Fool java into printing something it should not print

The goal of this series of puzzles (eg: http://wouter.coekaerts.be/2012/puzzle-clowns, http://wouter.coekaerts.be/2012/puzzle-dreams) is to trick java to return unexpected or explicitly forbidden results.

and..... I'm stuck. I think it has something to do with spawning new threads so that private fields can be forced into unexpected states, but I'm not sure how.