Reactive programming with Spring Reactor

Reactor is a library that implements reactive programming concepts for the JVM. This approach is based on the Observer pattern, and it provides types that can emit zero, one, or a sequence of values.

In this section, you will learn the following:

• How to implement the Observer pattern
• How to use the Flux publisher
• How to use the Mono publisher

The Observer pattern

The Observer pattern assumes that there is an object that sends a message, and another object that receives it. The following diagram shows how a class hierarchy can be organized to implement this approach:

The Activity class implements the OnClickListener interface and contains an instance of the Button class, while the...