code: public final static <T extends Comparable<? super T>> Observable<T> max(Observable<T> source) {
          return OperatorMinMax.max(source);
      }
docs: Returns an Observable that emits the single item emitted by the source Observable with the maximum
  numeric value. If there is more than one item with the same maximum value, it emits the last-emitted of
  these.
  <p>
  <img width="640" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/max.png" alt="">
  
  @param source
  an Observable to scan for the maximum emitted item
  @return an Observable that emits this maximum item
  @throws IllegalArgumentException
  if the source is empty
  @see <a href="https://github.com/ReactiveX/RxJava/wiki/Mathematical-and-Aggregate-Operators#wiki-max">RxJava Wiki: max()</a>
  @see <a href="http://msdn.microsoft.com/en-us/library/hh211837.aspx">MSDN: Observable.Max</a>