How to use RxJava to process multiple threads in parallel & in sequence

 Hi,

In this blog I will discuss 2 scenarios where RxJava threading can be helpful:

1. Run Multiple threads in parallel & wait for all of them to complete

2. Run threads sequentially (one after another)

First, add the below dependency in Maven

<dependency>
    <groupId>io.reactivex.rxjava2</groupId>
    <artifactId>rxjava</artifactId>
    <version>2.2.21</version>
</dependency>

Below are the 2 Completable threads created

import io.reactivex.Completable;
import io.reactivex.schedulers.Schedulers;

Completable cp1= Completable.fromAction(()->{
     //business logic
}).subscribeOn(Schedulers.io());

Completable cp2= Completable.fromAction(()->{
   //business logic
}).subscribeOn(Schedulers.io());
Now for scenario 1
cp1.mergeWith(cp2).blockingAwait(); // cp1 & cp2 will run concurrently & wait for complete for both tasks

For scenario 2
cp1.andThen(cp2).subscribe(); //cp2 will run after cp1
Further Reading:
https://solidsoft.wordpress.com/2016/02/26/parallel-execution-of-blocking-tasks-with-rxjava-and-completable/