Comments on: Java Date Validation is Annoying (Regexes too)

By: Matt Benson

Matt Benson — Mon, 18 Jun 2007 13:00:20 +0000

wrt your regexp example:

//given String input, String regex:

input.matches(regex) is a convenience method for:
Pattern.matches(regex, input)

which in turn is short for:
Pattern.compile(regex).matcher(input).matches()

If you’re looking for an occurrence as opposed to matching against the entire regex, use:
Pattern.compile(regex).matcher(input).find()

And of course there’s no reason not to cache the compiled Pattern in a real-world application.

By: P.Hill

P.Hill — Fri, 15 Jun 2007 23:28:47 +0000

Why does it work? 'cause SimpleDateFormat has the ability to deal with Medieval dates!
Thus you need to explicitly check for that.

GregorianCalendar cal = new GregorianCalendar();

try {
Date date = sdf.parse(str);
cal.setTime(date);
int year = cal.get(Calendar.YEAR);
if (year

By: jason

jason — Thu, 07 Jun 2007 19:44:02 +0000

Or you could just use SimpleDateFormat("MM-dd-yy") to parse for both 2 and 4 digit years.

Example. This will always work in the first block.

public static void main(String[] args) {

String dateIn = "01-01-3020";

SimpleDateFormat sdf1 = new SimpleDateFormat("MM-dd-yy");
SimpleDateFormat sdf2 = new SimpleDateFormat("MM-dd-yyyy");

Date myDate = null;

try {
myDate = sdf1.parse(dateIn);
System.out.println("ONE");
} catch (ParseException e) {
try {
myDate = sdf2.parse(dateIn);
System.out.println("TWO");
} catch (ParseException e1) {
System.out.println("Date Format Error");
}
}

System.out.println(myDate);
}