src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<T> sorted() {
        return toList().toFlowable().map(Functions.listSorter(Functions.<T>naturalComparator())).flatMapIterable(Functions.<List<T>>identity());
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<T> sorted() {
        return toList().toFlowable().map(Functions.listSorter(Functions.<T>naturalComparator())).flatMapIterable(Functions.<List<T>>identity());
    }
Returns a Flowable that emits the events emitted by source Publisher, in a
sorted order. Each item emitted by the Publisher must implement {@link Comparable} with respect to all
other items in the sequence.

<p>If any item emitted by this Flowable does not implement {@link Comparable} with respect to
all other items emitted by this Flowable, no items will be emitted and the
sequence is terminated with a {@link ClassCastException}.
<p>Note that calling {@code sorted} with long, non-terminating or infinite sources
might cause {@link OutOfMemoryError}

<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure from downstream and consumes the source {@code Publisher} in an
unbounded manner (i.e., without applying backpressure to it).</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code sorted} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@return a Flowable that emits the items emitted by the source Publisher in sorted order