throws Throwable
  public boolean usort(Env env,                       ArrayValue array,                       Callback func,                       @Optional long sortFlag)    throws Throwable  {    if (array == null)      return false;    if (!func.isValid()) {      env.warning(L.l("Invalid comparison function"));      return false;    }    CompareCallBack cmp;    cmp = new CompareCallBack(ArrayValue.GET_VALUE, SORT_NORMAL, func, env);    array.sort(cmp, KEY_RESET, STRICT);    return true;  }