Concurrent JUnit testing

I have a large JUnit test suite, where I'd quite like to run all the tests concurrently for two reasons:

• Exploit multiple cores to run the whole test suite faster
• Hopefully detect some errors due to non-thread-safe global objects

I recognise that this will force me to refactor some code to make it thread-safe, but I consider that to be a good thing :-)

What's the best way to get JUnit to run all the tests concurrently?