/**
* A helper function that obtains the total number of hours for the selected period.
*
* @return Total number of hours.
* @throws InsufficientDataException Thrown if the total is zero.
*/
private double checkTotal() throws InsufficientDataException {
double total = Double.parseDouble(totalLabel.getText());
if (total == 0) throw new InsufficientDataException("Cannot submit data with no logged hours.");
return total;
}
