code: @Override
      public void removeMapping(int pos) {
          for (int i = pos; i < mappingCount - 1; i++) {
              map[i] = map[i + 1];
          }
          map[mappingCount - 1] = null;
          mappingCount--;
          notifyChanged();
      }
docs: Removes a mapping between the reactant and product side to this
  Reaction.
  
  @param  pos  Position of the Mapping to remove.
  @see   #mappings