RxJava 2.x with Room and Retrofit 2.x with MVP pattern

What is RxJava?

RxJava is an art and endless possibilities await those who can master it.

RxJava is a Java VM implementation of Reactive Extensions.

From the official doc, Reactive Extensions(ReactiveX) is as a library for composing asynchronous and event-based programs by using observable sequences.

Now we have to learn these three terms - asynchronous, event-based and observable sequences.

Asynchronous: Different parts of the program run simultaneously.

Event-Based: The program executes the code based on the event generated.

Flowable and Observable

RxJava provides more types of event publishers:

• Flowable Publisher that emits 0..N elements, and then completes successfully or with an error

• Observable like Flowables but without a backpressure strategy. They were introduced in RxJava 1.x

• Single a specialized emitter that completes with a value successfully either an error.(doesn't have onComplete callback, instead onSuccess(val))

• Maybe a specialized emitter that can complete with / without a value or complete with an error.

• Completable a specialized emitter that just signals if it completed successfully or with an error.

I found this link very worthy to understand Observable and its Subscriber's builtin methods.

IMPORTANT

Observable and Flowable can emit multiple items

Single, Maybe and Completable are one or no emission of items.

Flowable Backpressure Strategy

• Buffer
• Drop
• Latest
• Error
• Missing

Simple Operators

• delay
• interval
• scan
• reduce
• collect

Other components are as follows:

• Subscription - work is going on or completed or is used to cancel.
• Operators - Modify Data
• Schedulers - Where the work should be done, which thread like main thread, etc.
• Subscriber/Disposable - where the response will be sent after work has been completed.

Understanding RxJava Subject

What is Subject?

A Subject is a sort of bridge or proxy that is available in some implementations of ReactiveX that acts both as an observer and as an Observable. Because it is an observer, it can subscribe to one or more Observables, and because it is an Observable, it can pass through the items it observes by re-emitting them, and it can also emit new items.

detailed explanation here

RxJava2 with MVP structure

This is the diagram of how we can use Rxjava on MVP structure.

please see ui and data package

This explanation is taken from google's Rx example with MVP link

RxJava2 with Room

The following link contains a details explanation of how Rxjava can be used on Room persistence library

to get the demo code go to manifest file and run 
AddTaskActivity.java

RxJava2 with Retrofit2

The following link contains a details explanation of why Rxjava is best solution for REST Api related task.

  to get the demo code go to manifest file and run 
  GetRemoteCouponActivity.java