src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> retry(Predicate<? super Throwable> predicate) {
        return retry(Long.MAX_VALUE, predicate);
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> retry(Predicate<? super Throwable> predicate) {
        return retry(Long.MAX_VALUE, predicate);
    }
Retries the current Observable if the predicate returns true.
<p>
<img width="640" height="248" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/retry.o.e.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code retry} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param predicate the predicate that receives the failure Throwable and should return true to trigger a retry.
@return the new Observable instance