Java 8 in Action
Lambdas, streams, and functional-style programming
Raoul-Gabriel Urma, Mario Fusco, Alan Mycroft
(Manning – paperback)
Java 8, we were sometimes assured, would just be Java 7 with a few slick new (or past-due) features added.
Actually, now that it’s here, Java 8 represents “the biggest change to Java in the 18 years since Java 1.0 was released,” the three authors of this fine new book point out.
Of course, news of “big changes” seldom sits well with developers who have spent countless hours learning and getting comfortable with one particular version of a programming language.
And many coders and companies will continue sticking with Java 7 for a while longer, because it still works. But the adoption pace for Java 8 keeps picking up. So, to misquote an old sci-fi slogan, resistance soon will become somewhat futile.
Lambdas, streams, and functional-style programming capabilities are Java 8’s headline additions. And there are some other major and minor additions, as well, including default methods and a new Date and Time API.
Java 8 in Action does an excellent job of introducing these new capabilities, and the book offers many short code examples and other illustrations to show how to put the new Java 8 capabilities to work.
Indeed, short (and shorter!) code is one of the hallmarks of Java 8. “In Java 8 you can write more concise code that reads a lot closer to the problem statement,” the writers emphasize. To illustrate that point, they offer a five-line example of verbose Java 7 code and follow it with a one-line Java 8 code example that accomplishes the same thing. Other examples also drive home the coding efficiencies that Java 8 can offer.
Lambdas, also known as anonymous functions, enable you to skip writing method definitions that will only be used once. The authors note that “passing code is currently tedious and verbose in Java [meaning 7 and earlier]. Well, good news! Lambdas fix this problem: they let you pass code in a concise way. Lambdas technically don’t let you do anything you couldn’t do prior to Java 8. But you no longer have to write clumsy code using anonymous classes to benefit from behavior parameterization!”
The new Streams API makes it much easier to work with collections in Java and provides “a much different way to process data in comparison to the Collections API.” Using the Streams API, “you don’t need to think in terms of loops at all. The data processing happens internally inside the library.”
Meanwhile, if you are a diehard object-oriented programmer, you may be leery of the term “functional programming” and the notion of using functions as values. (“In practice, you can’t completely program in pure functional style in Java,” the authors note. Instead, you will learn how to write “functional-style programs” in which you hide the side effects.)
With Java 8, “two core ideas from functional programming…are now part of Java: using methods and lambdas as first-class values, and the idea that calls to functions or methods can be efficiently and safely executed in parallel in the absence of mutable shared state. Both of these ideas are exploited by the new Streams API,” the writers state. Also, in Java 8, they add, “there’s an Optional class that, if used consistently can help you avoid NullPointer exceptions.”
This review barely dents the surface of this excellent how-to book’s contents. Whether you are learning Java now or you are a Java developer who wants to keep your coding skills up-to-date and sharp, Java 8 in Action should be a book you will read soon.