code: public List<String> getExcerptFieldNames() {
  
          if (m_excerptFieldNames == null) {
              // lazy initialize the field names
              m_excerptFieldNames = new ArrayList<String>();
              Iterator<CmsSearchField> i = getFields().iterator();
              while (i.hasNext()) {
                  CmsLuceneField field = (CmsLuceneField)i.next();
                  if (field.isInExcerptAndStored()) {
                      m_excerptFieldNames.add(field.getName());
                  }
              }
          }
  
          // create a copy of the list to prevent changes in other classes
          return new ArrayList<String>(m_excerptFieldNames);
      }
docs: Returns a list of all field names (Strings) that are used in generating the search excerpt.<p>
  
  @return a list of all field names (Strings) that are used in generating the search excerpt