code: public static String buildCommaDelimitedList(Collection collection) {
          if (isNullOrEmpty(collection)) {
              return null;
          }
          StringBuilder sb = new StringBuilder();
          for (Object o : collection) {
              sb.append(o.toString().trim()).append(',');
          }
          sb.deleteCharAt(sb.length() - 1);
          return sb.toString();
      }
docs: Convert a collection into a comma delimited String.
  <br>
  Each object in the collection will be converted to a trimmed String, and commas will be used to
  separate each object.
  
  @param collection collection to convert.
  @return comma delimited string, or null if the collection is null or empty.