Is there a way to add methods to GregorianCalendar in Java?

Question

I'd like to make a method called "isBetween" returning a boolean, seeing if a GregorianCalendar date falls between two others. Alternatively, I'd like to just define operators of < and > for the class. I'm pretty new to Java, so I'm not sure....can I even do either of those? If so, how?

Answer 1

Java does not support monkeypatching or operator overloading, but feel free to subclass GregorianCalendar and add whatever methods you need.

But then, do you really need a new method to do cal.after(startCal) && cal.before(endCal) ?

Answer 2

No, you can't add method to pre-existing classes and you can't do operator overloading either in Java.

As an alternative, you could provide a static utility method in your own class for example.

Answer 3

I would advise against extending the class - you're not adding any behaviour which is specific to instances of a particular class, you're expressing logic which is applicable for any GregorianCalendar (or possibly any calendar at all).

As Joachim says, a static method in a utility class is the way to go - and if Java ever gains extension methods as per C# (I know they were suggested for Java 7, but I think they're out at the moment) you can modify them at that point.

Oh, and use Joda Time anyway :)

Answer 4

You should try to extend it:

class MyGregorianCalendar extends GregorianCalendar