RxJava

In our examples, we will use RxJava 2.2.21 (http://reactivex.io) . It can be added to the project using the following dependency:

<dependency>

    <groupId>io.reactivex.rxjava2</groupId>

    <artifactId>rxjava</artifactId>

    <version>2.2.21</version>

</dependency>

First, let’s compare two implementations of the same functionality using the java.util.stream package and the io.reactivex package. The sample program is going to be very simple:

• Create a stream of integers: 1, 2, 3, 4, and 5.
• Only filter the even numbers (that is, 2 and 4).
• Calculate the square root of each of the filtered numbers.
• Calculate the sum of all the square roots.

Here is how it can be implemented using the java.util.stream package (see the ObservableIntro class and the squareRootSum() method):

double a = IntStream.rangeClosed(1, 5)

 ...