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Learning Java by Marc Loy, Patrick Niemeyer and Daniel Leuck

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By Marc Loy, Patrick Niemeyer, and Daniel Leuck

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

Web page for this book where they list errata and any additional information. You can access this page at https://oreil.ly/Java_5e.

Preface

This book is about the Java programming language and environment. Whether you are a software developer or just someone who uses the internet in your daily life, you’ve undoubtedly heard about Java. Its introduction was one of the most exciting developments in the history of the web, and Java applications have powered much of the growth of business on the internet. Java is, arguably, the most popular programming language in the world, used by millions of developers on almost every kind of computer imaginable. Java has surpassed languages such as C++ and Visual Basic in terms of developer demand and has become the de facto language for certain kinds of development — especially for web-based services. Most universities are now using Java in their introductory courses alongside the other important modern languages. Perhaps you are using this text in one of your classes right now!

This book gives you a thorough grounding in Java fundamentals and APIs. Learning Java, Fifth Edition, attempts to live up to its name by mapping out the Java language and its class libraries, programming techniques, and idioms. We’ll dig deep into interesting areas and at least scratch the surface of other popular topics. Other titles from O’Reilly pick up where we leave off and provide more comprehensive information on specific areas and applications of Java.

Whenever possible, we provide compelling, realistic, and fun examples and avoid merely cataloging features. The examples are simple, but hint at what can be done. We won’t be developing the next great “killer app” in these pages, but we hope to give you a starting point for many hours of experimentation and inspired tinkering that will lead you to develop one yourself.

Who Should Read This Book

This book is for computer professionals, students, technical people, and Finnish hackers. It’s for everyone who has a need for hands-on experience with the Java language with an eye toward building real applications. This book could also be considered a crash course in object-oriented programming, networking, and user interfaces. As you learn about Java, you’ll also learn a powerful and practical approach to software development, beginning with a deep understanding of the fundamentals of Java and its APIs.

Superficially, Java looks like C or C++, so you’ll have a tiny headstart in using this book if you have some experience with one of these languages. If you do not, don’t worry. Don’t make too much of the syntactic similarities between Java and C or C++. In many respects, Java acts like more dynamic languages such as Smalltalk and Lisp. Knowledge of another object-oriented programming language should certainly help, although you may have to change some ideas and unlearn a few habits. Java is considerably simpler than languages such as C++ and Smalltalk. If you learn well from concise examples and personal experimentation, we think you’ll like this book.

The last part of this book branches out to discuss Java in the context of web applications, web services, and request processing, so you should be familiar with the basic ideas behind web browsers, servers, and documents.

New Developments

This edition of Learning Java is actually the seventh edition — updated and retitled — of our original, popular Exploring Java. With each edition, we’ve taken great care not only to add new material covering additional features, but to thoroughly revise and update the existing content to synthesize the coverage and add years of real-world perspective and experience to these pages.

One noticeable change in recent editions is that we’ve de-emphasized the use of applets, reflecting their diminished role in recent years in creating interactive web pages. In contrast, we’ve greatly expanded our coverage of Java web applications and web services, which are now mature technologies.

We cover all of the important features of the latest “long-term support” release of Java, officially called Java Standard Edition (SE) 11, OpenJDK 11, but we also add in a few details from the “feature” releases of Java 12, Java 13, and Java 14. Sun Microsystems (Java’s keeper before Oracle) has changed the naming scheme many times over the years. Sun coined the term Java 2 to cover the major new features introduced in Java version 1.2 and dropped the term JDK in favor of SDK. With the sixth release, Sun skipped from Java version 1.4 to Java 5.0, but reprieved the term JDK and kept its numbering convention there. After that, we had Java 6, Java 7, and so on, and now we are at Java 14.

This release of Java reflects a mature language with occasional syntactic changes and updates to APIs and libraries. We’ve tried to capture these new features and update every example in this book to reflect not only the current Java practice, but style as well.

New in This Edition (Java 11, 12, 13, 14)

This edition of the book continues our tradition of rework to be as complete and up-to-date as possible. It incorporates changes from both the Java 11 — again, the long-term support version — and Java 12, 13, and 14 feature releases. (More on the specifics of the Java features included and excluded in recent releases in Chapter 13.) New topics in this edition include:

New language features, including type inference in generics and improved exception handling and automatic resource management syntax

New interactive playground, jshell, for trying out code snippets

The proposed switch expression

Basic lambda expressions

Updated examples and analysis throughout the book

Using This Book

This book is organized roughly as follows:

Chapters 1 and 2 provide a basic introduction to Java concepts and a tutorial to give you a jump-start on Java programming.

Chapter 3 discusses fundamental tools for developing with Java (the compiler, the interpreter, jshell, and the JAR file package).

Chapters 4 and 5 introduce programming fundamentals, then describe the Java language itself, beginning with the basic syntax and then covering classes and objects, exceptions, arrays, enumerations, annotations, and much more.

Chapter 6 covers exceptions, errors, and the logging facilities native to Java.

Chapter 7 covers collections alongside generics and parameterized types in Java.

Chapter 8 covers text processing, formatting, scanning, string utilities, and much of the core API utilities.

Chapter 9 covers the language’s built-in thread facilities.

Chapter 10 covers the basics of graphical user interface (GUI) development with Swing.

Chapter 11 covers Java I/O, streams, files, sockets, networking, and the NIO package.

Chapter 12 covers web applications using servlets, servlet filters, and WAR files, as well as web services.

Chapter 13 introduces the Java Community Process and highlights how to track future changes to Java while helping you retrofit existing code with new features, such as the lambda expressions introduced in Java 8.

If you’re like us, you don’t read books from front to back. If you’re really like us, you usually don’t read the preface at all. However, on the off chance that you will see this in time, here are a few suggestions:

If you are already a programmer and just need to learn Java in the next five minutes, you are probably looking for the examples. You might want to start by glancing at the tutorial in Chapter 2. If that doesn’t float your boat, you should at least look at the information in Chapter 3, which explains how to use the compiler and interpreter. This should get you started.

Chapters 11 and 12 are the places to head if you are interested in writing network or web-based applications and services. Networking remains one of the more interesting and important parts of Java.

Chapter 10 discusses Java’s graphics features and component architecture. You should read this if you are interested in writing desktop graphical Java applications.

Chapter 13 discusses how to stay on top of changes to the Java language itself, regardless of your particular focus.

Online Resources

There are many online sources for information about Java.

Oracle’s official website for Java topics is https://oreil.ly/Lo8QZ; look here for the software, updates, and Java releases. This is where you’ll find the reference implementation of the JDK, which includes the compiler, the interpreter, and other tools.

Oracle also maintains the OpenJDK site. This is the primary open source version of Java and the associated tools. We’ll be using the OpenJDK for all the examples in this book.

You should also visit O’Reilly’s site at http://oreilly.com/. There you’ll find information about other O’Reilly books for both Java and a growing array of other topics. You should also check out the online learning and conference options — O’Reilly is a real champion for education in all its forms.

And of course, you can check the home page for Learning Java!

Conventions Used in This Book

The font conventions used in this book are quite simple.

Italic is used for:

Pathnames, filenames, and program names

Internet addresses, such as domain names and URLs

New terms where they are defined

Program names, compilers, interpreters, utilities, and commands

Threads

Constant width is used for:

Anything that might appear in a Java program, including method names, variable names, and class names

Tags that might appear in an HTML or XML document

Keywords, objects, and environment variables

Constant width bold is used for:

Text that is typed by the user on the command line or in a dialog

Constant width italic is used for:

Replaceable items in code

In the main body of text, we always use a pair of empty parentheses after a method name to distinguish methods from variables and other creatures.

In the Java source listings, we follow the coding conventions most frequently used in the Java community. Class names begin with capital letters; variable and method names begin with lowercase. All the letters in the names of constants are capitalized. We don’t use underscores to separate words in a long name; following common practice, we capitalize individual words (after the first) and run the words together. For example: thisIsAVariable, thisIsAMethod(), ThisIsAClass, and THIS_IS_A_CONSTANT. Also, note that we differentiate between static and nonstatic methods when we refer to them. Unlike some books, we never write Foo.bar() to mean the bar() method of Foo unless bar() is a static method (paralleling the Java syntax in that case).

Index

Learning Java Index

About the Authors

Marc Loy caught the Java bug after seeing a beta copy of the HotJava browser showing a sorting algorithm animation back in 1994. He developed and delivered Java training classes at Sun Microsystems back in the day and has continued training a (much) wider audience ever since. He now spends his days consulting and writing on technical and media topics. He has also caught the maker bug and is exploring the fast-growing world of embedded electronics and wearables.

Patrick Niemeyer became involved with Oak (Java’s predecessor) while working at Southwestern Bell Technology Resources. He is the CTO of Ikayzo, Inc., and an independent consultant and author. Pat is the creator of BeanShell, a popular Java scripting language. He has served as a member of several JCP expert groups that guided features of the Java language and is a contributor to many open source projects. Most recently, Pat has been developing analytics software for the financial industry as well as advanced mobile applications. He currently lives in St. Louis with his family and various creatures.

Dan Leuck is the CEO of Ikayzo, Inc., a Tokyo- and Honolulu-based interactive design and software development firm with customers that include Sony, Oracle, Nomura, PIMCO, and the federal government. He previously served as Senior Vice President of Research and Development for Tokyo-based ValueCommerce, Asia’s largest online marketing company; Global Head of Development for London-based LastMinute.com, Europe’s largest B2C website; and President of the US division of DML. Dan has extensive experience managing teams of 150-plus developers in five countries. He has served on numerous advisory boards and panels for companies such as Macromedia and Sun Microsystems. Dan is active in the Java community, is a contributor to BeanShell and the project lead for SDL, and sits on numerous Java Community Process expert groups.

Colophon

The animals on the cover of Learning Java, Fifth Edition are a Bengal tiger and her cubs. The Bengal is a subsepecies of tiger (Panthera tigris tigris) found in Southern Asia. It has been hunted practically to extinction and now lives mostly in natural preserves and national parks, where it is strictly protected. It’s estimated that there are fewer than 3,500 Bengal tigers left in the wild.

The Bengal tiger is reddish orange with narrow black, gray, or brown stripes, generally in a vertical direction. Males can grow to nine feet long and weigh as much as 500 pounds; they are the largest existing members of the cat family. Preferred habitats include dense thickets, long grass, or tamarisk shrubs along river banks. Maximum longevity can be 26 years but is usually only about 15 years in the wild.

Tigers most commonly conceive after the monsoon rains; the majority of cubs are born between February and May after a gestation of three and a half months. Females bear one litter every two to three years. Cubs weigh under three pounds at birth and are striped. Litters usually consist of one to four cubs, but it’s unusual for more than two or three to survive. Cubs are weaned at four to six months but depend on their mother for food and protection for another two years. Female tigers are mature at three to four years, males at four to five years.

Bengals are an endangered species threatened by poaching, habitat loss, and habitat fragmentation. Many of the animals on O’Reilly covers are endangered; all of them are important to the world.

The color illustration is by Karen Montgomery, based on a black and white engraving from a loose plate, source unknown. The cover fonts are Gilroy Semibold and Guardian Sans. The text font is Adobe Minion Pro; the heading font is Adobe Myriad Condensed; and the code font is Dalton Maag’s Ubuntu Mono.

Fair Use Source: B086L2NYWR (LrnJav] 2023)