groovy/groovy-core — pull request #60 by johnnywey (2012-08-07 18:44:08+00:00)
Title: Made JsonOutput thread safe by moving SimpleDateFormat to a ThreadLocal

This will safely allow the use of the SimpleDateFormat class in a multi-threaded environment. I would typically add a test for this, but duplicating a large amount of concurrent calls typically does not result in a great unit test.

I did, however, create a **very** crude failing script at https://gist.github.com/3279736 which does demonstrate the problem.

Thanks!