src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<T> mergeWith(Publisher<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return merge(this, other);
    }
@CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<T> mergeWith(Publisher<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return merge(this, other);
    }
Flattens this and another Publisher into a single Publisher, without any transformation.
<p>
<img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/merge.png" alt="">
<p>
You can combine items emitted by multiple Publishers so that they appear as a single Publisher, by
using the {@code mergeWith} method.
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure from downstream. This and the other {@code Publisher}s are expected to honor
backpressure; if violated, the operator <em>may</em> signal {@code MissingBackpressureException}.</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code mergeWith} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param other
a Publisher to be merged
@return a Flowable that emits all of the items emitted by the source Publishers
@see <a href="http://reactivex.io/documentation/operators/merge.html">ReactiveX operators documentation: Merge</a>