src/main/java/io/reactivex/Observable.java
@SuppressWarnings({ "unchecked", "rawtypes" })
    @CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Observable<T> mergeArray(int maxConcurrency, int bufferSize, ObservableSource<? extends T>... sources) {
        return fromArray(sources).flatMap((Function)Functions.identity(), false, maxConcurrency, bufferSize);
    }
@SuppressWarnings({ "unchecked", "rawtypes" })
    @CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Observable<T> mergeArray(int maxConcurrency, int bufferSize, ObservableSource<? extends T>... sources) {
        return fromArray(sources).flatMap((Function)Functions.identity(), false, maxConcurrency, bufferSize);
    }
Flattens an Iterable of ObservableSources into one ObservableSource, without any transformation, while limiting the
number of concurrent subscriptions to these ObservableSources.
<p>
<img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/merge.png" alt="">
<p>
You can combine the items emitted by multiple ObservableSources so that they appear as a single ObservableSource, by
using the {@code merge} method.
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code mergeArray} does not operate by default on a particular {@link Scheduler}.</dd>
<dt><b>Error handling:</b></dt>
<dd>If any of the source {@code ObservableSource}s signal a {@code Throwable} via {@code onError}, the resulting
{@code Observable} terminates with that {@code Throwable} and all other source {@code ObservableSource}s are disposed.
If more than one {@code ObservableSource} signals an error, the resulting {@code Observable} may terminate with the
first one's error or, depending on the concurrency of the sources, may terminate with a
{@code CompositeException} containing two or more of the various error signals.
{@code Throwable}s that didn't make into the composite will be sent (individually) to the global error handler via
{@link RxJavaPlugins#onError(Throwable)} method as {@code UndeliverableException} errors. Similarly, {@code Throwable}s
signaled by source(s) after the returned {@code Observable} has been disposed or terminated with a
(composite) error will be sent to the same global error handler.
Use {@link #mergeArrayDelayError(int, int, ObservableSource...)} to merge sources and terminate only when all source {@code ObservableSource}s
have completed or failed with an error.
</dd>
</dl>

@param <T> the common element base type
@param sources
the array of ObservableSources
@param maxConcurrency
the maximum number of ObservableSources that may be subscribed to concurrently
@param bufferSize
the number of items to prefetch from each inner ObservableSource
@return an Observable that emits items that are the result of flattening the items emitted by the
ObservableSources in the Iterable
@throws IllegalArgumentException
if {@code maxConcurrent} is less than or equal to 0
@see <a href="http://reactivex.io/documentation/operators/merge.html">ReactiveX operators documentation: Merge</a>
@see #mergeArrayDelayError(int, int, ObservableSource...)