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
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Monitors and synchronization

In this section, we will study inter-thread communication using the synchronized statement in more detail. As we saw in the previous sections, the synchronized statement serves both to ensure the visibility of writes performed by different threads, and to limit concurrent access to a shared region of memory. Generally speaking, a synchronization mechanism that enforces access limits on a shared resource is called a lock. Locks are also used to ensure that no two threads execute the same code simultaneously; that is, they implement mutual exclusion.

As mentioned previously, each object on the JVM has a special built-in monitor lock, also called the intrinsic lock. When a thread calls the synchronized statement on an x object, it gains ownership of the monitor lock of the x object, given that no other thread owns the monitor. Otherwise, the thread is blocked until the monitor is released. Upon gaining ownership of the monitor, the thread can witness the memory writes...