Book Image

Learning Java Functional Programming

By : Richard M Reese, Richard M. Reese
Book Image

Learning Java Functional Programming

By: Richard M Reese, Richard M. Reese

Overview of this book

Functional programming is an increasingly popular technology that allows you to simplify many tasks that are often cumbersome and awkward using an object-oriented approach. It is important to understand this approach and know how and when to apply it. Functional programming requires a different mindset, but once mastered it can be very rewarding. This book simplifies the learning process as a problem is described followed by its implementation using an object-oriented approach and then a solution is provided using appropriate functional programming techniques. Writing succinct and maintainable code is facilitated by many functional programming techniques including lambda expressions and streams. In this book, you will see numerous examples of how these techniques can be applied starting with an introduction to lambda expressions. Next, you will see how they can replace older approaches and be combined to achieve surprisingly elegant solutions to problems. This is followed by the investigation of related concepts such as the Optional class and monads, which offer an additional approach to handle problems. Design patterns have been instrumental in solving common problems. You will learn how these are enhanced with functional techniques. To transition from an object-oriented approach to a functional one, it is useful to have IDE support. IDE tools to refactor, debug, and test functional programs are demonstrated through the chapters. The end of the book brings together many of these functional programming techniques to create a more comprehensive application. You will find this book a very useful resource to learn and apply functional programming techniques in Java.
Table of Contents (16 chapters)
Learning Java Functional Programming
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Lazy and eager evaluation


There are three terms dealing with this topic: lazy loading, lazy evaluation, and eager evaluation. They are all present in most functional programming languages. These terms are defined as follows:

  • Lazy loading: Delaying an expensive loading operation until needed.

  • Lazy evaluation: Refers to the delaying of the evaluation of an operation until it is needed. Lazy evaluation support infinite streams.

  • Eager evaluation: An operation is executed as soon as it is encountered.

We will discuss lazy and eager evaluation in this section. Lazy loading can occur when a line of a file is not read until it needs to be processed. This can occur in a stream when a line is read depending on the operations performed. Streams are sometimes called lazy sequences because they are often evaluated in a lazy manner.

The following demonstrates lazy evaluation. A part of this example first appeared in Chapter 1, Getting Started with Functional Programming. Here, we clearly show that the stream...