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Learning Java Functional Programming

You're reading from   Learning Java Functional Programming Create robust and maintainable Java applications using the functional style of programming

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Product type Paperback
Published in Oct 2015
Publisher
ISBN-13 9781783558483
Length 296 pages
Edition 1st Edition
Languages
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Authors (2):
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Richard M. Reese Richard M. Reese
Author Profile Icon Richard M. Reese
Richard M. Reese
Richard M Reese Richard M Reese
Author Profile Icon Richard M Reese
Richard M Reese
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Table of Contents (11) Chapters Close

Preface 1. Getting Started with Functional Programming 2. Putting the Function in Functional Programming FREE CHAPTER 3. Function Composition and Fluent Interfaces 4. Streams and the Evaluation of Expressions 5. Recursion Techniques in Java 8 6. Optional and Monads 7. Supporting Design Patterns Using Functional Programming 8. Refactoring, Debugging, and Testing 9. Bringing It All Together Index

The Stream class and its use

The Stream class provides the primary support for the stream concept in Java. However, there are specialized classes, such as the DoubleStream, IntStream, and LongStream classes, that handle numbers. In addition, the Collection interface supports the creation of streams.

A stream will support either a finite or an infinite sequence of elements. The methods of a stream can be classified in a number of ways such as mapping, filtering, and sorting type methods. We will start with a simple example of a stream, and then follow up with a discussion of how they are created and several of their methods.

Let's assume that we need to process an array of numbers by summing the values of each unique element. For example, in the following array, there are six distinct numbers whose sum is 35:

    int[] numbers = {3,6,8,8,4,6,3,3,5,6,9,4,3,6};

One approach to solve the problem involves:

  1. Finding the distinct numbers in the array.
  2. Summing these numbers.

Finding the distinct...

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