null value for a date throwing a NullPointerException
if (aDate.after(cottageHospital.getLastWardChangeDate(thePatient)))
{
Ward newWard = (Ward) changeWardNewWardList.getSelectedValue();
changeWardArea.setText("Patient " + thePatient + " moved to " +
newWard + "ward.");
cottageHospital.changeWard(thePatient, newWard, aDate);
}
I have an if statement that is part of a larger method, the statement compares a date, aDate, with another date value. Problem is that the first time this method is used the date that aDate is trying to compare to is null, throwing a NullPointerExCeption.
What would be the best way to go about handling this exception?
您可以添加空检查：
theDate = cottageHospital.getLastWardChangeDate(thePatient);
if (theDate != null && aDate.after(theDate))
You should not handle the exception but make sure it does not appear at all -> make sure aDate never is null. If this is not possible, add a null check before the comparison.
Null check would look like this:
if (aDate != null && aDate.after(cottageHospital.getLastWardChangeDate(thePatient))) {
Ward newWard = (Ward) changeWardNewWardList.getSelectedValue();
changeWardArea.setText("Patient " + thePatient + " moved to " + newWard + "ward.");
cottageHospital.changeWard(thePatient, newWard, aDate);
}
Cleaner way would be to make sure aDate never is null though.
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