Cannot get date RegEx mm/dd/yyyy down in java

Question

My attempt is [0-1][0-9]\\/[0-3][0-9]\\/[1-2][0-9]{3} but 13+ is not a month and neither is 31+ a day. Any help would be appreciated

I wrote a [long answer](http://stackoverflow.com/a/22702401/2736496) about validating numeric ranges with regex. Not because it's a good idea, because it's not, rather because it's interesting from a learning regex point of view. — aliteralmind, Mar 28 '14 at 21:19

score 3 · Answer 1 · edited May 23 '17 at 12:20

3

Use a try/catch block where you extract the month and day, and then based on the parsed parameters, throw an illegalargument exception. Your situation definitely falls under the circumstances of when to throw such an exception as described here:

When should an IllegalArgumentException be thrown?

Thanks!

edited May 23 '17 at 12:20

Community

1
1

answered Mar 28 '14 at 00:32

user3470765

83
5

user2864740 · Answer 2 · 2014-03-28T01:00:33.910

Two steps, one less problem¹

Capture data which follows a specific format

The regular expression itself is then trivially (\d{2})/(\d{2})/(\d{4}) - the point is to check the format, not the validity, and capture the relevant data.

Validate the captured data

int year = Integer.parse(m.groups(3));
// ..
if (!validDate(year, month, day)) { .. }

Imagine how terrible it would be to try and also validate leap years with a regular expression alone; yet doing so with the above capture-validate is relatively trivial.

¹ This is a (Y) answer, because it assumes that actual code is also allowed. However, the "real life" correct solution (Z) would be to use existing date parsing support in Java or Joda Time, etc.

Cannot get date RegEx mm/dd/yyyy down in java

2 Answers2