simple solution to Java Date/Calendar problems

[Bob Suruncle]

I know Java programmers are known for struggling with dates. Setting your personal life aside ;-) .....here's a simple solution to dealing with Calendar objects and parts thereof.

It's not uncommon for an HTML UI/presentation layer for example, to have a ONE based selection list for month and pass that to the underlying code.

At this point I think we should think in Java, as it's now in the Java realm and keep it ZERO based, but opinions vary.
Here's a simple solution, that I used when several developers had worked on the same project. It's not rocket science, it's semantics!... and meant I could peacefully co-exist with other work that had been done on the project.

Simply ensure that a variable or method has a J to indicate that it's a value that's in the Java realm, e.g.

int jMonth

So, May would be jMonth=4 or month=5. Then you quickly know if you need to do a +/-1 when using the variable.

or

String jMonthLabel(int jMonth){
where this code return Jan, Feb etc for a given Integer, expecting it to be passed as zero based.
}

As I said it's not rocket science, but it's saved me a lot of tracing back through code to find out what mood the developer was in that day! I can't change the world, but I can make it easier to live in. I'm sure others have already said this or are doing this, but posting it makes it easier to find on Google!

[Rob Spoor]

Or you simply use the Calendar constants like Calendar.JANUARY, Calendar.FEBRUARY etc.

As for converting those constant values into Strings, that's where DateFormatSymbols comes in:

String getMonthLabel(int month)
{ 
    DateFormatSymbols dfs = DateFormatSymbols.getInstance();
    String[] months = dfs.getShortMonths();
    String month = months[month];
    return month;
}

DateFormatSymbols has been designed to use the Calendar constants as array indexes. That's why, for instance, getWeekDays() returns a String[] where the first element is an empty String - because weekdays are 1-based.

For instance:

String monthLabel = getMonthLabel(Calendar.JANUARY); // "Jan"

And to top it off - it's locale specific if possible as well!

And please read your private messages.

[James Dixon]

Personally I've always found Joda Time to be a great tool to use when it comes to messing around with dates.
It always seemed to be a bit more intuative than the Java API's offering