Hello Reactive programming with RxJava2

RxJava2 is the library for Reactive programming in Java. Let’s get started with a very simple piece of code.
In Reactive Programming, we have a publisher and a subscriber. Publisher publishes(or Pushes) data to a subscriber. When the subscriber receives data, it Reacts.

Include the RxJava2 library. The pom.xml is shown below. We need Java 8 and above.

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.healthycoder</groupId>
    <artifactId>Reactive_Java</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>io.reactivex.rxjava2</groupId>
            <artifactId>rxjava</artifactId>
            <version>2.1.4</version>
        </dependency>

    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

We’ll create a class HelloWorld and create a publisher and subscriber as shown below.

package com.healthycoder;

import io.reactivex.Observable;

public class HelloWorld {
    public static void main(String[] args) throws Exception{
        Observable<String> producer = Observable.just("Hello World"); 
        producer.subscribe(System.out::println); 
    }
}

Yes!!! You’re right. We are implementing Observer Pattern here. Reactive programming to begin with is termed as “Observer pattern done right”. We have created an Observable stream that pushes strings. We have a subscriber who just prints it!!!
Alright we have taken the first step into reactive world. Let’s take baby steps. One piece at a time