private void enableOperationButtons(){
  btnOr.setEnabled(true);
  btnAnd.setEnabled(true);
  btnRightParen.setEnabled(true);
}

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