Grouse about Calendar, DateFormat, Date

[Nidhi Sar]

Does anyone else find Sun engineers' implementation of the dates classes as counter-intuitive as I do?
I just can't seem to remember anything because it runs so against what one would expect.

Some pet peeves:


1. When Calendar class and DateFormat class were meant to work in tandem, why doesn't the format() method of DateFormat take a Calendar instance as an argument? Why the need use a Date instance as a bridge?

2. Calendar class is full of umpteen utilities (methods & constants). So why not provide a simple method to find the difference between two Calendar dates? Why does every java programmer have to write his/her own utility of converting to milliseconds, finding the difference, dividing by 3600... and so on?

3. Why name the method of converting a Calendar date instance to a Date instance getTime()? Why not getDate()? [I can never ever remember it]. And oh, the getTime() method of Date it totally different, gives you back milliseconds, nothing to do with getTime() of Calendar.

I'm sure they have their own complicated reasons to do it this way, but I just can't figure out why.

[John de Michele]

1. When Calendar class and DateFormat class were meant to work in tandem, why doesn't the format() method of DateFormat take a Calendar instance as an argument? Why the need use a Date instance as a bridge?

That would be because DateFormat came out in JDK 1.0. Calendar didn't come out until JDK 1.1. Assuming that DateFormat and Calendar were meant to work together seems a bit presumptuous. Since Date has been around since JDK 1.0, it seems more likely that DateFormat was meant to work with Date.

John.

[Nidhi Sar]

John,

Thanks. That makes sense. But couldn't they just overload the format() method in new versions to include Calendar as an argument too, specially since it seems like they plan to deprecate the Date class as time goes by?

- Nidhi

[John de Michele]

Nidhi:

I suppose, but how hard is it to write this:

DateFormat dateFormat = new SimpleDateFormat();
Calendar calendar = new GregorianCalendar();
String date = dateFormat.format(calendar.getTime());

John.

[Nidhi Sar]

Not very! I'm just lazy

[John de Michele]

LOL . I seem to remember Larry Wall quoting laziness as a programming virtue.

John.

[Rob Spoor]

Nidhi, you should check out Joda time. I haven't used it myself yet, but a lot of people are recommending it over Java's own date/time system. I've even heard stories of Joda time being incorporated into the Java 7 core API.