code: public static List<String> normalizeTagsForSearch(List<String> list) {
          if (isNullOrEmpty(list)) {
              return null;
          }
          List<String> tmp = new ArrayList<String>();
          for (String s : list) {
              tmp.add(s.replaceAll("[!#$%&'()*+\\.,'; ]", "").toLowerCase());
          }
          return tmp;
      }
docs: Normalize a List of Flickr tags for search calls.
  <br>
  This method takes a list of tags and converts them to the normalized representation that Flickr uses (at least,
  as close to the normalized version as could be figured out).
  <br>
  Each String in the list will have the following characters removed: !#$%&amp;'() *+.,';
  The String is then converted to lowercase and added to a new List.
  <br>
  Normalization is done primarily so that tags containing spaces do not have to be surrounded with double quotes
  before sending to the Flickr API. It is easier to normalize than to surround everything with double quotes, and
  this also results is slightly smaller (and more readable) calls to the Flickr API.
  
  @param list Flickr tags to normalize.
  @return new List containing normalized tags.