Date parsing error

[Jason Purcell]

Hi there...

I am getting intermittent exceptions when parsing dates.

My formatter is declared as follows:

   SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
   dateFormat.setLenient(false);

These are some of the exceptions that have been thrown:

   java.text.ParseException: Unparseable date: "02/04/1980"
   java.text.ParseException: Unparseable date: "20/06/1985"
   java.text.ParseException: Unparseable date: "05/03/1990"
   java.text.ParseException: Unparseable date: "14/09/1973"
   java.text.ParseException: Unparseable date: "25/01/2011"
   java.text.ParseException: Unparseable date: "25/01/2011"
   java.text.ParseException: Unparseable date: "09/07/1965"
   java.text.ParseException: Unparseable date: "07/10/1974"
   java.text.ParseException: Unparseable date: "27/08/1966"

My unit tests pass when using the "unparseable" dates above, and in production dates parse correctly basically 99.999% of the time in the relevant piece of code.

As an example, the following dates parse correctly:

07/06/1978
14/06/1981
04/01/1988
03/10/1965
12/09/1977
30/01/1985

Has anyone come across this before?

Is there a problem with using SimpleDateFormat.setLenient() perhaps?

Regards,
Jason.

[Michael Wiles]

are you sharing the instance of SimpleDateFormat? It is in fact not thread safe - this might be causing your issue.

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[Bruce Stewart]

Hi Jason, the SimpleDateFormat class is not thread safe. If you were not aware of this you may have multiple threads accessing the the dateFormat instance, and this is exactly the sort of error that can occur.

[Jason Purcell]

I just read the same thing somewhere else now.

Always thought it was a good idea to re-use it, but I guess it's not.

Thanks for the info!!

I will implement the changes and see how things go.

[Dr Heinz M. Kabutz]

You could stick the instance in a ThreadLocal, that allows you to reuse it without worrying about concurrency.

Or you could use the Apache date parser.

Regards

Heinz
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Dr Heinz M. Kabutz (PhD CompSci)
Author of "The Java(tm) Specialists' Newsletter"
Sun Java Champion
IEEE Certified Software Development Professional
http://www.javaspecialists.eu
Tel: +30 69 72 850 460
Skype: kabutz 

[Jason Purcell]

Thanks.

I just made it non-static as a quick-fix.

[Dr Heinz M. Kabutz]

It's not static that's the problem, but multi-threaded access.  If your object is still being shared by multiple threads, you still have the bug in your code.

Regards

Heinz
-- 
Dr Heinz M. Kabutz (PhD CompSci)
Author of "The Java(tm) Specialists' Newsletter"
Sun Java Champion
IEEE Certified Software Development Professional
http://www.javaspecialists.eu
Tel: +30 69 72 850 460
Skype: kabutz 

[Gary Jacobson]

The simplest fix is to keep the SimpleDateFormat static, but instead of calling dateFormat.parse() directly, make a static synchronized parseDate() method to call it.

[Jason Purcell]

What I basically did was to make it an instance variable, and then have a static synchronized method that does the parsing.

I haven't been spending too thought on the problem, as it happens very rarely, and is not due to high load, but rather due to the client-side not handling double-clicks correctly.

But I will spend some time later today to fix it properly so that I will handle it correctly in the future.

Thanks for the help.