A Programmer’s Guide to Java™ SCJP Certification Third Edition

A Programmer’s Guide to Java™ SCJP Certification Third Edition This page intentionally left blank A Programmer’s Guide to Java™ SCJP Certification A Comprehensive Primer Third Edition Khalid A. Mughal Rolf W. Rasmussen Upper Saddle River, New Jersey • Boston • Indianapolis • San Francisco New York • Toronto • Montreal • London • Munich • Paris • Madrid Capetown • Sidney • Tokyo • Singapore • Mexico City Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed with initial capital letters or in all capitals. The authors and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of the use of the information or programs contained herein. The publisher offers excellent discounts on this book when ordered in quantity for bulk purchases or special sales, which may include electronic versions and/or custom covers and content particular to your business, training goals, marketing focus, and branding interests. For more information, please contact: U.S. Corporate and Government Sales (800) 382-3419 For sales outside the United States please contact: International Sales Visit us on the Web: Library of Congress Cataloging-in-Publication Data Mughal, Khalid Azim. A programmer's guide to Java SCJP certification : a comprehensive primer / Khalid A. Mughal, Rolf W. Rasmussen.—3rd ed. p. cm. Previously published under title: A programmer’s guide to Java certification. Includes bibliographical references and index. ISBN 0-321-55605-4 (pbk. : alk. paper) 1. Electronic data processing personnel--Certification. 2. Operating systems (Computers)—Examinations--Study guides. 3. Java (Computer program language)--Examinations-- Study guides. I. Rasmussen, Rolf (Rolf W.) II. Mughal, Khalid Azim. Programmer’s guide to Java certification. III. Title. QA76.3.M846 2008 005.2'762--dc22 2 Copyright © 2009 Pearson Education, Inc. All rights reserved. Printed in the United States of America. This publication is protected by copyright, and permission must 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. For information regarding permissions, write to: ISBN-13: 978-0-321-55605-9 ISBN-10: 0-321-55605-4 Text printed in the United States on recycled paper at Courierin Stoughton, Massachusetts. First printing, December 2008 To the loving memory of my mother, Zubaida Begum, and my father, Mohammed Azim. —K.A.M. For Olivia E. Rasmussen and Louise J. Dahlmo. —R.W.R. This page intentionally left blank Contents Overview Foreword xxxv Preface xxxvii 1 Basics of Java Programming 1 2 Language Fundamentals 19 3 Declarations 39 4 Access Control 103 5 Operators and Expressions 159 6 Control Flow 203 7 Object-Oriented Programming 283 8 Nested Type Declarations 351 9 Object Lifetime 389 10 Fundamental Classes 423 11 Files and Streams 467 12 Localization, Pattern Matching and Formatting 531 13 Threads 613 14 Generics 661 vii viii CONTENTS 15 Collections and Maps 747 A Taking the SCJP 1.6 Exam 851 B Objectives for the SCJP 1.6 Exam 857 C Objectives for the SCJP 1.6 Upgrade Exam 863 D Annotated Answers to Review Questions 869 E Solutions to Programming Exercises 935 F Mock Exam 959 G Number Systems and Number Representation 1005 Index 1013 Contents List of Figures xxiii List of Tables xxvii List of Examples xxix Foreword xxxv Preface xxxvii 1 Basics of Java Programming 1 1.1 Introduction 2 1.2 Classes 2 Declaring Members: Fields and Methods 3 1.3 Objects 4 Class Instantiation, Reference Values, and References 4 Object Aliases 6 1.4 Instance Members 6 Invoking Methods 7 1.5 Static Members 7 1.6 Inheritance 10 1.7 Aggregation 12 1.8 Tenets of Java 13 Review Questions 13 1.9 Java Programs 15 1.10 Sample Java Application 15 Essential Elements of a Java Application 15 Compiling and Running an Application 16 Review Questions 17 Chapter Summary 18 Programming Exercise 18 ix x CONTENTS 2 Language Fundamentals 19 2.1 Basic Language Elements 20 Lexical Tokens 20 Identifiers 20 Keywords 20 Literals 21 Integer Literals 22 Floating-Point Literals 22 Boolean Literals 23 Character Literals 23 String Literals 25 White Spaces 25 Comments 26 Review Questions 27 2.2 Primitive Data Types 28 Integer Types 28 The char Type 29 The Floating-Point Types 29 The boolean Type 30 Review Questions 31 2.3 Variable Declarations 31 Declaring and Initializing Variables 31 Reference Variables 32 2.4 Initial Values for Variables 33 Default Values for Fields 33 Initializing Local Variables of Primitive Data Types 34 Initializing Local Reference Variables 35 Lifetime of Variables 35 Review Questions 36 Chapter Summary 37 Programming Exercise 37 3 Declarations 39 3.1 Class Declarations 40 3.2 JavaBeans Standard 41 Naming Patterns for Properties 41 Naming Patterns for the Event Model 42 3.3 Method Declarations 44 Statements 45 Instance Methods and the Object Reference this 45 Method Overloading 47 3.4 Constructors 48 The Default Constructor 49 Overloaded Constructors 51 Review Questions 52 CONTENTS xi 3.5 Enumerated Types 54 Declaring Typesafe Enums 54 Using Typesafe Enums 54 Declaring Enum Constructors and Members 55 Implicit Static Methods for Enum Types 57 Inherited Methods from the Enum Class 58 Extending Enum Types: Constant-Specific Class Bodies 59 Declaring Typesafe Enums Revisited 62 Review Questions 63 3.6 Arrays 69 Declaring Array Variables 70 Constructing an Array 70 Initializing an Array 71 Using an Array 72 Anonymous Arrays 74 Multidimensional Arrays 75 Review Questions 79 3.7 Parameter Passing 81 Passing Primitive Data Values 82 Passing Reference Values 84 Passing Arrays 86 Array Elements as Actual Parameters 87 final Parameters 89 3.8 Variable Arity Methods 90 Calling a Varargs Method 91 Varargs and Non-Varargs Method Calls 93 3.9 The main() Method 94 Program Arguments 95 Review Questions 96 Chapter Summary 100 Programming Exercises 101 4 Access Control 103 4.1 Java Source File Structure 104 4.2 Packages 105 Defining Packages 106 Using Packages 107 Compiling Code into Packages 115 Running Code from Packages 117 4.3 Searching for Classes 117 4.4 The JAR Utility 120 4.5 System Properties 122 Review Questions 123 4.6 Scope Rules 129 Class Scope for Members 129 xii CONTENTS Block Scope for Local Variables 131 4.7 Accessibility Modifiers for Top-Level Type Declarations 132 4.8 Other Modifiers for Classes 135 abstract Classes 135 final Classes 136 Review Questions 138 4.9 Member Accessibility Modifiers 138 public Members 139 protected Members 141 Default Accessibility for Members 142 private Members 143 Review Questions 144 4.10 Other Modifiers for Members 146 static Members 147 final Members 148 abstract Methods 150 synchronized Methods 150 native Methods 151 transient Fields 152 volatile Fields 153 Review Questions 154 Chapter Summary 157 Programming Exercise 157 5 Operators and Expressions 159 5.1 Conversions 160 Widening and Narrowing Primitive Conversions 160 Widening and Narrowing Reference Conversions 161 Boxing and Unboxing Conversions 162 Other Conversions 162 5.2 Type Conversion Contexts 163 Assignment Context 164 Method Invocation Context 164 Casting Context of the Unary Type Cast Operator: (type) 164 Numeric Promotion Context 165 5.3 Precedence and Associativity Rules for Operators 166 5.4 Evaluation Order of Operands 168 Left-Hand Operand Evaluation First 168 Operand Evaluation before Operation Execution 168 Left to Right Evaluation of Argument Lists 169 5.5 The Simple Assignment Operator = 169 Assigning Primitive Values 169 Assigning References 169 Multiple Assignments 170 Type Conversions in Assignment Context 171 CONTENTS xiii Review Questions 173 5.6 Arithmetic Operators: *, /, %, +, - 174 Arithmetic Operator Precedence and Associativity 174 Evaluation Order in Arithmetic Expressions 174 Range of Numeric Values 175 Unary Arithmetic Operators: -, + 177 Multiplicative Binary Operators: *, /, % 178 Additive Binary Operators: +, - 180 Numeric Promotions in Arithmetic Expressions 180 Arithmetic Compound Assignment Operators: *=, /=, %=, +=, -= 182 Review Questions 184 5.7 The Binary String Concatenation Operator + 185 5.8 Variable Increment and Decrement Operators: ++, -- 186 The Increment Operator ++ 187 The Decrement Operator -- 187 Review Questions 188 5.9 Boolean Expressions 190 5.10 Relational Operators: <, <=, >, >= 190 5.11 Equality 191 Primitive Data Value Equality: ==, != 191 Object Reference Equality: ==, != 192 Object Value Equality 193 5.12 Boolean Logical Operators: !, ^, &, | 194 Operand Evaluation for Boolean Logical Operators 195 Boolean Logical Compound Assignment Operators: &=, ^=, |= 195 5.13 Conditional Operators: &&, || 196 Short-Circuit Evaluation 197 Review Questions 199 5.14 The Conditional Operator: ?: 201 5.15 Other Operators: new, [], instanceof 201 Chapter Summary 202 Programming Exercise 202 6 Control Flow 203 6.1 Overview of Control Fl