Check if date between date range that also handle null values Java

Question

My standard method for checking if a date is between two dates in Java looks like this:

public static boolean isWithinRange(Date date, Date startDate, Date endDate) {
    return !(date.before(startDate) || date.after(endDate));
}

I want to add support for null values on startDate or endDate (meaning user hasn't entered a date. If startDate is null I only want to check endDate and if endDate is null I only want to check startDate and if both null then it is true. My current solution looks like this:

public static boolean isWithinRange(Date date, Date startDate, Date endDate) {
    if (startDate == null && endDate == null) {
        return true;
    }

    if (!(startDate != null || !date.after(endDate))) {
        return true;
    }

    if (!(endDate != null || !date.before(startDate))) {
        return true;
    }

    return !(date.before(startDate) || date.after(endDate));
}

alternative more readable example:

public static boolean isWithinRange(Date date, Date startDate, Date endDate) {
    if (startDate == null && endDate == null) {
        return true;
    }

    if (startDate == null && date.before(endDate))) {
        return true;
    }

    if (endDate == null && date.after(startDate))) {
        return true;
    }

    return date.after(startDate) && date.before(endDate));
}

But it feels like really bad code. Is there any other way to deal with this?

Bullace

All the !'s are making it rather difficult for me to read. But you might consider whether this would be a better fit for codereview.stackexchange.com. – Helbonnas

It's to make it inclusive instead of strictly before and after. – Bullace

assylias’ answer is best, but the second version of your code is pretty reasonable. – Scilicet

Answer 1

How about:

return (startDate == null || !date.before(startDate))
    && (endDate == null || !date.after(endDate));

---

This uses the fact that these two statements are equivalent:

!(date.before(startDate) || date.after(endDate))
!date.before(startDate) && !date.after(endDate)

And the fact that || is a short-circuit, which prevents NullPointerExceptions.

Hamford

This is the cleanliest answer here. Might even use it myself since I have a similar case. – Merous

This seems to work. I added a null check for date too to avoid NPE. – Bullace

@Bullace I suspect a null date would be a bug so you could add Objects.requireNonNull(date); on the first line of your method. – Hamford

This will fail for null start & end dates and gives opposite results, – Josefajosefina

Answer 2

Java 8's enhances to the Comaparator interface provide a pretty elegant way of doing this:

private static final Comparator<Date> NULL_SAFE_BEFORE =
        Comparator.nullsFirst(Comparator.naturalOrder());

private static final Comparator<Date> NULL_SAFE_AFTER =
        Comparator.nullsLast(Comparator.naturalOrder());

public static boolean isWithinRange(Date date, Date startDate, Date endDate) {
    return NULL_SAFE_BEFORE.compare(startDate, date) < 0 &&
            NULL_SAFE_AFTER.compare(date, endDate) < 0;
}

Stairhead

Can you add some example code showing how to use this in the context of the Question? – Polak

@BasilBourque not sure what you mean - I did not change the signature of the isWithinRange method. Could you clarify what exactly you're asking? – Stairhead

Yes, I see that now. I misread you code, thinking you were quoting from the Comparator class rather than using it. – Polak

Answer 3

This should be equivalent:

public static boolean isWithinRange(Date date, Date startDate, Date endDate) {
    return !(startDate != null && date.before(startDate) || endDate != null && date.after(endDate));
}

Mellott