Book Image

Mastering Concurrency Programming with Java 8

By : Javier Fernández González
Book Image

Mastering Concurrency Programming with Java 8

By: Javier Fernández González

Overview of this book

Concurrency programming allows several large tasks to be divided into smaller sub-tasks, which are further processed as individual tasks that run in parallel. All the sub-tasks are combined together once the required results are achieved; they are then merged to get the final output. The whole process is very complex. This process goes from the design of concurrent algorithms to the testing phase where concurrent applications need extra attention. Java includes a comprehensive API with a lot of ready-to-use components to implement powerful concurrency applications in an easy way, but with a high flexibility to adapt these components to your needs. The book starts with a full description of design principles of concurrent applications and how to parallelize a sequential algorithm. We'll show you how to use all the components of the Java Concurrency API from basics to the most advanced techniques to implement them in powerful concurrency applications in Java. You will be using real-world examples of complex algorithms related to machine learning, data mining, natural language processing, image processing in client / server environments. Next, you will learn how to use the most important components of the Java 8 Concurrency API: the Executor framework to execute multiple tasks in your applications, the phaser class to implement concurrent tasks divided into phases, and the Fork/Join framework to implement concurrent tasks that can be split into smaller problems (using the divide and conquer technique). Toward the end, we will cover the new inclusions in Java 8 API, the Map and Reduce model, and the Map and Collect model. The book will also teach you about the data structures and synchronization utilities to avoid data-race conditions and other critical problems. Finally, the book ends with a detailed description of the tools and techniques that you can use to test a Java concurrent application.
Table of Contents (18 chapters)
Mastering Concurrency Programming with Java 8
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

The second example – a recommendation system


A recommendation system recommends a product or a service to a customer based on the products/services he has bought/used and on the products/services bought/used by the users that have bought/used the same services as him.

We have used the example explained in the previous section to implement a recommendation system. Each description of a product includes the reviews of a number of customers to a product. This review includes the score the customer gives to the product.

In this example, you will use these reviews to get a list of the products that may be interesting to a customer. We will obtain the list of the products purchased by a customer. In order to get that list, a list of the users who have purchased those products and the list of products purchased by those users are sorted using the average score given in the reviews. That will be the suggested products for the user.

Common classes

We have added two new classes to the ones used in the...