Book Image

Learning Concurrent Programming in Scala - Second Edition

By : Aleksandar Prokopec
Book Image

Learning Concurrent Programming in Scala - Second Edition

By: Aleksandar Prokopec

Overview of this book

Scala is a modern, multiparadigm programming language designed to express common programming patterns in a concise, elegant, and type-safe way. Scala smoothly integrates the features of object-oriented and functional languages. In this second edition, you will find updated coverage of the Scala 2.12 platform. The Scala 2.12 series targets Java 8 and requires it for execution. The book starts by introducing you to the foundations of concurrent programming on the JVM, outlining the basics of the Java Memory Model, and then shows some of the classic building blocks of concurrency, such as the atomic variables, thread pools, and concurrent data structures, along with the caveats of traditional concurrency. The book then walks you through different high-level concurrency abstractions, each tailored toward a specific class of programming tasks, while touching on the latest advancements of async programming capabilities of Scala. It also covers some useful patterns and idioms to use with the techniques described. Finally, the book presents an overview of when to use which concurrency library and demonstrates how they all work together, and then presents new exciting approaches to building concurrent and distributed systems. Who this book is written for If you are a Scala programmer with no prior knowledge of concurrent programming, or seeking to broaden your existing knowledge about concurrency, this book is for you. Basic knowledge of the Scala programming language will be helpful.
Table of Contents (19 chapters)
Learning Concurrent Programming in Scala - Second Edition
About the Author
About the Reviewers
Customer Feedback

Composing Observable objects

Having seen different ways of creating various types of the Observable objects, subscribing to their events, and using the Subscription objects, we turn our attention to composing the Observable objects into larger programs. From what we have seen so far, the advantages of using the Observable objects over a callback-based API are hardly worth the trouble.

The true power of Rx becomes apparent when we start composing the Observable objects using various combinators. We can think of an Observable object in a similar way as we think of Scala sequence collections. In a Scala sequence, represented by the Seq[T] trait, elements of type T are ordered in the memory according to their indices. In an Observable[T] trait, events of type T are ordered in time.

Let's use the Observable.interval factory method in order to create an Observable object, which asynchronously emits a number every 0.5 seconds, and then output the first five odd numbers. To do this, we first call...