elementAt()

You can get a specific emission by its index specified by a Long, starting at 0. After that item is found and emitted, onComplete() will be called and the subscription will be disposed of.

If you want to get the fourth emission coming from an Observable, you can do it as shown in the following code snippet:

import io.reactivex.Observable;

public class Launcher {
      public static void main(String[] args) {

        Observable.just("Alpha", "Beta", "Zeta", "Eta", "Gamma", 
"Delta")
            .elementAt(3)
            .subscribe(i -> System.out.println("RECEIVED: " + i));
      }
}

The output of the following code snippet is as follows:

RECEIVED: Eta

You may not have noticed, but elementAt() returns Maybe<T> instead of Observable<T>. This is because it will yield one emission, but if there are fewer emissions than the sought index, it will be empty.

There are other flavors of elementAt(), such as elementAtOrError(), which return a Single and will emit an error if an element at that index is not found. singleElement() will turn an Observable into a Maybe, but will produce an error if there is anything beyond one element. Finally, firstElement() and lastElement() will yield, maybe emitting the first or last emission, respectively.