please include function getOpt_cached.

static HashMap<S, Field> instanceFieldsMap(O o) {
  Class c = o.getClass();
  HashMap<S, Field> map;
  synchronized(getOpt_cache) {
    map = getOpt_cache.get(c);
    if (map == null)
      map = getOpt_makeCache(c);
  }
  ret map;
}