code: private void storeList(Properties props, Map<String, List<String>> details,
              String field) {
          Set<String> valueSet = new LinkedHashSet<String>();
          // merge with original property value if exists
          String currentValue = props.getProperty(field, "");
          if (!"".equals(currentValue)) {
              String[] currentList = currentValue.split(",");
              valueSet.addAll(Arrays.asList(currentList));
          }
          valueSet.addAll(details.get(field));
          String joinedList = StringUtils.join(valueSet, ",");
          props.setProperty(field, joinedList);
      }
docs: Take a list of strings from a Java Map, concatenate the values together
  and store them in a Properties object using the Map's original key.
  
  @param props : Properties object to store into
  @param details : The full Java Map
  @param field : The key to use in both objects