src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> doOnComplete(Action onComplete) {
        return doOnEach(Functions.emptyConsumer(), Functions.emptyConsumer(), onComplete, Functions.EMPTY_ACTION);
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> doOnComplete(Action onComplete) {
        return doOnEach(Functions.emptyConsumer(), Functions.emptyConsumer(), onComplete, Functions.EMPTY_ACTION);
    }
Modifies the source ObservableSource so that it invokes an action when it calls {@code onComplete}.
<p>
<img width="640" height="358" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/doOnComplete.o.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code doOnComplete} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param onComplete
the action to invoke when the source ObservableSource calls {@code onComplete}
@return the source ObservableSource with the side-effecting behavior applied
@see <a href="http://reactivex.io/documentation/operators/do.html">ReactiveX operators documentation: Do</a>