please include function getOpt_cached.

// Some people use this.
static Field setOpt_findField(Class c, S field) {
  HashMap<S, Field> map;
  synchronized(getOpt_cache) {
    map = getOpt_cache.get(c);
    if (map == null)
      map = getOpt_makeCache(c);
  }
  ret map.get(field);
}

static void setOpt(Object o, String field, Object value) ctex {
  if (o == null) ret;
  
  ifclass _SetField
    if (o instanceof _SetField) ret with o/_SetField._setField(field, value);
  endif
  
  Class c = o.getClass();
  HashMap<S, Field> map;
  
  if (getOpt_cache == null)
    map = getOpt_makeCache(c); // in class init
  else synchronized(getOpt_cache) {
    map = getOpt_cache.get(c);
    if (map == null)
      map = getOpt_makeCache(c);
  }
  
  if (map == getOpt_special) {
    if (o instanceof Class) {
      setOpt((Class) o, field, value);
      ret;
    }
    
    // It's probably a subclass of Map. Use raw method. TODO: huh?
    setOpt_raw(o, field, value);
    ret;
  }
  
  Field f = map.get(field);
  ifdef setOpt_debug
  printVars_str(+c, +field, +f);
  endifdef
  if (f != null)
    ret with smartSet(f, o, value); // possible improvement: skip setAccessible
  ifclass DynamicObject
    if (o cast DynamicObject)
      ret with setDyn(o, field, value);
  endif
  if (o cast IMeta)
    setDyn(o, field, value);
}

static void setOpt(Class c, String field, Object value) {
  if (c == null) ret;
  try {
    Field f = setOpt_findStaticField(c, field); // TODO: optimize
    if (f != null)
      smartSet(f, null, value);
  } catch (Exception e) {
    throw new RuntimeException(e);
  }
}
  
static Field setOpt_findStaticField(Class<?> c, String field) {
  Class _c = c;
  do {
    for (Field f : _c.getDeclaredFields())
      if (f.getName().equals(field) && (f.getModifiers() & java.lang.reflect.Modifier.STATIC) != 0) {
        makeAccessible(f);
        return f;
      }
    _c = _c.getSuperclass();
  } while (_c != null);
  ret null;
}

Began life as a copy of #1000891