private void listToLowerCase(List<String> list) {
    if (list == null) {
      return;
    }
    for (int i = 0; i < list.size(); i++) {
      list.set(i, list.get(i).toLowerCase());
    }
  }
Convert the elements of a list to lowercase.
@param list
ambari-server/src/main/java/org/apache/ambari/server/configuration/Configuration.java