Java SE 8 for the Really Impatient (2014)

Preface

This book gives a concise introduction to the many new features of Java 8 (and a few features of Java 7 that haven’t received much attention) for programmers who are already familiar with Java.

This book is written in the “impatient” style that I first tried out in a book called Scala for the Impatient. In that book, I wanted to quickly cut to the chase without lecturing the reader about the superiority of one paradigm over another. I presented information in small chunks organized to help you quickly retrieve it when needed. The approach was a big success in the Scala community, and I am employing it again in this book.

With Java 8, the Java programming language and library receive a major refresh. Lambda expressions make it possible to write “snippets of computations” in a concise way, so that you can pass them to other code. The recipient can choose to execute your computation when appropriate and as often as appropriate. This has a profound impact on building libraries.

In particular, working with collections has completely changed. Instead of specifying how to compute a result (“traverse from the beginning to the end, and if an element matches a condition, compute a value from it, and add that value to a sum”), you specify what you want (“give me the sum of all elements that match a condition”). The library is then able to reorder the computation—for example, to take advantage of parallelism. Or, if you just want to have the first hundred matches, it can stop the computation without you having to maintain a counter.

The brand-new stream API of Java 8 puts this idea to work. In the first chapter, you learn all about the syntax of lambda expressions, and Chapter 2 gives a complete overview of streams. In Chapter 3, I provide you with tips on how to effectively design your own libraries with lambdas.

With Java 8, developers of client-side applications need to transition to the JavaFX API since Swing is now in “maintenance mode.” Chapter 4 gives a quick introduction to JavaFX for a programmer who needs to put together a graphical program—when a picture speaks louder than 1,000 strings.

Having waited for far too many years, programmers are finally able to use a well-designed date/time library. Chapter 5 covers the java.time API in detail.

Each version of Java brings enhancements in the concurrency API, and Java 8 is no exception. In Chapter 6, you learn about improvements in atomic counters, concurrent hash maps, parallel array operations, and composable futures.

Java 8 bundles Nashorn, a high-quality JavaScript implementation. In Chapter 7, you will see how to execute JavaScript on the Java Virtual Machine, and how to interoperate with Java code.

Chapter 8 collects miscellaneous smaller, but nevertheless useful, features of Java 8. Chapter 9 does the same for Java 7, focusing on improved exception handling, the “new I/O” enhancements for working with files and directories, and other library enhancements that you may have missed.

My thanks go, as always, to my editor Greg Doench, who had the idea of a short book that brings experienced programmers up to speed with Java 8. Dmitry Kirsanov and Alina Kirsanova once again turned an XHTML manuscript into an attractive book with amazing speed and attention to detail. I am grateful to the reviewers who spotted many embarrassing errors and gave excellent suggestions for improvement. They are: Gail Anderson, Paul Anderson, James Denvir, Trisha Gee, Brian Goetz (special thanks for the very thorough review), Marty Hall, Angelika Langer, Mark Lawrence, Stuart Marks, Attila Szegedi, and Jim Weaver.

I hope that you enjoy reading this concise introduction to the new features of Java 8, and that it will make you a more successful Java programmer. If you find errors or have suggestions for improvement, please visit http://horstmann.com/java8 and leave a comment. On that page, you will also find a link to an archive file containing all code examples from the book.