src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Flowable<T> concatArray(Publisher<? extends T>... sources) {
        if (sources.length == 0) {
            return empty();
        } else
        if (sources.length == 1) {
            return fromPublisher(sources[0]);
        }
        return RxJavaPlugins.onAssembly(new FlowableConcatArray<T>(sources, false));
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Flowable<T> concatArray(Publisher<? extends T>... sources) {
        if (sources.length == 0) {
            return empty();
        } else
        if (sources.length == 1) {
            return fromPublisher(sources[0]);
        }
        return RxJavaPlugins.onAssembly(new FlowableConcatArray<T>(sources, false));
    }
Concatenates a variable number of Publisher sources.
<p>
Note: named this way because of overload conflict with concat(Publisher&lt;Publisher&gt;).
<p>
<img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/concat.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure from downstream. The {@code Publisher}
sources are expected to honor backpressure as well.
If any of the source {@code Publisher}s violate this, it <em>may</em> throw an
{@code IllegalStateException} when the source {@code Publisher} completes.</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code concatArray} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
@param sources the array of sources
@param <T> the common base value type
@return the new Publisher instance
@throws NullPointerException if sources is null