src/main/java/io/reactivex/Single.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Single<T> cache() {
        return RxJavaPlugins.onAssembly(new SingleCache<T>(this));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Single<T> cache() {
        return RxJavaPlugins.onAssembly(new SingleCache<T>(this));
    }
Stores the success value or exception from the current Single and replays it to late SingleObservers.
<p>
The returned Single subscribes to the current Single when the first SingleObserver subscribes.
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code cache} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@return the new Single instance
@since 2.0