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

Implementing the command pattern


The command pattern is useful for storing an arbitrary set of operations that can be executed at a later time. It has been used to support GUI action controls such as buttons and menus, recording macros, and supporting undo operations.

It is a behavioral design pattern where an object encapsulates the information needed to perform an operation at a later time. We will illustrate this pattern using a macro-like facility where a character can walk, run, or jump. A sequence of these actions can be saved and executed as needed.

Object-oriented solution to the command pattern

We start with the declaration of the Command interface as shown next. It has a single method, execute, whose intent is to execute some command and return whether it was successful or not.

public interface Command {
   public boolean execute();
}

The Move interface details the actions that will be supported:

public interface Move {
   public boolean walk();
   public boolean run();
   public boolean...