Book Image

Java 9 Concurrency Cookbook, Second Edition - Second Edition

By : Javier Fernández González
Book Image

Java 9 Concurrency Cookbook, Second Edition - Second Edition

By: Javier Fernández González

Overview of this book

Writing concurrent and parallel programming applications is an integral skill for any Java programmer. Java 9 comes with a host of fantastic features, including significant performance improvements and new APIs. This book will take you through all the new APIs, showing you how to build parallel and multi-threaded applications. The book covers all the elements of the Java Concurrency API, with essential recipes that will help you take advantage of the exciting new capabilities. You will learn how to use parallel and reactive streams to process massive data sets. Next, you will move on to create streams and use all their intermediate and terminal operations to process big collections of data in a parallel and functional way. Further, you’ll discover a whole range of recipes for almost everything, such as thread management, synchronization, executors, parallel and reactive streams, and many more. At the end of the book, you will learn how to obtain information about the status of some of the most useful components of the Java Concurrency API and how to test concurrent applications using different tools.
Table of Contents (12 chapters)

Reducing the elements of a stream

MapReduce is a programming model used to process very large datasets in distributed environments using a lot of machines working in a cluster. This programming model has the following two operations:

  • Map: This operation filters and transforms the original elements into a form more suitable to the reduction operation
  • Reduce: This operation generates a summary result from all the elements, for example, the sum or the average of numeric values

This programming model has been commonly used in the functional programming world. In the Java ecosystem, the Hadoop project of the Apache Software Foundation provides an implementation of this model. The Stream class implements two different reduce operations:

  • The pure reduce operation, implemented in the different versions of the reduce() method that process a stream of elements to obtain a value
  • The mutable reduction implemented in the...