1. 1. Java Quick Reference Console InputGUI Input DialogScanner input = new Scanner(System.in); int intValue = input.nextInt(); long longValue = input.nextLong(); double doubleValue = input.nextDouble(); float floatValue = input.nextFloat(); String string = input.next();String string = JOptionPane.showInputDialog( "Enter input"); int intValue = Integer.parseInt(string); double doubleValue = Double.parseDouble(string); Message DialogConsole Output JOptionPane.showMessageDialog(null, "Enter input");System.out.println(anyValue);Primitive Data TypesArithmetic OperatorsAssignment Operatorsbyte short int long float double char boolean+ * / % ++var --var var++ var--= += -= *= /= %=8 bits 16 bits 32 bits 64 bits 32 bits 64 bits 16 bits true/falseaddition subtraction multiplication division remainder preincrement predecrement postincrement postdecrementassignment addition assignment subtraction assignment multiplication assignment division assignment remainder assignmentRelational OperatorsLogical Operatorsif Statements< >= == !=&& || ! ^if (condition) { statements; }less than less than or equal to greater than greater than or equal to equal to not equalshort circuit AND short circuit OR NOT exclusive ORswitch Statementsloop Statementsswitch (intExpression) { case value1: statements; break; ... case valuen: statements; break; default: statements; }while (condition) { statements; } do { statements; } while (condition); for (init; condition; adjustment) { statements; }if (condition) { statements; } else { statements; } if (condition1) { statements; } else if (condition2) { statements; } else { statements; }Companion Web site: www.pearsonhighered.com/liang
2. 2. Java Quick Reference Frequently Used Static Constants/Methods Math.PI Math.random() Math.pow(a, b) System.currentTimeMillis() System.out.println(anyValue) JOptionPane.showMessageDialog(null, message) JOptionPane.showInputDialog( prompt-message) Integer.parseInt(string) Double.parseDouble(string) Arrays.sort(type[] list) Arrays.binarySearch(type[] list, type key)Array/Length/Initializer int[] list = new int[10]; list.length; int[] list = {1, 2, 3, 4}; Multidimensional Array/Length/Initializer int[][] list = new int[10][10]; list.length; list[0].length; int[][] list = {{1, 2}, {3, 4}}; Ragged Array int[][] m = {{1, 2, 3, 4}, {1, 2, 3}, {1, 2}, {1}};Text File OutputFile ClassPrintWriter output = new PrintWriter(filename); output.print(...); output.println(...); output.printf(...);Object ClassFile file = new File(filename); file.exists() file.renameTo(File) file.delete()Object o = new Object(); o.toString(); o.equals(o1);Comparable InterfaceText File Inputc.compareTo(Comparable) c is a Comparable objectScanner input = new Scanner( new File(filename));String ClassArrayList ClassString s = "Welcome"; String s = new String(char[]); int length = s.length(); char ch = s.charAt(index); int d = s.compareTo(s1); boolean b = s.equals(s1); boolean b = s.startsWith(s1); boolean b = s.endsWith(s1); String s1 = s.trim(); String s1 = s.toUpperCase(); String s1 = s.toLowerCase(); int index = s.indexOf(ch); int index = s.lastIndexOf(ch); String s1 = s.substring(ch); String s1 = s.substring(i,j); char[] chs = s.toCharArray(); String s1 = s.replaceAll(regex,repl); String[] tokens = s.split(regex);ArrayList list = new ArrayList(); list.add(object); list.add(index, object); list.clear(); Object o = list.get(index); boolean b = list.isEmpty(); boolean b = list.contains(object); int i = list.size(); list.remove(index); list.set(index, object); int i = list.indexOf(object); int i = list.lastIndexOf(object);printf Method System.out.printf("%b %c %d %f %e %s", true, 'A', 45, 45.5, 45.5, "Welcome"); System.out.printf("%-5d %10.2f %10.2e %8s", 45, 45.5, 45.5, "Welcome");Companion Web site: www.pearsonhighered.com/liang
3. 3. INTRODUCTION TOJAVA TMPROGRAMMING COMPREHENSIVE VERSION Eighth EditionY. Daniel Liang Armstrong Atlantic State UniversityPrentice 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 Sao Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo
4. 4. Vice President and Editorial Director, ECS: Marcia J. Horton Editor in Chief, Computer Science: Michael Hirsch Executive Editor: Tracy Dunkelberger Assistant Editor: Melinda Haggerty Editorial Assistant: Allison Michael Vice President, Production: Vince OBrien Senior Managing Editor: Scott Disanno Production Editor: Irwin Zucker Senior Operations Specialist: Alan Fischer Marketing Manager: Erin Davis Marketing Assistant: Mack Patterson Art Director: Kenny Beck Cover Image: Male Ruby-throated Hummingbird / Steve Byland / Shutterstock; Hummingbird, Nazca Lines / Gary Yim / Shutterstock Art Editor: Greg Dulles Media Editor: Daniel SandinCopyright 2011, 2009, 2007, 2004 by Pearson Higher Education. Upper Saddle River, New Jersey, 07458. All right 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 reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. To obtain permission(s) to use materials from this work, please submit a written request to Pearson Higher Education, Permissions Department, 1 Lake Street, Upper Saddle River, NJ 07458. The author and publisher of this book have used their best efforts in preparing this book. These efforts include the development, research, and testing of the theories and programs to determine their effectiveness. The author and publisher make no warranty of any kind, expressed or implied, with regard to these programs or the documentation contained in this book. The author and publisher shall not be liable in any event for incidental or consequential damages in connection with, or arising out of, the furnishing, performance, or use of these programs.Library of Congress Cataloging-in-Publication Data on file.10 9 8 7 6 5 4 3 2 1 ISBN-13: 978-0-13-213080-6 ISBN-10: 0-13-213080-7
5. 5. This book is dedicated to Dr. S. K. Dhall and Dr. S. Lakshmivarahan of the University of Oklahoma, who inspired me in teaching and research. Thank you for being my mentors and advisors.To Samantha, Michael, and Michelle
6. 6. PREFACE fundamentals-firstproblem-drivenThis book uses the fundamentals-first approach and teaches programming concepts and techniques in a problem-driven way. The fundamentals-first approach introduces basic programming concepts and techniques before objects and classes. My own experience, confirmed by the experiences of many colleagues, demonstrates that new programmers in order to succeed must learn basic logic and fundamental programming techniques such as loops and stepwise refinement. The fundamental concepts and techniques of loops, methods, and arrays are the foundation for programming. Building the foundation prepares students to learn object-oriented programming, GUI, database, and Web programming. Problem-driven means focused on problem solving rather than syntax. We make introductory programming interesting by using interesting problems. The central thread of early chapters is on problem solving. Appropriate syntax and library are introduced to support the writing of a program for solving the problems. To support the teaching of programming in a problemdriven way, the book provides a wide variety of problems at various levels of difficulty to motivate students. In order to appeal to students in all majors, the problems cover many application areas in math, science, business, financials, gaming, animation, and multimedia.Two Versions comprehensive versionbrief versionThis comprehensive version covers fundamentals of programming, object-oriented programming, GUI programming, algorithms and data structures, concurrency, networking, internationalization, advanced GUI, database, and Web programming. It is designed to prepare students to become proficient Java programmers. A brief version (Introduction to Java Programming, Brief Version, Eighth Edition) is available for a first course on programming, commonly known as CS1. The brief version contains the first 20 chapters of the comprehensive version.Whats New in This Edition? This edition substantially improves Introduction to Java Programming, Seventh Edition. The major improvements are as follows: This edition is completely revised in every detail to enhance clarity, presentation, content, examples, and exercises.In the examples and exercises, which are provided to motivate and stimulate student interest in programming, one-fifth of the problems are new.early console inputIn the previous edition, console input was covered at the end of Chapter 2. The new edition introduces console input early in Chapter 2 so that students can write interactive programs early.hand trace boxThe hand trace box is added for many programs to help novice students to read and trace programs.multidimensional arraysSingle-dimensional arrays and multidimensional arrays are covered in two chapters to give instructors the flexibility to cover multidimensional arrays later.Sudoku problem simplifiedThe case study for the Sudoku problem has been moved to the Companion Website. A more pedagogically effective simple version of the Sudoku problem is presented instead.The design of the API for Java GUI programming is an excellent example of how the object-oriented principle is applied. Students learn better with concrete and visual examples.complete revisionnew problemsiv
7. 7. Preface v So, basic GUI now precedes the introduction of abstract classes and interfaces. The instructor, however, can still choose to cover abstract classes and interfaces before GUI.basic GUI earlierException handling is covered before abstract classes and interfaces so that students can build robust programs early. The instructor can still choose to cover exception handling later.exception handling earlierChapter 12, Object-Oriented Design and Patterns, in the previous edition has been replaced by spreading the design guidelines and patterns into several chapters so that these topics can be covered in appropriate context.design guidelinesThe chapter on sorting now follows right after the chapter on algorithm efficiency, so that students can immediately apply algorithm efficiency to sorting algorithms.sortingA brand-new bonus Chapter 44 covers Java 2D.Java 2DThe coverage on data structures is expanded with new bonus chapters on AVL trees, splay trees, 2-4 trees, B-trees, and red-black trees, and hashing. So the book can be used for a full data structures course.new data structures chaptersLearning Strategies A programming course is quite different from other courses. In a programming course, you learn from examples, from practice, and from mistakes. You need to devote a lot of time to writing programs, testing them, and fixing errors. For first-time programmers, learning Java is like learning any high-level programming language. The fundamental point is to develop the critical skills of formulating programmatic solutions for real problems and translating them into programs using selection statements, loops, methods, and arrays. Once you acquire the basic skills of writing programs using loops, methods, and arrays, you can begin to learn how to develop large programs and GUI programs using the objectoriented approach. When you know how to program and you understand the concept of object-oriented programming, learning Java becomes a matter of learning the Java API. The Java API establishes a framework for programmers to develop applications using Java. You have to use the classes and interfaces in the API and follow their conventions and rules to create applications. The best way to learn the Java API is to imitate examples and do exercises.Pedagogical Features The book uses the following elements to get the most from the material: Objectives list what students should have learned from the chapter. This will help them determine whether they have met the objectives after completing the chapter.Introduction opens the discussion with representative problems to give the reader an overview of what to expect from the chapter.Problems carefully chosen and presented in an easy-to-follow style, teach problem solving and programming concepts. The book uses many small, simple, and stimulating examples to demonstrate important ideas.Chapter Summary reviews the important subjects that students should understand and remember. It helps them reinforce the key concepts they have learned in the chapter.Review Questions are grouped by sections to help students track their progress and evaluate their learning.Programming Exercises are grouped by sections to provide students with opportunities to apply on their own the new skills they have learned. The level of difficulty is rated as easy (nolearn from mistakesprogrammatic solutionobject-oriented programmingJava API
8. 8. vi Preface asterisk), moderate (*), hard (**), or challenging (***). The trick of learning programming is practice, practice, and practice. To that end, the book provides a great many exercises. LiveLab is a course assessment and management system. Students can submit programs online. The system automatically grades the programs/multiple-choice quizzes and gives students instant feedback. Instructors can create custom programming exercises and quizzes as well as use the system prebuilt exercises and quizzes.Notes, Tips, and Cautions are inserted throughout the text to offer valuable advice and insight on important aspects of program development.Note Provides additional information on the subject and reinforces important concepts.Tip Teaches good programming style and practice.Caution Helps students steer away from the pitfalls of programming errors.Design Guide Provides the guidelines for designing programs.Flexible Chapter Orderings The book is designed to provide flexible chapter orderings to enable GUI, exception handling, recursion, generics, and the Java Collections Framework to be covered earlier or later. The diagram on the next page shows the chapter dependencies.Organization of the Book The chapters can be grouped into five parts that, taken together, form a comprehensive introduction to Java programming, data structures and algorithms, and database and Web programming. Because knowledge is cumulative, the early chapters provide the conceptual basis for understanding programming and guide students through simple examples and exercises; subsequent chapters progressively present Java programming in detail, culminating with the development of comprehensive Java applications. Part I: Fundamentals of Programming (Chapters 17) The first part of the book is a stepping stone, preparing you to embark on the journey of learning Java. You will begin to know Java (Chapter 1) and will learn fundamental programming techniques with primitive data types, variables, constants, assignments, expressions, and operators (Chapter 2), control statements (Chapters 34), methods (Chapter 5), and arrays (Chapters 67). After Chapter 6, you may jump to Chapter 20 to learn how to write recursive methods for solving inherently recursive problems. Part II: Object-Oriented Programming (Chapters 811, 1314, 19) This part introduces object-oriented programming. Java is an object-oriented programming language that uses abstraction, encapsulation, inheritance, and polymorphism to provide great flexibility, modularity, and reusability in developing software. You will learn programming with objects and classes (Chapters 810), class inheritance (Chapter 11), polymorphism (Chapter 11), exception handling (Chapter 13), abstract classes (Chapter 14), and interfaces (Chapter 14). Processing strings will be introduced in Chapter 9 along with text I/O. Binary I/O is introduced in Chapter 19.
9. 9. Part I: Fundamentals of ProgrammingPart II: Object-Oriented ProgrammingPart III: GUI ProgrammingPart IV: Data Structures and AlgorithmsCh 18Part V: Advanced Java ProgrammingChapter 8 Objects and ClassesChapter 12 GUI BasicsCh 6Chapter 20 RecursionChapter 29 MultithreadingChapter 9 Strings and Text I/OChapter 15 GraphicsCh 14Chapter 21 GenericsChapter 30 NetworkingChapter 2 Elementary ProgrammingChapter 10 Thinking in ObjectsChapter 16 Event-Driven ProgrammingChapter 22 Java Collections FrameworkChapter 31 InternationalizationChapter 3 SelectionsChapter 11 Inheritance and PolymorphismChapter 17 Creating Graphical User InterfacesChapter 23 Algorithm EfficiencyChapter 1 Introduction to Computers, Programs, and JavaChapter 4 LoopsChapter 13 Exception HandlingChapter 5 Methods Chapter 6 Single-Dimensional ArraysChapter 14 Abstract Classes and InterfacesChapter 24 Sorting Chapter 18 Applets and Multimedia Chapter 32 JavaBeans and Bean Events Chapter 33 Containers, Layout Managers, and Borders Chapter 34 Menus, Toolbars, and Dialogs Chapter 35 MVC and Swing ModelsChapter 38 Advanced Java Database ProgrammingChapter 25 Lists, Stacks, and Queues, and Priority QueuesChapter 39 ServletsChapter 26 Binary Search TreesChapter 40 JavaServer PagesChapter 27 Graphs and ApplicationsChapter 41 JSF and Visual Web DevelopmentChapter 28 Weighted Graphs and ApplicationsChapter 42 Web ServicesChapter 19 Binary I/O Chapter 7 Multidimensional ArraysChapter 37 Java Database ProgrammingChapter 45 AVL and Splay TreesChapter 43 Remote Method InvocationChapter 36 JTable and JTree Note: Chapters 120 are in the brief version of this book Note: Chapters 3848 are bonus chapters available from the Companion WebsiteChapter 46 2-4 Trees and B-Trees Chapter 44 Java 2D Chapter 47 Red-Black Trees Chapter 48 HashingPreface vii
10. 10. viii Preface Part III: GUI Programming (Chapters 12, 1518, 3236, and 44) This part introduces elementary Java GUI programming in Chapters 12 and 1518 and advanced Java GUI programming in Chapters 3236 and 44. Major topics include GUI basics (Chapter 12), drawing shapes (Chapter 15), event-driven programming (Chapter 16), creating graphical user interfaces (Chapter 17), and writing applets (Chapter 18). You will learn the architecture of Java GUI programming and use the GUI components to develop applications and applets from these elementary GUI chapters. The advanced GUI chapters introduce Java GUI programming in more depth and breadth. You will delve into JavaBeans and learn how to develop custom events and source components in Chapter 32, review and explore new containers, layout managers, and borders in Chapter 33, learn how to create GUI with menus, popup menus, toolbars, dialogs, and internal frames in Chapter 34, develop components using the MVC approach and explore the advanced Swing components JSpinner, JList, JComboBox, JSpinner, and JTable, and JTree in Chapters 35 and 36. Bonus Chapter 44 introduces Java 2D. Part IV: Algorithms and Data Structures (Chapters 2028, 4548) This part introduces the main subjects in a typical data structures course. Chapter 20 introduces recursion to write methods for solving inherently recursive problems. Chapter 21 introduces generics to improve software reliability. Chapter 22 introduces the Java Collection Framework, which defines a set of useful API for data structures. Chapter 23 introduces measurement of algorithm efficiency in order to choose an appropriate algorithm for applications. Chapter 24 introduces classic sorting algorithms. You will learn how to implement several classic data structures lists, queues, priority queues, binary search trees, AVL trees, splay trees, 2-4 trees, B-trees, and red-black trees in Chapters 2526 and 4547. Chapters 27 and 28 introduce graph applications. Chapter 48 introduces hashing. Part V: Advanced Java Programming (Chapters 2931, 3743) This part of the book is devoted to advanced Java programming. Chapter 29 treats the use of multithreading to make programs more responsive and interactive. Chapter 30 introduces how to write programs that talk with each other from different hosts over the Internet. Chapter 31 covers the use of internationalization support to develop projects for international audiences. Chapter 37 introduces the use of Java to develop database projects, Chapter 38 introduces advanced Java database programming, and Chapters 39 and 40 introduce how to use Java servlets and JSP to generate dynamic contents from Web servers. Chapter 41 introduces rapid Web application development using JavaServer Faces. Chapter 42 introduces Web services. Chapter 43 introduces remote method invocation.Java Development Tools IDE tutorialsYou can use a text editor, such as the Windows Notepad or WordPad, to create Java programs and to compile and run the programs from the command window. You can also use a Java development tool, such as TextPad, NetBeans, or Eclipse. These tools support an integrated development environment (IDE) for rapidly developing Java programs. Editing, compiling, building, executing, and debugging programs are integrated in one graphical user interface. Using these tools effectively can greatly increase your programming productivity. TextPad is a primitive IDE tool. NetBeans and Eclipse are more sophisticated, but they are easy to use if you follow the tutorials. Tutorials on TextPad, NetBeans and Eclipse can be found in the supplements on the Companion Website.LiveLab This book is accompanied by an improved faster Web-based course assessment and management system. The system has three main components:
11. 11. Preface ix Automatic Grading System: It can automatically grade programs from the text or created by instructors.Quiz Creation/Submission/Grading System: It enables instructors to create/modify quizzes that students can take and be graded upon automatically.Tracking grades, attendance, etc: The system enables the students to track grades and instructors, to view the grades of all students, and to track attendance.The main features of the Automatic Grading System are as follows: Allows students to compile, run and submit exercises. (The system checks whether their program runs correctlystudents can continue to run and resubmit the program before the due date.)Allows instructors to review submissions; run programs with instructor test cases; correct them; and provide feedback to students.Allows instructors to create/modify custom exercises, create public and secret test cases, assign exercises, and set due dates for the whole class or for individuals.All the exercises in the text can be assigned to students. Additionally, LiveLab provides extra exercises that are not printed in the text.Allows instructors to sort and filter all exercises and check grades (by time frame, student, and/or exercise).Allows instructors to delete students from the system.Allows students and instructors to track grades on exercises.The main features of the Quiz System are as follows: Allows instructors to create/modify quizzes from test bank or a text file or to create complete new tests online.Allows instructors to assign the quizzes to students and set a due date and test time limit for the whole class or for individuals.Allows students and instructors to review submitted quizzes.Allows students and instructors to track grades on quizzes.Video Notes are Pearsons 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. Video Notes allows for self-paced instruction with easy navigation including the ability to select, play, rewind, fast-forward, and stop within each Video Note exercise. Video Note margin icons in your textbook let you know what a Video Notes video is available for a particular concept or homework problem. Video Notes are free with the purchase of a new textbook. To purchase access to Video Notes, please go to www.pearsonhighered.com/liang.Student Resource Materials The student resources can be accessed through the Publishers Web site (www.pearsonhighered.com/liang) and the Companion Web site (www.cs.armstrong.edu/liang/intro8e). The resources include: Answers to review questionsSolutions to even-numbered programming exercises
12. 12. x Preface Source code for book examplesInteractive self-test (organized by chapter sections)LiveLabResource linksErrataVideo NotesWeb ChaptersTo access the Video Notes and Web Chapters, students must log onto www.pearsonhighered.com/liang and use the access card located in the front of the book to register and access the material. If there is no access card in the front of this textbook, students can purchase access by visiting www.pearsonhighered.com/liang and selecting purchase access to premium content.Additional Supplements The text covers the essential subjects. The supplements extend the text to introduce additional topics that might be of interest to readers. The supplements listed in this table are available from the Companion Web site.Supplements on the Companion Web site Part I General Supplements A Glossary B Installing and Configuring JDK C Compiling and Running Java from the Command Window D Java Coding Style Guidelines E Creating Desktop Shortcuts for Java Applications on Windows F Using Packages to Organize the Classes in the Text Part II IDE Supplements A TextPad Tutorial B NetBeans Tutorial | One Page Startup Instruction C Learning Java Effectively with NetBeans D Eclipse Tutorial | One Page Startup Instruction E Learning Java Effectively with Eclipse Part III Java Supplements A Java Characteristics B Discussion on Operator and Operand Evaluations C The & and | Operators D Bitwise Operations E Statement Labels with break and continueF G H I J KEnumerated Types Packages Regular Expressions Formatted Strings The Methods in the Object Class Hiding Data Fields and Static Methods L Initialization Blocks M Extended Discussions on Overriding Methods N Design Patterns O Text I/O Prior to JDK 1.5 (Reader and Writer Classes) P Assertions Q Packaging and Deploying Java Projects R Java Web Start S GridBagLayout | OverlayLayout | SpringLayout T Networking Using Datagram Protocol U Creating Internal Frames V Pluggable Look and Feel W UML Graphical Notations X Testing Classes Using JUnit Y JNI Z The StringTokenizer Class Part IV Database Supplements A SQL Statements for Creating and Initializing Tables Used in the Book
13. 13. Preface xi B C D E F G H IMySQL Tutorial Oracle Tutorial Microsoft Access Tutorial Introduction to Database Systems Relational Database Concept Database Design SQL Basics Advanced SQLPart V Web Programming Supplements A HTML and XHTML Tutorial B CSS Tutorial C XML D Java and XML E Tomcat Tutorial F More Examples on JSF and Visual Web DevelopmentInstructor Resource Materials The instructor resources can be accessed through the Publishers Web site (www.pearsonhighered.com/liang) and the Companion Web site (www.cs.armstrong.edu/liang/intro8e). For username and password information to the Liang 8e site, please contact your Pearson Representative. The resources include: PowerPoint lecture slides with source code and run program capacityInstructor solutions manualComputerized test generatorSample exams using multiple choice and short answer questions, write and trace programs, and correcting programming errors.LiveLabErrataVideo NotesWeb ChaptersTo access the Video Notes and Web Chapters, instructors must log onto www.pearsonhighered.com/liang and register.Acknowledgments I would like to thank Armstrong Atlantic State University for enabling me to teach what I write and for supporting me in writing what I teach. Teaching is the source of inspiration for continuing to improve the book. I am grateful to the instructors and students who have offered comments, suggestions, bug reports, and praise. This book has been greatly enhanced thanks to outstanding reviews for this and previous editions. The reviewers are: Elizabeth Adams (James Madison University), Syed Ahmed (North Georgia College and State University), Omar Aldawud (Illinois Institute of Technology), Yang Ang (University of Wollongong, Australia), Kevin Bierre (Rochester Institute of Technology), David Champion (DeVry Institute), James Chegwidden (Tarrant County College), Anup Dargar (University of North Dakota), Charles Dierbach (Towson University), Frank Ducrest (University of Louisiana at Lafayette), Erica Eddy (University of Wisconsin at Parkside), Deena Engel (New York University), Henry A Etlinger (Rochester Institute of Technology), James Ten Eyck (Marist College), Olac Fuentes (University of Texas at El Paso), Harold Grossman (Clemson University), Barbara Guillot (Louisiana State University), Ron Hofman (Red River College, Canada), Stephen Hughes (Roanoke College), Vladan Jovanovic (Georgia Southern University), Edwin Kay (Lehigh University), Larry King (University of Texas at Dallas), Nana Kofi (Langara College, Canada), George Koutsogiannakis (Illinois
14. 14. xii Preface Institute of Technology), Roger Kraft (Purdue University at Calumet), Hong Lin (DeVry Institute), Dan Lipsa (Armstrong Atlantic State University), James Madison (Rensselaer Polytechnic Institute), Frank Malinowski (Darton College), Tim Margush (University of Akron), Debbie Masada (Sun Microsystems), Blayne Mayfield (Oklahoma State University), John McGrath (J.P. McGrath Consulting), Shyamal Mitra (University of Texas at Austin), Michel Mitri (James Madison University), Kenrick Mock (University of Alaska Anchorage), Jun Ni (University of Iowa), Benjamin Nystuen (University of Colorado at Colorado Springs), Maureen Opkins (CA State University, Long Beach), Gavin Osborne (University of Saskatchewan), Kevin Parker (Idaho State University), Dale Parson (Kutztown University), Mark Pendergast (Florida Gulf Coast University), Richard Povinelli (Marquette University), Roger Priebe (University of Texas at Austin), Mary Ann Pumphrey (De Anza Junior College), Pat Roth (Southern Polytechnic State University), Ronald F. Taylor (Wright State University), Carolyn Schauble (Colorado State University), David Scuse (University of Manitoba), Ashraf Shirani (San Jose State University), Daniel Spiegel (Kutztown University), Amr Sabry (Indiana University), Lixin Tao (Pace University), Russ Tront (Simon Fraser University), Deborah Trytten (University of Oklahoma), Kent Vidrine (George Washington University), and Bahram Zartoshty (California State University at Northridge). It is a great pleasure, honor, and privilege to work with Pearson. I would like to thank Tracy Dunkelberger and her colleagues Marcia Horton, Margaret Waples, Erin Davis, Michael Hirsh, Matt Goldstein, Jake Warde, Melinda Haggerty, Allison Michael, Scott Disanno, Irwin Zucker, and their colleagues for organizing, producing, and promoting this project, and Robert Lentz for copy editing. As always, I am indebted to my wife, Samantha, for her love, support, and encouragement. Y. Daniel Liang y.daniel.liang@gmail.com www.cs.armstrong.edu/liang www.pearsonhighered.com/liang
15. 15. BRIEF CONTENTS 1 Introduction to Computers, Programs, 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31and Java Elementary Programming Selections Loops Methods Single-Dimensional Arrays Multidimensional Arrays Objects and Classes Strings and Text I/O Thinking in Objects Inheritance and Polymorphism GUI Basics Exception Handling Abstract Classes and Interfaces Graphics Event-Driven Programming Creating Graphical User Interfaces Applets and Multimedia Binary I/O Recursion Generics Java Collections Framework Algorithm Efficiency Sorting Lists, Stacks, Queues, and Priority Queues Binary Search Trees Graphs and Applications Weighted Graphs and Applications Multithreading Networking Internationalization1 23 71 115 155 197 235 263 301 343 373 405 431 457 497 533 571 613 649 677 707 727 765 791 821 857 891 939 971 1017 105732 JavaBeans and Bean Events 33 Containers, Layout Managers,1091and Borders Menus, Toolbars, and Dialogs MVC and Swing Models JTable and JTree Java Database Programming1111 1149 1187 1225 127334 35 36 37Chapters are available from the companion Web site at www.pearsonhighered.com/liang: 38 39 40 41 42 43 44 45 46 47 48Advanced Java Database Programming Servlets JavaServer Pages JSF and Visual Web Development Web Services Remote Method Invocation Java 2D AVL Trees and Splay Trees 2-4 Trees and B-Trees Red-Black Trees Hashing381 391 401 411 421 431 441 451 461 471 481APPENDIXES A B C D E FJava Keywords The ASCII Character Set Operator Precedence Chart Java Modifiers Special Floating-Point Values Number SystemsINDEX1309 1312 1314 1316 1318 1319 1323xiii
16. 16. CONTENTS Chapter 1 Introduction to Computers, Programs, and Java 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9Introduction What Is a Computer? Programs Operating Systems Java, World Wide Web, and Beyond The Java Language Specification, API, JDK, and IDE A Simple Java Program Creating, Compiling, and Executing a Java Program (GUI) Displaying Text in a Message Dialog BoxChapter 2 Elementary Programming 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18Introduction Writing Simple Programs Reading Input from the Console Identifiers Variables Assignment Statements and Assignment Expressions Named Constants Numeric Data Types and Operations Problem: Displaying the Current Time Shorthand Operators Numeric Type Conversions Problem: Computing Loan Payments Character Data Type and Operations Problem: Counting Monetary Units The String Type Programming Style and Documentation Programming Errors (GUI) Getting Input from Input DialogsChapter 3 Selections 3.1 3.2 3.3 3.4 3.5 3.6 3.7xivIntroduction boolean Data Type Problem: A Simple Math Learning Tool if Statements Problem: Guessing Birthdays Two-Way if Statements Nested if Statements1 2 2 5 7 8 10 11 13 16 23 24 24 26 29 29 30 31 32 37 39 41 43 44 47 50 51 53 55 71 72 72 73 74 75 79 80
17. 17. Contents xv 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19Common Errors in Selection Statements Problem: An Improved Math Learning Tool Problem: Computing Body Mass Index Problem: Computing Taxes Logical Operators Problem: Determining Leap Year Problem: Lottery switch Statements Conditional Expressions Formatting Console Output Operator Precedence and Associativity (GUI) Confirmation Dialogs81 82 84 85 88 90 91 93 95 95 97 98Chapter 4 Loops1154.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10116 116 124 126 128 129 130 131 135 139Introduction The while Loop The do-while Loop The for Loop Which Loop to Use? Nested Loops Minimizing Numeric Errors Case Studies Keywords break and continue (GUI) Controlling a Loop with a Confirmation DialogChapter 5 Methods 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12Introduction Defining a Method Calling a Method void Method Example Passing Parameters by Values Modularizing Code Problem: Converting Decimals to Hexadecimals Overloading Methods The Scope of Variables The Math Class Case Study: Generating Random Characters Method Abstraction and Stepwise RefinementChapter 6 Single-Dimensional Arrays 6.1 6.2 6.3 6.4 6.5Introduction Array Basics Problem: Lotto Numbers Problem: Deck of Cards Copying Arrays155 156 156 158 160 162 165 167 168 171 172 175 176 197 198 198 204 206 208
18. 18. xvi Contents 6.6 6.7 6.8 6.9 6.10 6.11Passing Arrays to Methods Returning an Array from a Method Variable-Length Argument Lists Searching Arrays Sorting Arrays The Arrays ClassChapter 7 Multidimensional Arrays 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8Introduction Two-Dimensional Array Basics Processing Two-Dimensional Arrays Passing Two-Dimensional Arrays to Methods Problem: Grading a Multiple-Choice Test Problem: Finding a Closest Pair Problem: Sudoku Multidimensional ArraysChapter 8 Objects and Classes 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11Introduction Defining Classes for Objects Example: Defining Classes and Creating Objects Constructing Objects Using Constructors Accessing Objects via Reference Variables Using Classes from the Java Library Static Variables, Constants, and Methods Visibility Modifiers Data Field Encapsulation Passing Objects to Methods Array of ObjectsChapter 9 Strings and Text I/O 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8Introduction The String Class The Character Class The StringBuilder/StringBuffer Class Command-Line Arguments The File Class File Input and Output (GUI) File DialogsChapter 10 Thinking in Objects 10.1 10.2 10.3 10.4 10.5Introduction Immutable Objects and Classes The Scope of Variables The this Reference Class Abstraction and Encapsulation209 212 215 216 219 223 235 236 236 238 240 241 242 244 248 263 264 264 266 270 270 274 278 282 283 286 287 301 302 302 313 315 320 322 325 329 343 344 344 345 346 347
19. 19. Contents xvii 10.6 10.7 10.8 10.9 10.10 10.11Object-Oriented Thinking Object Composition Designing the Course Class Designing a Class for Stacks Designing the GuessDate Class Class Design GuidelinesChapter 11 Inheritance and Polymorphism 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 11.10 11.11 11.12 11.13 11.14Introduction Superclasses and Subclasses Using the super Keyword Overriding Methods Overriding vs. Overloading The Object Class and Its toString() Method Polymorphism Dynamic Binding Casting Objects and the instanceof Operator The Objects equals() Method The ArrayList Class A Custom Stack Class The protected Data and Methods Preventing Extending and OverridingChapter 12 GUI Basics 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 12.9 12.10Introduction Swing vs. AWT The Java GUI API Frames Layout Managers Using Panels as Subcontainers The Color Class The Font Class Common Features of Swing GUI Components Image IconsChapter 13 Exception Handling 13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8 13.9 13.10Introduction Exception-Handling Overview Exception-Handling Advantages Exception Types More on Exception Handling The finally Clause When to Use Exceptions Rethrowing Exceptions Chained Exceptions Creating Custom Exception Classes351 353 355 357 359 362 373 374 374 380 382 383 384 384 385 387 389 390 393 394 396 405 406 406 406 408 411 417 419 419 420 422 431 432 432 434 437 439 445 447 447 447 448
20. 20. xviii ContentsChapter 14 Abstract Classes and Interfaces 14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 14.9 14.10 14.11 14.12 14.13Introduction Abstract Classes Example: Calendar and GregorianCalendar Interfaces Example: The Comparable Interface Example: The ActionListener Interface Example: The Cloneable Interface Interfaces vs. Abstract Classes Processing Primitive Data Type Values as Objects Sorting an Array of Objects Automatic Conversion between Primitive Types and Wrapper Class Types The BigInteger and BigDecimal Classes Case Study: The Rational ClassChapter 15 Graphics 15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8 15.9 15.10 15.11 15.12Introduction Graphical Coordinate Systems The Graphics Class Drawing Strings, Lines, Rectangles, and Ovals Case Study: The FigurePanel Class Drawing Arcs Drawing Polygons and Polylines Centering a String Using the FontMetrics Class Case Study: The MessagePanel Class Case Study: The StillClock Class Displaying Images Case Study: The ImageViewer ClassChapter 16 Event-Driven Programming 16.1 16.2 16.3 16.4 16.5 16.6 16.7 16.8 16.9 16.10 16.11 16.12Introduction Event and Event Source Listeners, Registrations, and Handling Events Inner Classes Anonymous Class Listeners Alternative Ways of Defining Listener Classes Problem: Loan Calculator Window Events Listener Interface Adapters Mouse Events Key Events Animation Using the Timer ClassChapter 17 Creating Graphical User Interfaces 17.1 17.2 17.3Introduction Buttons Check Boxes457 458 458 462 465 467 469 471 473 476 479 481 481 482 497 498 498 499 501 502 506 507 510 512 516 520 522 533 534 534 535 541 542 544 547 549 551 552 555 557 571 572 572 578
21. 21. Contents xix 17.4 17.5 17.6 17.7 17.8 17.9 17.10 17.11 17.12Radio Buttons Labels Text Fields Text Areas Combo Boxes Lists Scroll Bars Sliders Creating Multiple WindowsChapter 18 Applets and Multimedia 18.1 18.2 18.3 18.4 18.5 18.6 18.7 18.8 18.9 18.10 18.11 18.12Introduction Developing Applets The HTML File and the Tag Applet Security Restrictions Enabling Applets to Run as Applications Applet Life-Cycle Methods Passing Strings to Applets Case Study: Bouncing Ball Case Study: TicTacToe Locating Resources Using the URL Class Playing Audio in Any Java Program Case Study: Multimedia AnimationsChapter 19 Binary I/O 19.1 19.2 19.3 19.4 19.5 19.6 19.7Introduction How is I/O Handled in Java? Text I/O vs. Binary I/O Binary I/O Classes Problem: Copying Files Object I/O Random-Access FilesChapter 20 Recursion 20.1 20.2 20.3 20.4 20.5 20.6 20.7 20.8 20.9 20.10 20.11Introduction Problem: Computing Factorials Problem: Computing Fibonacci Numbers Problem Solving Using Recursion Recursive Helper Methods Problem: Finding the Directory Size Problem: Towers of Hanoi Problem: Fractals Problem: Eight Queens Recursion vs. Iteration Tail Recursion581 583 584 586 590 593 596 599 602 613 614 614 615 618 618 620 620 624 628 632 633 634 649 650 650 650 652 660 662 666 677 678 678 681 683 684 687 688 692 695 697 697
22. 22. xx ContentsChapter 21 Generics 21.1 21.2 21.3 21.4 21.5 21.6 21.7 21.8Introduction Motivations and Benefits Defining Generic Classes and Interfaces Generic Methods Raw Type and Backward Compatibility Wildcard Generic Types Erasure and Restrictions on Generics Case Study: Generic Matrix ClassChapter 22 Java Collections Framework 22.1 22.2 22.3 22.4 22.5 22.6 22.7 22.8 22.9 22.10 22.11 22.12Introduction Collections The Collection Interface and the AbstractCollection Class Sets The Comparator Interface Lists Static Methods for Lists and Collections Performance of Sets and Lists The Vector and Stack Classes Queues and Priority Queues Maps Singleton and Unmodifiable Collections and MapsChapter 23 Algorithm Efficiency 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9Introduction Big O Notation Examples: Determining Big O Analyzing Algorithm Time Complexity Case Studies: Finding Fibonacci Numbers Case Studies: Finding Greatest Common Divisors Case Studies: Finding Prime Numbers Case Studies: Closest Pair of Points Preview of Other AlgorithmsChapter 24 Sorting 24.1 24.2 24.3 24.4 24.5 24.6 24.7Introduction Bubble Sort Merge Sort Quick Sort Heap Sort Bucket Sort and Radix Sort External SortChapter 25 Lists, Stacks, Queues, and Priority Queues 25.1 25.2Introduction Common Features for Lists707 708 708 710 712 713 714 716 719 727 728 728 729 730 737 738 742 745 746 748 751 756 765 766 766 767 769 771 774 778 783 785 791 792 792 794 797 801 807 809 821 822 822
23. 23. Contents xxi 25.3 25.4 25.5 25.6 25.7 25.8Array Lists Linked Lists Variations of Linked Lists Stacks and Queues Priority Queues Case Study: Evaluating ExpressionsChapter 26 Binary Search Trees 26.1 26.2 26.3 26.4 26.5 26.6Introduction Binary Search Trees Deleting Elements in a BST Tree Visualization Iterators Case Study: Data CompressionChapter 27 Graphs and Applications 27.1 27.2 27.3 27.4 27.5 27.6 27.7 27.8 27.9 27.10Introduction Basic Graph Terminologies Representing Graphs Modeling Graphs Graph Visualization Graph Traversals Depth-First Search (DFS) Breadth-First Search (BFS) Case Study: The Nine Tail Problem Case Study: The Knights Tour ProblemChapter 28 Weighted Graphs and Applications 28.1 28.2 28.3 28.4 28.5 28.6Introduction Representing Weighted Graphs The WeightedGraph Class Minimum Spanning Trees Finding Shortest Paths Case Study: The Weighted Nine Tail ProblemChapter 29 Multithreading 29.1 29.2 29.3 29.4 29.5 29.6 29.7 29.8Introduction Thread Concepts Creating Tasks and Threads The Thread Class Example: Flashing Text GUI Event Dispatch Thread Case Study: Clock with Audio Thread Pools825 830 842 843 846 847 857 858 858 870 876 879 881 891 892 893 894 898 909 911 912 916 919 923 939 940 940 942 949 955 962 971 972 972 972 975 978 979 980 983
24. 24. xxii Contents 29.9 29.10 29.11 29.12 29.13 29.14 29.15 29.16 29.17 29.18 29.19Thread Synchronization Synchronization Using Locks Cooperation among Threads Case Study: Producer/Consumer Blocking Queues Semaphores Avoiding Deadlocks Thread States Synchronized Collections SwingWorkerDisplaying Progress Using JProgressBar985 989 991 995 998 1000 1001 1002 1002 1004 1007Chapter 30 Networking 30.1 30.2 30.3 30.4 30.5 30.6 30.7 30.8 30.91017 1018 1018 1025 1026 1029 1031 1036 1039 1041Introduction Client/Server Computing The InetAddress Class Serving Multiple Clients Applet Clients Sending and Receiving Objects Retrieving Files from Web Servers JEditorPaneCase Studies: Distributed TicTacToe GamesChapter 31 Internationalization 31.1 31.2 31.3 31.4 31.5 31.6Introduction The Locale Class Displaying Date and Time Formatting Numbers Resource Bundles Character Encoding1057 1058 1058 1060 1071 1077 1084Chapter 32 JavaBeans and Bean Events 32.1 32.2 32.3 32.4 32.5 32.6Introduction JavaBeans Bean Properties Java Event Model Review Creating Custom Source Components Creating Custom Event Sets1091 1092 1092 1093 1094 1097 1101Chapter 33 Containers, Layout Managers, and Borders 33.1 33.2 33.3 33.4Introduction Swing Container Structures Layout Managers Creating Custom Layout Managers1111 1112 1112 1114 1123
25. 25. Contents xxiii 33.5 33.6 33.7 33.8JScrollPane JTabbedPane JSplitPaneSwing BordersChapter 34 Menus, Toolbars, and Dialogs 34.1 34.2 34.3 34.4 34.5 34.6 34.7 34.8 34.9Introduction Menus Popup Menus JToolBarProcessing Actions Using the Action Interface JOptionPane Dialogs Creating Custom Dialogs JColorChooser JFileChooserChapter 35 MVC and Swing Models 35.1 35.2 35.3 35.4 35.5 35.6 35.7 35.8 35.9 35.10Introduction MVC MVC Variations Swing Model-View-Controller Architecture JSpinnerSpinner Models and Editors JList and its ModelsList Models List Cell Renderer JComboBox and its ModelsChapter 36 JTable and JTree 36.1 36.2 36.3 36.4 36.5 36.6 36.7 36.8 36.9 36.10 36.11 36.12 36.13 36.14 36.15Introduction JTableTable Models and Table Column Models Auto Sort and Filtering Case Study: Modifying Rows and Columns Table Renderers and Editors Custom Table Renderers and Editors Table Model Events JTree TreeModel and DefaultTreeModel TreeNode, MutableTreeNode, and DefaultMutableTreeNode TreePath and TreeSelectionModel Case Study: Modifying Trees Tree Node Rendering and Editing Tree Events1128 1132 1133 1136 1149 1150 1150 1156 1158 1160 1164 1171 1174 1176 1187 1188 1188 1194 1195 1196 1198 1205 1209 1212 1216 1225 1226 1226 1231 1235 1237 1242 1245 1247 1250 1254 1256 1259 1262 1265 1267
26. 26. xxiv ContentsChapter 37 Java Database Programming 37.1 37.2 37.3 37.4 37.5 37.6 37.7Introduction Relational Database Systems SQL JDBC PreparedStatement CallableStatementRetrieving Metadata1273 1274 1274 1278 1286 1295 1297 1300A detailed table of contents for the Web chapters is available on the companion Web site:Chapter 38 Advanced Java Database Programming381Chapter 39 Servlets391Chapter 40 JavaServer Pages401Chapter 41 JSF and Visual Web Development411Chapter 42 Web Services421Chapter 43 Remote Method Invocation431Chapter 44 Java 2D44-1Chapter 45 AVL Trees and Splay Trees45-1Chapter 46 2-4 Trees and B-Trees46-1Chapter 47 Red-Black Trees47-1Chapter 48 Hashing48-1APPENDIXES Appendix A Appendix B Appendix C Appendix D Appendix E Appendix FINDEXJava Keywords The ASCII Character Set Operator Precedence Chart Java Modifiers Special Floating-Point Values Number Systems1309 1312 1314 1316 1318 1319 1323
27. 27. CHAPTER 1 INTRODUCTION TO COMPUTERS, PROGRAMS, AND JAVA Objectives To review computer basics, programs, and operating systems (1.21.4).To explore the relationship between Java and the World Wide Web (1.5).To distinguish the terms API, IDE, and JDK (1.6).To write a simple Java program (1.7).To display output on the console (1.7).To explain the basic syntax of a Java program (1.7).To create, compile, and run Java programs (1.8).(GUI) To display output using the JOptionPane output dialog boxes (1.9).
28. 28. 2 Chapter 1 Introduction to Computers, Programs, and Java1.1 Introduction why Java?You use word processors to write documents, Web browsers to explore the Internet, and email programs to send email. These are all examples of software that runs on computers. Software is developed using programming languages. There are many programming languagesso why Java? The answer is that Java enables users to develop and deploy applications on the Internet for servers, desktop computers, and small hand-held devices. The future of computing is being profoundly influenced by the Internet, and Java promises to remain a big part of that future. Java is the Internet programming language. You are about to begin an exciting journey, learning a powerful programming language. At the outset, it is helpful to review computer basics, programs, and operating systems and to become familiar with number systems. If you are already familiar with such terms as CPU, memory, disks, operating systems, and programming languages, you may skip the review in 1.21.4.1.2 What Is a Computer? hardware softwareA computer is an electronic device that stores and processes data. It includes both hardware and software. In general, hardware comprises the visible, physical elements of the computer, and software provides the invisible instructions that control the hardware and make it perform specific tasks. Writing instructions for computers to perform is called computer programming. Knowing computer hardware isnt essential to your learning a programming language, but it does help you understand better the effect of the program instructions. This section introduces computer hardware components and their functions. A computer consists of the following major hardware components (Figure 1.1): Central processing unit (CPU)Memory (main memory)Storage devices (e.g., disks, CDs, tapes)Input and output devices (e.g., monitors, keyboards, mice, printers)Communication devices (e.g., modems and network interface cards (NICs)) BusStorage DevicesMemoryCPUe.g., Disk, CD, and TapeCommunication DevicesInput DevicesOutput Devicese.g., Modem and NICe.g., Keyboard, Mousee.g., Monitor, PrinterFIGURE 1.1 A computer consists of CPU, memory, storage devices, input devices, output devices, and communication devices. busThe components are connected through a subsystem called a bus that transfers data or power between them.1.2.1 Central Processing Unit CPUThe central processing unit (CPU) is the computers brain. It retrieves instructions from memory and executes them. The CPU usually has two components: a control unit and an arithmetic/logic unit. The control unit controls and coordinates the actions of the other
29. 29. 1.2 What Is a Computer? 3 components. The arithmetic/logic unit performs numeric operations (addition, subtraction, multiplication, division) and logical operations (comparisons). Todays CPU is built on a small silicon semiconductor chip having millions of transistors. Every computer has an internal clock, which emits electronic pulses at a constant rate. These pulses are used to control and synchronize the pace of operations. The higher the clock speed, the more instructions are executed in a given period of time. The unit of measurement of clock speed is the hertz (Hz), with 1 hertz equaling 1 pulse per second. The clock speed of a computer is usually stated in megahertz (MHz) (1 MHz is 1 million Hz). CPU speed has been improved continuously. Intels Pentium 3 Processor runs at about 500 megahertz and Pentium 4 Processor at about 3 gigahertz (GHz) (1 GHz is 1000 MHz).speed hertz megahertz gigahertz1.2.2 Memory To store and process information, computers use off and on electrical states, referred to by convention as 0 and 1. These 0s and 1s are interpreted as digits in the binary number system and called bits (binary digits). Data of various kinds, such as numbers, characters, and strings, are encoded as series of bits. Data and program instructions for the CPU to execute are stored as groups of bits, or bytes, each byte composed of eight bits, in a computers memory. A memory unit is an ordered sequence of bytes, as shown in Figure 1.2. Memory address2000 2001 2002 2003 2004FIGURE 1.2bitbyteMemory content01001010 01100001 01110110 01100001 00000011Encoding for character J Encoding for character a Encoding for character v Encoding for character a Encoding for number 3Memory stores data and program instructions.The programmer need not be concerned about the encoding and decoding of data, which the system performs automatically, based on the encoding scheme. In the popular ASCII encoding scheme, for example, character 'J' is represented by 01001010 in one byte. A byte is the minimum storage unit. A small number such as 3 can be stored in a single byte. To store a number that cannot fit into a single byte, the computer uses several adjacent bytes. No two data items can share or split the same byte. A memory byte is never empty, but its initial content may be meaningless to your program. The current content of a memory byte is lost whenever new information is placed in it. A program and its data must be brought to memory before they can be executed. Every byte has a unique address. The address is used to locate the byte for storing and retrieving data. Since bytes can be accessed in any order, the memory is also referred to as random-access memory (RAM). Todays personal computers usually have at least 1 gigabyte of RAM. Computer storage size is measured in bytes, kilobytes (KB), megabytes (MB), gigabytes (GB), and terabytes (TB). A kilobyte is 210 = 1024, about 1000 bytes, a megabyte is 220 = 1048576, about 1 million bytes, a gigabyte is about 1 billion bytes, and a terabyte is about 1000 gigabytes. Like the CPU, memory is built on silicon semiconductor chips having thousands of transistors embedded on their surface. Compared to CPU chips, memory chips are less complicated, slower, and less expensive.RAM megabyte
30. 30. 4 Chapter 1 Introduction to Computers, Programs, and Java1.2.3Storage DevicesMemory is volatile, because information is lost when the power is turned off. Programs and data are permanently stored on storage devices and are moved, when the computer actually uses them, to memory, which is much faster than storage devices. There are four main types of storage devices: CD drives (CD-R, CD-RW, and DVD)Tape drivesdriveDisk drivesUSB flash drivesDrives are devices for operating a medium, such as disks, CDs, and tapes.Disks hard diskEach computer has at least one hard drive. Hard disks are for permanently storing data and programs. The hard disks of the latest PCs store from 80 to 250 gigabytes. Often disk drives are encased inside the computer. Removable hard disks are also available.CDs and DVDs CD-R CD-RWCD stands for compact disk. There are two types of CD drives: CD-R and CD-RW. A CD-R is for read-only permanent storage; the user cannot modify its contents once they are recorded. A CD-RW can be used like a hard disk and can be both read and rewritten. A single CD can hold up to 700 MB. Most software is distributed through CD-ROMs. Most new PCs are equipped with a CD-RW drive that can work with both CD-R and CD-RW. DVD stands for digital versatile disc or digital video disk. DVDs and CDs look alike, and you can use either to store data. A DVD can hold more information than a CD. A standard DVDs storage capacity is 4.7 GB.Tapes Tapes are mainly used for backup of data and programs. Unlike disks and CDs, tapes store information sequentially. The computer must retrieve information in the order it was stored. Tapes are very slow. It would take one to two hours to back up a 1-gigabyte hard disk. The new trend is to back up data using flash drives or external hard disks.USB Flash Drives USB flash drives are devices for storing and transporting data. A flash drive is smallabout the size of a pack of gum. It acts like a portable hard drive that can be plugged into your computers USB port. USB flash drives are currently available with up to 32 GB storage capacity.1.2.4Input and Output DevicesInput and output devices let the user communicate with the computer. The common input devices are keyboards and mice. The common output devices are monitors and printers.The Keyboardfunction key modifier keyA computer keyboard resembles a typewriter keyboard with extra keys added for certain special functions. Function keys are located at the top of the keyboard and are numbered with prefix F. Their use depends on the software. A modifier key is a special key (e.g., Shift, Alt, Ctrl) that modifies the normal action of another key when the two are pressed in combination.
31. 31. 1.3 Programs 5 The numeric keypad, located on the right-hand corner of the keyboard, is a separate set of keys for quick input of numbers. Arrow keys, located between the main keypad and the numeric keypad, are used to move the cursor up, down, left, and right. The Insert, Delete, Page Up, and Page Down keys, located above the arrow keys, are used in word processing for performing insert, delete, page up, and page down.numeric keypadThe Mouse A mouse is a pointing device. It is used to move an electronic pointer called a cursor around the screen or to click on an object on the screen to trigger it to respond.The Monitor The monitor displays information (text and graphics). The screen resolution and dot pitch determine the quality of the display. The screen resolution specifies the number of pixels per square inch. Pixels (short for picture elements) are tiny dots that form an image on the screen. A common resolution for a 17inch screen, for example, is 1024 pixels wide and 768 pixels high. The resolution can be set manually. The higher the resolution, the sharper and clearer the image is. The dot pitch is the amount of space between pixels in millimeters. The smaller the dot pitch, the better the display.1.2.5screen resolutiondot pitchCommunication DevicesComputers can be networked through communication devices, such as the dialup modem (modulator/demodulator), DSL, cable modem, network interface card, and wireless. A dialup modem uses a phone line and can transfer data at a speed up to 56,000 bps (bits per second). A DSL (digital subscriber line) also uses a phone line and can transfer data twenty times faster. A cable modem uses the TV cable line maintained by the cable company and is as fast as a DSL. A network interface card (NIC) is a device that connects a computer to a local area network (LAN). The LAN is commonly used in universities and business and government organizations. A typical NIC called 10BaseT can transfer data at 10 mbps (million bits per second). Wireless is becoming popular. Every laptop sold today is equipped with a wireless adapter that enables the computer to connect with the Internet.modem DSL NIC LAN mbps1.3 Programs Computer programs, known as software, are instructions to the computer, telling it what to do. Computers do not understand human languages, so you need to use computer languages in computer programs. Programming is the creation of a program that is executable by a computer and performs the required tasks. A computers native language, which differs among different types of computers, is its machine languagea set of built-in primitive instructions. These instructions are in the form of binary code, so in telling the machine what to do, you have to enter binary code. Programming in machine language is a tedious process. Moreover, the programs are highly difficult to read and modify. For example, to add two numbers, you might have to write an instruction in binary like this:software programmingmachine language1101101010011010Assembly language is a low-level programming language in which a mnemonic is used to represent each of the machine-language instructions. For example, to add two numbers, you might write an instruction in assembly code like this: ADDF3 R1, R2, R3assembly language
32. 32. 6 Chapter 1 Introduction to Computers, Programs, and Java assemblerAssembly languages were developed to make programming easy. However, since the computer cannot understand assembly language, a program called an assembler is used to convert assembly-language programs into machine code, as shown in Figure 1.3.Assembly Source File .. ADDF3 R1, R2, R3 ..FIGURE 1.3high-level languageMachine-Code FileAssembler.. 1101101010011010 ..Assembler translates assembly-language instructions to machine code.Assembly programs are written in terms of machine instructions with easy-to-remember mnemonic names. Since assembly language is machine dependent, an assembly program can be executed only on a particular kind of machine. The high-level languages were developed in order to transcend platform specificity and make programming easier. The high-level languages are English-like and easy to learn and program. Here, for example, is a high-level language statement that computes the area of a circle with radius 5: area = 5 * 5 * 3.1415;Among the more than one hundred high-level languages, the following are well known: COBOL (COmmon Business Oriented Language)FORTRAN (FORmula TRANslation)BASIC (Beginners All-purpose Symbolic Instruction Code)Pascal (named for Blaise Pascal)Ada (named for Ada Lovelace)C (developed by the designer of B)Visual Basic (Basic-like visual language developed by Microsoft)Delphi (Pascal-like visual language developed by Borland)C++ (an object-oriented language, based on C)C# (a Java-like language developed by Microsoft)JavaEach of these languages was designed for a specific purpose. COBOL was designed for business applications and is used primarily for business data processing. FORTRAN was designed for mathematical computations and is used mainly for numeric computations. BASIC was designed to be learned and used easily. Ada was developed for the Department of Defense and is used mainly in defense projects. C combines the power of an assembly language with the ease of use and portability of a high-level language. Visual Basic and Delphi are used in developing graphical user interfaces and in rapid application development. C++ is popular for system software projects such as writing compilers and operating systems. The Microsoft Windows operating system was coded using C++. C# (pronounced C sharp) is a new language developed by Microsoft for developing applications based on the Microsoft .NET platform. Java, developed by Sun Microsystems, is widely used for developing platform-independent Internet applications.
33. 33. 1.4 Operating Systems 7 A program written in a high-level language is called a source program or source code. Since a computer cannot understand a source program, a program called a compiler is used to translate it into a machine-language program. The machine-language program is then linked with other supporting library code to form an executable file, which can be run on the machine, as shown in Figure 1.4. On Windows, executable files have extension .exe.Source FileCompilerMachine-language FileLinkersource program compilerExecutable FileLibrary CodeFIGURE 1.4 A source program is compiled into a machine-language file, which is then linked with the system library to form an executable file.1.4 Operating Systems The operating system (OS) is the most important program that runs on a computer, which manages and controls a computers activities. The popular operating systems are Microsoft Windows, Mac OS, and Linux. Application programs, such as a Web browser or a word processor, cannot run without an operating system. The interrelationship of hardware, operating system, application software, and the user is shown in Figure 1.5.UserApplication ProgramsOperating SystemHardwareFIGURE 1.5The operating system is the software that controls and manages the system.The major tasks of an operating system are: Controlling and monitoring system activitiesAllocating and assigning system resourcesScheduling operations1.4.1 Controlling and Monitoring System Activities Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the monitor, keeping track of files and directories on the disk, and controlling peripheral devices, such as disk drives and printers. They also make sure that different programs and users running at the same time do not interfere with each other, and they are responsible for security, ensuring that unauthorized users do not access the system.OS
34. 34. 8 Chapter 1 Introduction to Computers, Programs, and Java1.4.2Allocating and Assigning System ResourcesThe operating system is responsible for determining what computer resources a program needs (e.g., CPU, memory, disks, input and output devices) and for allocating and assigning them to run the program.1.4.3multiprogrammingmultithreadingmultiprocessingScheduling OperationsThe OS is responsible for scheduling programs to make efficient use of system resources. Many of todays operating systems support such techniques as multiprogramming, multithreading, or multiprocessing to increase system performance. Multiprogramming allows multiple programs to run simultaneously by sharing the CPU. The CPU is much faster than the computers other components. As a result, it is idle most of the timefor example, while waiting for data to be transferred from the disk or from other sources. A multiprogramming OS takes advantage of this situation by allowing multiple programs to use the CPU when it would otherwise be idle. For example, you may use a word processor to edit a file at the same time as the Web browser is downloading a file. Multithreading allows concurrency within a program, so that its subtasks can run at the same time. For example, a word-processing program allows users to simultaneously edit text and save it to a file. In this example, editing and saving are two tasks within the same application. These two tasks may run on separate threads concurrently. Multiprocessing, or parallel processing, uses two or more processors together to perform a task. It is like a surgical operation where several doctors work together on one patient.1.5 Java, World Wide Web, and Beyond This book Gosling at embedded redesignedappletintroduces Java programming. Java was developed by a team led by James Sun Microsystems. Originally called Oak, it was designed in 1991 for use in chips in consumer electronic appliances. In 1995, renamed Java, it was for developing Internet applications. For the history of Java, see java.sun.com/features/1998/05/birthday.html. Java has become enormously popular. Its rapid rise and wide acceptance can be traced to its design characteristics, particularly its promise that you can write a program once and run it anywhere. As stated by Sun, Java is simple, object oriented, distributed, interpreted, robust, secure, architecture neutral, portable, high performance, multithreaded, and dynamic. For the anatomy of Java characteristics, see www.cs.armstrong.edu/liang/JavaCharacteristics.pdf. Java is a full-featured, general-purpose programming language that can be used to develop robust mission-critical applications. Today, it is employed not only for Web programming, but also for developing standalone applications across platforms on servers, desktops, and mobile devices. It was used to develop the code to communicate with and control the robotic rover on Mars. Many companies that once considered Java to be more hype than substance are now using it to create distributed applications accessed by customers and partners across the Internet. For every new project being developed today, companies are asking how they can use Java to make their work easier. The World Wide Web is an electronic information repository that can be accessed on the Internet from anywhere in the world. The Internet, the Webs infrastructure, has been around for more than thirty years. The colorful World Wide Web and sophisticated Web browsers are the major reason for the Internets popularity. The primary authoring language for the Web is the Hypertext Markup Language (HTML). HTML is a simple language for laying out documents, linking documents on the Internet, and bringing images, sound, and video alive on the Web. However, it cannot interact with the user except through simple forms. Web pages in HTML are essentially static and flat. Java initially became attractive because Java programs can be run from a Web browser. Such programs are called applets. Applets employ a modern graphical interface with buttons,
35. 35. 1.5 Java, World Wide Web, and Beyond 9 text fields, text areas, radio buttons, and so on, to interact with users on the Web and process their requests. Applets make the Web responsive, interactive, and fun to use. Figure 1.6 shows an applet running from a Web browser for playing a Tic Tac Toe game. Enter this URL from a Web browserFIGURE 1.6A Java applet for playing TicTacToe is embedded in an HTML page.Tip For a demonstration of Java applets, visit java.sun.com/applets. This site provides a rich Java resource as well as links to other cool applet demo sites. java.sun.com is the official Sun Java Website.Java can also be used to develop applications on the server side. These applications can be run from a Web server to generate dynamic Web pages. The automatic grading system for this book, as shown in Figure 1.7, was developed using Java. Enter this URL from a Web browserFIGURE 1.7Java was used to develop an automatic grading system to accompany this book.
36. 36. 10 Chapter 1 Introduction to Computers, Programs, and Java Java is a versatile programming language. You can use it to develop applications on your desktop and on the server. You can also use it to develop applications for small handheld devices. Figure 1.8 shows a Java-programmed calendar displayed on a BlackBerry and on a cell phone.FIGURE 1.8 Java can be used to develop applications for hand-held and wireless devices, such as a BlackBerry (left) and a cell phone (right).1.6 The Java Language Specification, API, JDK, and IDE Java language specificationAPIJava SE, EE, and MEJDK 1.6 = JDK 6Java IDEComputer languages have strict rules of usage. If you do not follow the rules when writing a program, the computer will be unable to understand it. The Java language specification and Java API define the Java standard. The Java language specification is a technical definition of the language that includes the syntax and semantics of the Java programming language. The complete Java language specification can be found at java.sun.com/docs/books/jls. The application program interface (API) contains predefined classes and interfaces for developing Java programs. The Java language specification is stable, but the API is still expanding. At the Sun Java Website (java.sun.com), you can view and download the latest version of the Java API. Java is a full-fledged and powerful language that can be used in many ways. It comes in three editions: Java Standard Edition (Java SE), Java Enterprise Edition (Java EE), and Java Micro Edition (Java ME). Java SE can be used to develop client-side standalone applications or applets. Java EE can be used to develop server-side applications, such as Java servlets and JavaServer Pages. Java ME can be used to develop applications for mobile devices, such as cell phones. This book uses Java SE to introduce Java programming. There are many versions of Java SE. The latest, Java SE 6, will be used in this book. Sun releases each version with a Java Development Toolkit (JDK). For Java SE 6, the Java Development Toolkit is called JDK 1.6 (also known as Java 6 or JDK 6). JDK consists of a set of separate programs, each invoked from a command line, for developing and testing Java programs. Besides JDK, you can use a Java development tool (e.g., NetBeans, Eclipse, and TextPad)software that provides an integrated development environment (IDE) for rapidly developing Java programs. Editing, compiling, building, debugging, and
37. 37. 1.7 A Simple Java Program 11 online help are integrated in one graphical user interface. Just enter source code in one window or open an existing file in a window, then click a button, menu item, or function key to compile and run the program.1.7 A Simple Java Program Let us begin with a simple Java program that displays the message Welcome to Java! on the console. Console refers to text entry and display device of a computer. The program is shown in Listing 1.1.consoleLISTING 1.1 Welcome.javaVideo Note First Java program1 public class Welcome { 2 public static void main(String[] args) { 3 // Display message Welcome to Java! to the console 4 System.out.println("Welcome to Java!"); 5 } 6 }class main method display messageWelcome to Java!The line numbers are displayed for reference purposes but are not part of the program. So, dont type line numbers in your program. Line 1 defines a class. Every Java program must have at least one class. Each class has a name. By convention, class names start with an uppercase letter. In this example, the class name is Welcome. Line 2 defines the main method. In order to run a class, the class must contain a method named main. The program is executed from the main method. A method is a construct that contains statements. The main method in this program contains the System.out.println statement. This statement prints a message "Welcome to Java!" to the console (line 4). Every statement in Java ends with a semicolon (;), known as the statement terminator. Reserved words, or keywords, have a specific meaning to the compiler and cannot be used for other purposes in the program. For example, when the compiler sees the word class, it understands that the word after class is the name for the class. Other reserved words in this program are public, static, and void. Line 3 is a comment that documents what the program is and how it is constructed. Comments help programmers to communicate and understand the program. They are not programming statements and thus are ignored by the compiler. In Java, comments are preceded by two slashes (//) on a line, called a line comment, or enclosed between /* and */ on one or several lines, called a block comment. When the compiler sees //, it ignores all text after // on the same line. When it sees /*, it scans for the next */ and ignores any text between /* and */. Here are examples of comments:line numbersclass name main methodstatement terminator reserved wordcomment// This application program prints Welcome to Java! /* This application program prints Welcome to Java! */ /* This application program prints Welcome to Java! */A pair of braces in a program forms a block that groups the programs components. In Java, each block begins with an opening brace ({) and ends with a closing brace (}). Every class has a class block that groups the data and methods of the class. Every method has a methodblock
38. 38. 12 Chapter 1 Introduction to Computers, Programs, and Java block that groups the statements in the method. Blocks can be nested, meaning that one block can be placed within another, as shown in the following code. public class Welcome { public static void main(String[] args) { Class block System.out.println("Welcome to Java!"); Method block } }Tip matching bracesAn opening brace must be matched by a closing brace. Whenever you type an opening brace, immediately type a closing brace to prevent the missing-brace error. Most Java IDEs automatically insert the closing brace for each opening brace.Note You are probably wondering why the main method is declared this way and why System.out.println(...) is used to display a message to the console. For the time being, simply accept that this is how things are done. Your questions will be fully answered in subsequent chapters.Caution case sensitiveJava source programs are case sensitive. It would be wrong, for example, to replace main in the program with Main.Note syntax rulesLike any programming language, Java has its own syntax, and you need to write code that obeys the syntax rules. If your program violates the rulesfor example if the semicolon is missing, a brace is missing, a quotation mark is missing, or String is misspelledthe Java compiler will report syntax errors. Try to compile the program with these errors and see what the compiler reports.The program in Listing 1.1 displays one message. Once you understand the program, it is easy to extend it to display more messages. For example, you can rewrite the program to display three messages, as shown in Listing 1.2.LISTING 1.2 Welcome1.java class main method display message1 public class Welcome1 { 2 public static void main(String[] args) { 3 System.out.println("Programming is fun!"); 4 System.out.println("Fundamentals First"); 5 System.out.println("Problem Driven"); 6 } 7 }Programming is fun! Fundamentals First Problem DrivenFurther, you can perform mathematical computations and display the result to the console. 10.5 + 2 * 3 Listing 1.3 gives an example of evaluating . 45 - 3.5
39. 39. 1.8 Creating, Compiling, and Executing a Java Program 13LISTING 1.3 ComputeExpression.java 1 public class ComputeExpression { 2 public static void main(String[] args) { 3 System.out.println((10.5 + 2 * 3) / (45 3.5)); 4 } 5 }class main method compute expression0.39759036144578314The multiplication operator in Java is *. As you see, it is a straightforward process to translate an arithmetic expression to a Java expression. We will discuss Java expressions further in Chapter 2.1.8 Creating, Compiling, and Executing a Java Program You have to create your program and compile it before it can be executed. This process is repetitive, as shown in Figure 1.9. If your program has compilation errors, you have to modify the program to fix them, then recompile it. If your program has runtime errors or does not produce the correct result, you have to modify the program, recompile it, and execute it again.Create/Modify Source Code Source code (developed by the programmer) Saved on the disk public class Welcome { public static void main(String[] args) { System.out.println("Welcome to Java!"); Source Code } }Bytecode (generated by the compiler for JVM to read and interpret, not for you to understand) Method Welcome() 0 aload_0 Method void main(java.lang.String[]) 0 getstatic #2 3 ldc #3 5 invokevirtual #4 8 returnCompile Source Code e.g., javac Welcome.java If compilation errors Stored on the disk BytecodeRun Bytecode e.g., java WelcomeWelcome to Java is printed on the console Welcome to Java!Result If runtime errors or incorrect resultFIGURE 1.9 The Java program-development process consists of repeatedly creating/modifying source code, compiling, and executing programs.
40. 40. 14 Chapter 1 Introduction to Computers, Programs, and Java You can use any text editor or IDE to create and edit a Java source-code file. This section demonstrates how to create, compile, and run Java programs from a command window. If you wish to use an IDE such as Eclipse, NetBeans, or TextPad, please refer to Supplement II for tutorials. From the command window, you can use the NotePad to create the Java source code file, as shown in Figure 1.10.editorVideo Note Brief Eclipse TutorialFIGURE 1.10You can create the Java source file using Windows NotePad.Note The source file must end with the extension .java and must have exactly the same name as the public class name. For example, the file for the source code in Listing 1.1 should be named Welcome.java, since the public class name is Welcome.file nameA Java compiler translates a Java source file into a Java bytecode file. The following command compiles Welcome.java: javac Welcome.javacompileNote You must first install and configure JDK before compiling and running programs. See Supplement I.B, Installing and Configuring JDK 6, on how to install JDK and set up the environment to compile and run Java programs. If you have trouble compiling and running programs, please see Supplement I.C, Compiling and Running Java from the Command Window. This supplement also explains how to use basic DOS commands and how to use Windows NotePad and WordPad to create and edit files. All the supplements are accessible from the Companion Website.Supplement I.BSupplement I.CIf there are no syntax errors, the compiler generates a bytecode file with a .class extension. So the preceding command generates a file named Welcome. class, as shown in Figure 1.11(a). The Java language is a high-level language while Java bytecode is a low-level language. The bytecode is similar to machine instructions but is architecture neutral and can run on any platform that has a Java Virtual Machine (JVM), as shown in Figure 1.11(b). Rather than a physical machine, the virtual machine is a program that interprets Java bytecode. This is one of Javas primary advantages: Java bytecode can run on a variety of hardware platforms and operating systems..class bytecode filecompiled byJava Compiler(a)generatesWelcome.class (Java bytecode executable file)JVM executed byirtual Mach aVe inWelcome.java (Java source code file)JavBytecode JavaAny Computer(b)FIGURE 1.11 (a) Java source code is translated into bytecode. (b) Java bytecode can be executed on any computer with a Java Virtual Machine.
41. 41. 1.8 Creating, Compiling, and Executing a Java Program 15 To execute a Java program is to run the programs bytecode. You can execute the bytecode on any platform with a JVM. Java bytecode is interpreted. Interpreting translates the individual steps in the bytecode into the target machine-language code one at a time rather than translating the whole program as a single unit. Each step is executed immediately after it is translated. The following command runs the bytecode: java Welcomeinterpreting bytecoderunFigure 1.12 shows the javac command for compiling Welcome.java. The compiler generated the Welcome.class file. This file is executed using the java command.CompileVideo Note Compile and run a Java programShow filesRunFIGURE 1.12The output of Listing 1.1 displays the message Welcome to Java!Note For simplicity and consistency, all source code and class files are placed under c:book unless specified otherwise.c:bookCaution Do not use the extension .class in the command line when executing the program. Use java ClassName to run the program. If you use java ClassName.class in the command line, the system will attempt to fetch ClassName.class.class.java ClassNameTip If you execute a class file that does not exist, a NoClassDefFoundError will occur. If you execute a class file that does not have a main method or you mistype the main method (e.g., by typing Main instead of main), a NoSuchMethodError will occur.NoClassDefFoundError NoSuchMethodErrorNote When executing a Java program, the JVM first loads the bytecode of the class to memory using a program called the class loader. If your program uses other classes, the class loader dynamically loads them just before they are needed. After a class is loaded, the JVM uses a program called bytecode verifier to check the validity of the bytecode and ensure that the bytecode does not violate Javas security restrictions. Java enforces strict security to make sure that Java programs arriving from the network do not harm your computer.class loader bytecode verifier
42. 42. 16 Chapter 1 Introduction to Computers, Programs, and Java Pedagogical Note Instructors may require students to use packages for organizing programs. For example, you may place all programs in this chapter in a package named chapter1. For instructions on how to use packages, please see Supplement I.F, Using Packages to Organize the Classes in the Text.using package1.9 (GUI) Displaying Text in a Message Dialog Box JOptionPane showMessageDialogThe program in Listing 1.1 displays the text on the console, as shown in Figure 1.12. You can rewrite the program to display the text in a message dialog box. To do so, you need to use the showMessageDialog method in the JOptionPane class. JOptionPane is one of the many predefined classes in the Java system that you can reuse rather than reinventing the wheel. You can use the showMessageDialog method to display any text in a message dialog box, as shown in Figure 1.13. The new program is given in Listing 1.4. Title Title bar Message Click the OK button to dismiss the dialog boxFIGURE 1.13Welcome to Java! is displayed in a message box.LISTING 1.4 WelcomeInMessageDialogBox.java block commentimportmain method display messagepackage1 2 3 4 5 6 7 8 9 10 11/* This application program displays Welcome to Java! * in a message dialog box. */ import javax.swing.JOptionPane; public class WelcomeInMessageDialogBox { public static void main(String[] args) { // Display Welcome to Java! in a message dialog box JOptionPane.showMessageDialog(null, "Welcome to Java!"); } }This program uses a Java class JOptionPane (line 9). Javas predefined classes are grouped into packages. JOptionPane is in the javax.swing package. JOptionPane is imported to the program using the import statement in line 4 so that the compiler can locate the class without the full name javax.swing.JOptionPane.Note If you replace JOptionPane on line 9 with javax.swing.JOptionPane, you dont need to import it in line 4. javax.swing.JOptionPane is the full name for the JOptionPane class.The showMessageDialog method is a static method. Such a method should be invoked by using the class name followed by a dot operator (.) and the method name with arguments. Methods will be introduced in Chapter 5, Methods. The showMessageDialog method can be invoked with two arguments, as shown below. JOptionPane.showMessageDialog(null, "Welcome to Java!");
43. 43. Key Terms 17 The first argument can always be null. null is a Java keyword that will be fully introduced in Chapter 8, Objects and Classes. The second argument is a string for text to be displayed. There are several ways to use the showMessageDialog method. For the time being, you need to know only two ways. One is to use a statement, as shown in the example:two versions of showMessageDialogJOptionPane.showMessageDialog(null, x);where x is a string for the text to be displayed. The other is to use a statement like this one: JOptionPane.showMessageDialog(null, x, y, JOptionPane.INFORMATION_MESSAGE);where x is a string for the text to be displayed, and y is a string for the title of the message box. The fourth argument can be JOptionPane.INFORMATION_MESSAGE, which causes the icon ( ) to be displayed in the message box, as shown in the following example.JOptionPane.showMessageDialog(null, "Welcome to Java!", "Display Message", JOptionPane.INFORMATION_MESSAGE);Note There are two types of import statements: specific import and wildcard import. The specific import specifies a single class in the import statement. For example, the following statement imports JOptionPane from package javax.swing.specific importimport javax.swing.JOptionPane;The wildcard import imports all the classes in a package. For example, the following statement imports all classes from package javax.swing.wildcard importimport javax.swing.*;The information for the classes in an imported package is not read in at compile time or runtime unless the class is used in the program. The import statement simply tells the compiler where to locate the classes. There is no performance difference between a specific import and a wildcard import declaration.no performance differenceNote Recall that you have used the System class in the statement System.out.println(Welcome to Java); in Listing 1.1. The System class is not imported because it is in the java.lang package. All the classes in the java.lang package are implicitly imported in every Java program.KEY TERMS .class file 14 .java file 14 assembly language 5 bit 3 block 12 block comment 11 bus 2byte 3 bytecode 14 bytecode verifier 15 cable modem 5 central processing unit (CPU) class loader 15 comment 112java.langimplicitly imported
44. 44. 18 Chapter 1 Introduction to Computers, Programs, and Java compiler 7 console 11 dot pitch 5 DSL (digital subscriber line) 5 hardware 2 high-level language 6 Integrated Development Environment (IDE) 10 java command 15 javac command 15 Java Development Toolkit (JDK) 10 Java Virtual Machine (JVM) 14 keyword (or reserved word) 11 line comment 11 machine language 5 main method 11memory 3 modem 5 network interface card (NIC) operating system (OS) 7 pixel 5 program 5 programming 5 resolution 5 software 5 source code 7 source file 14 specific import 17 storage devices 4 statement 11 wildcard import 175Note Supplement I.AThe above terms are defined in the present chapter. Supplement I.A, Glossary, lists all the key terms and descriptions in the book, organized by chapters.CHAPTER SUMMARY 1. A computer is an electronic device that stores and processes data. 2. A computer includes both hardware and software. 3. Hardware is the physical aspect of the computer that can be seen. 4. Computer programs, known as software, are the invisible instructions that control the hardware and make it perform tasks.5. Computer programming is the writing of instructions (i.e., code) for computers to perform.6. The central processing unit (CPU) is a computers brain. It retrieves instructions from memory and executes them.7. Computers use zeros and ones because digital devices have two stable states, referred to by convention as zero and one.8. A bit is a binary digit 0 or 1. 9. A byte is a sequence of 8 bits. 10. A kilobyte is about 1000 bytes, a megabyte about 1 million bytes, a gigabyte about 1 billion bytes, and a terabyte about 1000 gigabytes.11. Memory stores data and program instructions for the CPU to execute. 12. A memor