@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<T> onErrorReturnItem(final T item) {
        ObjectHelper.requireNonNull(item, "item is null");
        return onErrorReturn(Functions.justFunction(item));
    }
@ CheckReturnValue @ BackpressureSupport ( BackpressureKind . FULL ) @ SchedulerSupport ( SchedulerSupport . NONE ) public final Flowable < T > onErrorReturnItem ( final T item ) { ObjectHelper . requireNonNull ( item , "item is null" ) ; return onErrorReturn ( Functions . justFunction ( item ) ) ; }
Instructs a Publisher to emit an item (returned by a specified function) rather than invoking
{@link Subscriber#onError onError} if it encounters an error.
<p>
<img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/onErrorReturn.png" alt="">
<p>
By default, when a Publisher encounters an error that prevents it from emitting the expected item to
its {@link Subscriber}, the Publisher invokes its Subscriber's {@code onError} method, and then quits
without invoking any more of its Subscriber's methods. The {@code onErrorReturn} method changes this
behavior. If you pass a function ({@code resumeFunction}) to a Publisher's {@code onErrorReturn}
method, if the original Publisher encounters an error, instead of invoking its Subscriber's
{@code onError} method, it will instead emit the return value of {@code resumeFunction}.
<p>
You can use this to prevent errors from propagating or to supply fallback data should errors be
encountered.
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure from downstream. The source {@code Publisher}s is expected to honor
backpressure as well. If it this expectation is violated, the operator <em>may</em> throw
{@code IllegalStateException} when the source {@code Publisher} completes or
{@code MissingBackpressureException} is signaled somewhere downstream.</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code onErrorReturnItem} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param item
the value that is emitted along with a regular onComplete in case the current
Flowable signals an exception
@return the original Publisher with appropriately modified behavior
@see <a href="http://reactivex.io/documentation/operators/catch.html">ReactiveX operators documentation: Catch</a>