Interface 632

Abstract Classes 636

8.5 GRAPHICS SUPPLEMENT 638

The Class JApplet 639

The Class JFrame 639

Window Events and Window Listeners 642

The ActionListener Interface 644

What to Do Next 644

Chapter 9 Exception Handling 657

9.1 BASIC EXCEPTION HANDLING 658

Exceptions in Java 659

Predefined Exception Classes 669

9.2 DEFINING YOUR OWN EXCEPTION CLASSES 671

9.3 MORE ABOUT EXCEPTION CLASSES 681

Declaring Exceptions (Passing the Buck) 681

Kinds of Exceptions 684

Errors 686

Multiple Throws and Catches 687

The finally Block 693

TABLE OF CONTENTS xxxi

Rethrowing an Exception (Optional) 694

Case Study: A Line-Oriented Calculator 695

9.4 GRAPHICS SUPPLEMENT 707

Exceptions in GUIs 707

Programming Example: A JFrame GUI Using Exceptions 707

Chapter 10 Streams and File I/O 725

10.1 AN OVERVIEW OF STREAMS AND FILE I/O 727

The Concept of a Stream 727

Why Use Files for I/O? 728

Text Files and Binary Files 728

10.2 TEXT-FILE I/O 730

Creating a Text File 730

Appending to a Text File 736

Reading from a Text File 738

10.3 TECHNIQUES FOR ANY FILE 741

The Class File 741

Programming Example: Reading a File Name

from the Keyboard 741

Using Path Names 743

Methods of the Class File 744

Defining a Method to Open a Stream 746

Case Study: Processing a Comma-Separated Values File 748

10.4 BASIC BINARY-FILE I/O 751

Creating a Binary File 751

Writing Primitive Values to a Binary File 753

Writing Strings to a Binary File 756

Some Details About writeUTF 757

Reading from a Binary File 759

The Class EOFException 764

Programming Example: Processing a File of Binary Data 766

10.5 BINARY-FILE I/O WITH OBJECTS AND ARRAYS 771

Binary-File I/O with Objects of a Class 771

Some Details of Serialization 775

Array Objects in Binary Files 776

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10.6 GRAPHICS SUPPLEMENT 779

Programming Example: A JFrame GUI for Manipulating Files 779

Chapter 11 Recursion 799

11.1 THE BASICS OF RECURSION 800

Case Study: Digits to Words 803

How Recursion Works 808

Infinite Recursion 812

Recursive Methods Versus Iterative Methods 814

Recursive Methods That Return a Value 816

11.2 PROGRAMMING WITH RECURSION 820

Programming Example: Insisting That User Input Be Correct 820

Case Study: Binary Search 822

Programming Example: Merge Sort—A Recursive Sorting Method 830

Chapter 12 Dynamic Data Structures and Generics 847

12.1 ARRAY-BASED DATA STRUCTURES 849

The Class ArrayList 850

Creating an Instance of ArrayList 850

Using the Methods of ArrayList 852

Programming Example: A To-Do List 856

Parameterized Classes and Generic Data Types 859

12.2 THE JAVA COLLECTIONS FRAMEWORK 859

The Collection Interface 860

The Class HashSet 861

The Map Interface 862

The Class HashMap 862

12.3 LINKED DATA STRUCTURES 865

The Class LinkedList 865

Linked Lists 866

Implementing the Operations of a Linked List 869

A Privacy Leak 876

Inner Classes 877

Node Inner Classes 878

Iterators 878

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The Java Iterator Interface 890

Exception Handling with Linked Lists 890

Variations on a Linked List 892

Other Linked Data Structures 894

12.4 GENERICS 895

The Basics 895

Programming Example: A Generic Linked List 898

APPENDICES

1 Getting Java 917

2 Running Applets 918

3 Protected and Package Modifiers 920

4 The DecimalFormat Class 921

Other Pattern Symbols 922

5 Javadoc 925

Commenting Classes for Use within javadoc 925

Running javadoc 926

6 Differences Between C++ and Java 928

Primitive Types 928

Strings 928

Flow of Control 928

Testing for Equality 929

main Method (Function) and Other Methods 929

Files and Including Files 929

Class and Method (Function) Definitions 930

No Pointer Types in Java 930

Method (Function) Parameters 930

Arrays 930

Garbage Collection 931

Other Comparisons 931

7 Unicode Character Codes 932

INDEX 933

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Introduction to Computers and Java

1.1 COMPUTER BASICS 2 Hardware and Memory 3 Programs 6 Programming Languages, Compilers, and

Interpreters 7 Java Bytecode 9 Class Loader 11

1.2 A SIP OF JAVA 12 History of the Java Language 12 Applications and Applets 13 A First Java Application Program 14 Writing, Compiling, and Running a Java

Program 19

1.3 PROGRAMMING BASICS 21 Object-Oriented Programming 21 Algorithms 25 Testing and Debugging 27 Software Reuse 28

1.4 GRAPHICS SUPPLEMENT 30 A Sample Graphics Applet 30 Size and Position of Figures 32 Drawing Ovals and Circles 34 Drawing Arcs 35 Running an Applet 37

1

Chapter Summary 38 Answers to Self-Test Questions 42Programming Projects 41

INTRODUCTION

This chapter gives you a brief overview of computer hardware and software. Much of this introductory material applies to programming in any language, not just to programming in Java. Our discussion of software will include a description of a methodology for designing programs known as object-oriented programming. Section 1.2 introduces the Java language and explains a sample Java program.

Section 1.4 is the first of a number of graphics supplements that end each of the first ten chapters and provide an introduction to the graphics capabilities of the Java language. These graphics supplements are interdependent, and each one uses the Java topics presented in its chapter.

OBJECTIVES

After studying this chapter, you should be able to

oriented programming in particular

PREREQUISITES

This first chapter does not assume that you have had any previous programming experience, but it does assume that you have access to a computer. To get the full value from the chapter, and from the rest of this book, you should have a computer that has the Java language installed, so that you can try out what you are learning. Appendix 1 describes how to obtain and install a free copy of the Java language for your computer.

1.1 COMPUTER BASICS The Analytical Engine has no pretensions whatever to originate anything. It can do whatever we know how to order it to perform. It can follow analysis; but it has no power of anticipating any analytical relations or truths. Its prov- ince is to assist us in making available what we are already acquainted with.

—ADA AUGUSTA, COUNTESS OF LOVELACE (1815–1852)

2

It is by no means hopeless to expect to make a machine for really very diffi- cult mathematical problems. But you would have to proceed step-by-step. I think electricity would be the best thing to rely on.

(1839–1914)

Computer systems consist of hardware and software. The hardware is the physical machine. A set of instructions for the computer to carry out is called a program. All the different kinds of programs used to give instructions to the computer are collectively referred to as software. software, but to understand software, it helps to know a few basic things about computer hardware.

Hardware and Memory

Most computers available today have the same basic components, configured in basically the same way. They all have input devices, such as a keyboard and a mouse. They all have output devices, such as a display screen and a printer. They also have several other basic components, usually housed in some sort of cabinet, where they are not so obvious. These other components store data and perform the actual computing.

The CPU, or central processing unit, or simply the processor, is the device inside your computer that follows a program’s instructions. Currently, one of

carry out only very simple instructions, such as moving numbers or other data from one place in memory to another and performing some basic arithmetic operations like addition and subtraction. The power of a computer comes from its speed and the intricacies of its programs. The basic design of the hardware is conceptually simple.

A computer’s memory holds data for the computer to process, and it holds the result of the computer’s intermediate calculations. Memory exists in two basic forms, known as main memory and auxiliary memory. Main memory holds the current program and much of the data that the program is manipulating. You most need to be aware of the nature of the main memory when you are writing programs. The information stored in main memory typically is volatile, that is, it disappears when you shut down your computer.

auxiliary memory, or secondary memory, exists even when the computer’s power is off. All of the various kinds of disks—including

To make this more concrete, let’s look at an example. You might have

of RAM and a 200-gigabyte hard drive. RAM—short for random access memory—is the main memory, and the hard drive is the principal—but

So 1 gigabyte of RAM is approximately 1 billion bytes of memory, and a 200-gigabyte hard drive has approximately 200 billion bytes of memory. What exactly is a byte? Read on.

The computer’s main memory consists of a long list of numbered bytes. The number of a byte is called its address. A byte is the smallest addressable unit of memory. A piece of data, such as a number or a keyboard character,

1.1 Computer Basics 3

Hardware and software make up a computer system

The CPU, or central processing unit, or processor, performs the instructions in a program

Main memory is volatile; auxiliary memory is not

4 CHAPTER 1 / Introduction to Computers and Java

can be stored in one of these bytes. When the computer needs to recover the data later, it uses the address of the byte to find the data item.

A byte, by convention, contains eight digits, each of which is either 0 or 1. Actually, any two values will do, but the two values are typically written as 0 and 1. Each of these digits is called a binary digit or, more typically, a bit. A byte, then, contains eight bits of memory. Both main memory and auxiliary memory are measured in bytes.

is encoded as a series of 0s and 1s and placed in the computer’s memory. As it turns out, one byte is just large enough to store a single keyboard character. This is one of the reasons that a computer’s memory is divided into these eight-bit bytes instead of into pieces of some other size. However, storing

When the computer needs to store a piece of data that cannot fit into a single byte, it uses several adjacent bytes. These adjacent bytes are then considered to be a single, larger memory location, and the address of the first byte is used as the address of the entire memory location. Figure 1.1 shows how a typical computer’s main memory might be divided into memory locations. The addresses of these larger locations are not fixed by the hardware but depend on the program using the memory.

Main memory consists of addressable eight-bit bytes

Groups of adjacent bytes can serve as a single memory location

FIGURE 1.1 Main Memory

2-byte memory location at address 3021

3-byte memory location at address 3024

2-byte memory location at address 3027

1-byte memory location at address 3023

11110000

11001100

00110001

11100001

10000001

10111100

01111111

11001110

10101010

01100011

10100010

3021

3022

3025

3026

3030

3031

3029

3024

3023

3027

3028

Bytes

Byte addresses

1.1 Computer Basics 5

Recall that main memory holds the current program and much of its data. Auxiliary memory is used to hold data in a more or less permanent form. Auxiliary memory is also divided into bytes, but these bytes are grouped into much larger units known as files. A file can contain almost any sort of data, such as a program, an essay, a list of numbers, or a picture, each in an encoded form. For example, when you write a Java program, you will store the program in a file that will typically reside in some kind of disk storage. When you use the program, the contents of the program file are copied from auxiliary memory to main memory.

You name each file and can organize groups of files into directories, or folders. Folder and directory are two names for the same thing. Some computer systems use one name, and some use the other.

A file is a group of bytes stored in auxiliary memory

A directory, or folder, contains groups of files

FAQ1 Why just 0s and 1s?

Computers use 0s and 1s because it is easy to make an electrical device that has only two stable states. However, when you are programming, you normally need not be concerned about the encoding of data as 0s and 1s. You can program as if the computer directly stored numbers, letters, or strings of characters in memory. There is nothing special about calling the states zero and one. We could just as well use any two names, such as A and B or true and false. The important thing is that the underlying physical device has two stable states, such as on and off or high voltage and low voltage. Calling these two states zero and one is simply a convention, but it’s one that is almost universally followed.

1

RECAP Bytes and Memory Locations

A computer’s main memory is divided into numbered units called bytes. The number of a byte is called its address. Each byte can hold eight binary digits, or bits, each of which is either 0 or 1. To store a piece of data that is too large to fit into a single byte, the computer uses several adjacent bytes. These adjacent bytes are thought of as a single, larger memory location whose address is the address of the first of the adjacent bytes.

6 CHAPTER 1 / Introduction to Computers and Java

Programs

You probably have some idea of what a program is. You use programs all the time. For example, text editors and word processors are programs. As we mentioned earlier, a program is simply a set of instructions for a computer to follow. When you give the computer a program and some data and tell the computer to follow the instructions in the program, you are running, or executing, the program on the data.

Figure 1.2 shows two ways to view the running of a program. To see the first way, ignore the dashed lines and blue shading that form a box. What’s left

has two kinds of input. The program is one kind of input; it contains the instructions that the computer will follow. The other kind of input is the data

For example, if the program is a spelling-check program, the data would be the text that needs to be checked. As far as the computer is concerned, both the data and the program itself are input. The output is the result—or

the program checks the spelling of some text, the output might be a list of words that are misspelled.

This first view of running a program is what really happens, but it is not always the way we think about running a program. Another way is to think of

the program are considered to be one unit. Figure 1.2 illustrates this view by surrounding the combined program–computer unit with a dashed box and blue shading. When we take this view, we think of the data as input to the program and the results as output from the program. Although the computer is understood to be there, it is presumed just to be something that assists