code: public IHillSlope getUpstreamElementAtPfafstetter( PfafstetterNumber pNum ) {
          // am I the one
          if (pfafstetterNumber.compareTo(pNum) == 0) {
              return this;
          }
          // // perhaps my upstream elements
          // for( UpstreamElement upstreamElement : upstreamElements ) {
          // if (upstreamElement.getPfafstetterNumber().compare(
          // upstreamElement.getPfafstetterNumber(), pNum) == 0) {
          // return upstreamElement;
          // }
          // }
          // digg further
          IHillSlope theChosen = null;
          for( IHillSlope upstreamElement : upstreamElements ) {
              theChosen = upstreamElement.getUpstreamElementAtPfafstetter(pNum);
              if (theChosen != null) {
                  break;
              }
          }
          return theChosen;
      }
docs: /* (non-Javadoc)
  @see org.hortonmachine.hmachine.modules.hydrogeomorphology.adige.core.IHillSlope#getUpstreamElementAtPfafstetter(org.hortonmachine.hmachine.modules.network.PfafstetterNumber)