Java 8 Lambdas

Preface

For years, functional programming has been considered the realm of a small band of specialists who consistently claimed superiority to the masses while being unable to spread the wisdom of their approach. The main reason I’ve written this book is to challenge both the idea that there’s an innate superiority in the functional style and the belief that its approach should be relegated to a small band of specialists!

For the last two years in the London Java Community, I’ve been getting developers to try out Java 8 in some form or another. I’ve found that many of our members enjoy the new idioms and libraries that it makes available to them. They may reel at the terminology and elitism, but they love the benefits that a bit of simple functional programming provides to them. A common thread is how much easier it is to read code using the new Streams API to manipulate objects and collections, such as filtering out albums that were made in the UK from a List of all albums.

What I’ve learned when running these kinds of events is that examples matter. People learn by repeatedly digesting simple examples and developing an understanding of patterns out of them. I’ve also noticed that terminology can be very off-putting, so anytime there’s a hard-sounding concept, I give an easy-to-read explanation.

For many people, what Java 8 offers by way of functional programming is incredibly limited: no monads,^[1] no language-level lazy evaluation, no additional support for immutability. As pragmatic ...