code: public static <T extends Map.Entry<String, String>> Map<String, String> toMap(Collection<T> from) {
          HashMap<String, String> map = new HashMap<String, String>();
          if (from != null) {
              for (Map.Entry<String, String> entry : from) {
                  String key = entry.getKey();
                  if (!map.containsKey(key)) {
                      map.put(key, entry.getValue());
                  }
              }
          }
          return map;
      }
docs: Construct a Map containing a copy of the given parameters. If several
  parameters have the same name, the Map will contain the first value,
  only.