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

Summary


In this chapter, you learned the different mechanisms that you can use to work with tasks that return a result. These tasks are based on the Callable interface, which declares the call() method. This is a parameterized interface with the class returned by the call method.

When you execute a Callable task in an executor, you will always obtain an implementation of the Future interface. You can use this object to cancel the execution of the task, know if the task has finished its execution or get the result returned by the call() method.

You send Callable tasks to the executor using three different methods. With the submit() method, you send one task, and you will get immediately a Future object associated with this task. With the invokeAll() method, you send a list of tasks and will get a list of Future objects when all the tasks have finished its execution. With the invokeAny() method, you send a list of tasks, and you will receive the result (not a Future object) of the first task...