EditionFifth

Learning Java An Introduction to Real-World Programming with Java

Marc Loy, Patrick Niemeyer & Daniel Leuck

FIFTH EDITION Learning Java An Introduction to Real-World Programming with Java

Marc Loy, Patrick Niemeyer, and Daniel Leuck

Beijing Boston Farnham Sebastopol Tokyo Learning Java by Marc Loy, Patrick Niemeyer, and Daniel Leuck Copyright © 2020 Marc Loy, Patrick Niemeyer, Daniel Leuck. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (http://oreilly.com). For more information, contact our corporate/institutional sales department: 800-998-9938 or [email protected].

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May 2000: First Edition July 2002: Second Edition May 2005: Third Edition June 2013: Fourth Edition March 2020: Fifth Edition

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978-1-492-05627-0 [LSI] Table of Contents

Preface...... xi

1. A Modern Language...... 1 Enter Java 2 Java’s Origins 2 Growing Up 3 A Virtual Machine 4 Java Compared with Other Languages 7 Safety of Design 10 Simplify, Simplify, Simplify… 11 Type Safety and Method Binding 12 Incremental Development 13 Dynamic Memory Management 13 Error Handling 14 Threads 15 Scalability 15 Safety of Implementation 16 The Verifier 17 Class Loaders 19 Security Managers 19 Application and User-Level Security 20 A Java Road Map 21 The Past: Java 1.0–Java 11 21 The Present: Java 14 23 The Future 25 Availability 25

iii 2. A First Application...... 27 Java Tools and Environment 28 Installing the JDK 28 Installing OpenJDK on Linux 29 Installing OpenJDK on macOS 30 Installing OpenJDK on Windows 31 Configuring IntelliJ IDEA and Creating a Project 35 Running the Project 39 Grabbing the Learning Java Examples 39 HelloJava 41 Classes 44 The main() Method 44 Classes and Objects 46 Variables and Class Types 46 HelloComponent 47 Inheritance 48 The JComponent Class 49 Relationships and Finger-Pointing 50 Package and Imports 51 The paintComponent() Method 52 HelloJava2: The Sequel 53 Instance Variables 55 Constructors 56 Events 58 The repaint() Method 60 Interfaces 60 Goodbye and Hello Again 62

3. Tools of the Trade...... 63 JDK Environment 63 The Java VM 64 Running Java Applications 64 System Properties 66 The Classpath 66 javap 68 Modules 68 The Java Compiler 69 Trying Java 70 JAR Files 77 File Compression 77 The jar Utility 77 The pack200 Utility 80

iv | Table of Contents Building Up 81

4. The Java Language...... 83 Text Encoding 84 Comments 86 Javadoc Comments 87 Variables and Constants 89 Types 90 Primitive Types 91 Reference Types 95 Inferring Types 97 Passing References 97 A Word About Strings 98 Statements and Expressions 99 Statements 100 Expressions 108 Arrays 114 Array Types 115 Array Creation and Initialization 115 Using Arrays 117 Anonymous Arrays 119 Multidimensional Arrays 119 Types and Classes and Arrays, Oh My! 121

5. Objects in Java...... 123 Classes 124 Declaring and Instantiating Classes 125 Accessing Fields and Methods 127 Static Members 131 Methods 134 Local Variables 135 Shadowing 135 Static Methods 137 Initializing Local Variables 139 Argument Passing and References 140 Wrappers for Primitive Types 141 Method Overloading 143 Object Creation 145 Constructors 145 Working with Overloaded Constructors 146 Object Destruction 148 Garbage Collection 148

Table of Contents | v Packages 149 Importing Classes 150 Custom Packages 151 Member Visibility and Access 153 Compiling with Packages 155 Advanced Class Design 155 Subclassing and Inheritance 156 Interfaces 161 Inner Classes 163 Anonymous Inner Classes 165 Organizing Content and Planning for Failure 167

6. Error Handling and Logging...... 169 Exceptions 170 Exceptions and Error Classes 170 Exception Handling 172 Bubbling Up 175 Stack Traces 176 Checked and Unchecked Exceptions 177 Throwing Exceptions 178 try Creep 182 The finally Clause 183 try with Resources 184 Performance Issues 185 Assertions 186 Enabling and Disabling Assertions 187 Using Assertions 188 The Logging API 189 Overview 189 Logging Levels 191 A Simple Example 192 Logging Setup Properties 193 The Logger 195 Performance 195 Real-World Exceptions 196

7. Collections and Generics...... 197 Collections 197 The Collection Interface 198 Collection Types 199 The Map Interface 201 Type Limitations 203

vi | Table of Contents Containers: Building a Better Mousetrap 203 Can Containers Be Fixed? 205 Enter Generics 205 Talking About Types 208 “There Is No Spoon” 209 Erasure 210 Raw Types 211 Parameterized Type Relationships 213 Why Isn’t a List a List