@Override public void next(){
  currentImage=Optional.of(addIndexAndGetImageByOffset(+1));
  eventBus.post(new SourceHasPendingUpdateEvent(this));
}

@ Override public void next ( ) { currentImage = Optional . of ( addIndexAndGetImageByOffset ( + 1 ) ) ; eventBus . post ( new SourceHasPendingUpdateEvent ( this ) ) ; }
assigns the output socket to the next image . ( wraps around )
