private void disableOperationButtons(){
  btnOr.setEnabled(false);
  btnAnd.setEnabled(false);
  btnRightParen.setEnabled(false);
}

private void disableOperationButtons ( ) { btnOr . setEnabled ( false ) ; btnAnd . setEnabled ( false ) ; btnRightParen . setEnabled ( false ) ; }
convenience method for disabling the buttons related to filter operations for filtering ( btnand , btnor , etc )
