Book Image

Design Patterns and Best Practices in Java

By : Kamalmeet Singh, Adrian Ianculescu, Lucian-Paul Torje
Book Image

Design Patterns and Best Practices in Java

By: Kamalmeet Singh, Adrian Ianculescu, Lucian-Paul Torje

Overview of this book

Having a knowledge of design patterns enables you, as a developer, to improve your code base, promote code reuse, and make the architecture more robust. As languages evolve, new features take time to fully understand before they are adopted en masse. The mission of this book is to ease the adoption of the latest trends and provide good practices for programmers. We focus on showing you the practical aspects of smarter coding in Java. We'll start off by going over object-oriented (OOP) and functional programming (FP) paradigms, moving on to describe the most frequently used design patterns in their classical format and explain how Java’s functional programming features are changing them. You will learn to enhance implementations by mixing OOP and FP, and finally get to know about the reactive programming model, where FP and OOP are used in conjunction with a view to writing better code. Gradually, the book will show you the latest trends in architecture, moving from MVC to microservices and serverless architecture. We will finish off by highlighting the new Java features and best practices. By the end of the book, you will be able to efficiently address common problems faced while developing applications and be comfortable working on scalable and maintainable projects of any size.
Table of Contents (15 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Creating Observables


The following operators are used to create Observables from scratch, out of existing objects, arrays of other data structure, or by a sequence or timer.

The create operator

Creating Observables from scratch can be done by calling one of the following io.reactivex.Observable methods (operators):

  • Create
  • Generate
  • UnsafeCreate

The following example shows how to construct an Observable from scratch. Call onNext() until the observer is not disposed, onComplete() and onError() programmatically in order to get a 1 to 4 range of numbers:

As we can see in the preceding screenshot, the output is as expected, range from 1 to 4, and the sequence gets disposed of after usage.

The defer operator

Creating a new Observable for each observer once the observer connects can be done by calling the defer method. The following code shows the usage of defer for the case when we supply a number:

The console print-line method outputs 123, which is the Observable-wrapped integer.

The empty operator

Creating...