code: public void diff(DiffHandler handler, DiffCriteria criteria)
          throws DiffException
      {
          diff(handler, criteria, oldVersion, newVersion, oldClassInfo, newClassInfo);
      }
docs: Perform a diff sending the output to the specified handler, using
  the specified criteria to select diffs.
  
  @param handler The handler to receive and handle differences.
  @param criteria The criteria we use to select differences.
  @throws DiffException when there is an underlying exception, e.g.
  writing to a file caused an IOException