Learning RxJava

contains()

The contains() operator will check whether a specific element (based on the hashCode()/equals() implementation) ever emits from an Observable. It will return a Single<Boolean> that will emit true if it is found and false if it is not.

In the following code snippet, we emit the integers 1 through 10000, and we check whether the number 9563 is emitted from it using contains():

import io.reactivex.Observable;public class Launcher {      public static void main(String[] args) {        Observable.range(1,10000)          .contains(9563)          .subscribe(s -> System.out.println("Received: " + s));      }}

The output of the preceding code snippet is as follows:

    Received: true

As you can probably guess, the moment the element is found, it will emit true and call onComplete() ...