private void release(){
  _pages.clear();
  _pages_rendered.clear();
  _error=null;
  _isWorking=false;
  file_name=null;
  file=null;
  if (_ringProgressDialog != null) {
    _ringProgressDialog.dismiss();
    _ringProgressDialog=null;
  }
}

private void release ( ) { _pages . clear ( ) ; _pages_rendered . clear ( ) ; _error = null ; _isWorking = false ; file_name = null ; file = null ; if ( _ringProgressDialog != null ) { _ringProgressDialog . dismiss ( ) ; _ringProgressDialog = null ; } }
release this class for future usage
