cyranoVR's Journal: Public Service Announcement

java.text.SimpleDateFormat and java.text.DecimalFormat are not thread-safe.

Thank you and Happy Holidays!

Really?

[ryanr]

I don't do Java at all.. but I'm a little surprised.

I don't track my own memory management, but I have to do my own concurrency access and thread management? Can you even do that well without being able to keep low-level records on which thread is modifying which memory?

Re:

[cyranoVR]

Yes, you do have to "track" your threads and think about concurrency in your code. However, this is not as bad as it sounds. Check out the following documentation:

java.lang.Thread [sun.com]

Also, Java 5 comes with a great concurrency library:
java.util.concurrent package description [sun.com]

How are you using them?

[FortKnox]

I just use their static methods "parse()" and "format()"....

Re:

[cyranoVR]

The defective code was written by one of my colleagues over two-years ago. I was tasked with resolving said defect.

Because our product is a highly-concurrent (hundreds of threads, thousands of transactions per second) messaging engine, I have learned to always think about threading anytime I'm writing a block of code that isn't strictly local scope.

Here's the code I had to fix (verbatim):

public class FormatUtils {

private static final dateFormat = new SimpleDateFormat("yyyyMMdd");