static Map<Class, Field[]> getDeclaredFields_cache = newDangerousWeakHashMap();

static Field[] getDeclaredFields_cached(Class c) {
  Field[] fields;
  synchronized(getDeclaredFields_cache) {
    fields = getDeclaredFields_cache.get(c);
    if (fields == null) {
      getDeclaredFields_cache.put(c, fields = c.getDeclaredFields());
      for (Field f : fields)
        makeAccessible(f);
    }
  }
  ret fields;
}