Java 8 Lambdas in Action is a clearly-written guide to Java 8 lambdas and functional programming in Java. It begins with a practical introduction to the structure and benefits of lambda expressions in real-world Java code. The book then introduces the Stream API and shows how it can make collections-related code radically easier to understand and maintain. Along the way, you'll discover new FP-oriented design patterns with Java 8 for code reuse, code readability, exception handling, data manipulation, and concurrency. For developers also exploring other functional languages on the JVM, the book concludes with a quick survey of useful functional features in Scala and Clojure.

★★☆☆☆

To be short: It's a good book, but it is extremely (and unnecessary) verbose.

It covers the new stuff on Java 8 (like streams and lambdas) and some of Java 9 (like the Flow/reactive interface). It does a good job on Streams and Lambdas, but seems to fall a bit short on the reactive interface, maybe 'cause it's just an interface, although I found the examples a little bit missing in some points, like showing the Three interfaces, Subscriber, Subscription and Publisher, but showing examples without the Publisher. A bit worse (IMHO), is that, in order to produce an example, instead of publishing some data, it shows a generic publisher of sequential numbers, in which it calls the real publisher.

Also, the authors seem a bit too enthusiastic about lambdas. Even when the code becomes less readable -- specially in the Flow examples -- they still use lambdas. They are so into it that the example of a for being converted to a stream is shown at least 4 times.

There are too many "as follows"; there are too many "in the next section" just before the next section; there is too much repetition that shouldn't be there.

Again, the content is good, but the text is terrible.