In other words, the synchronization on these methods is used solely for its communication effects, not for mutual exclusion. While the cost of synchronizing on each iteration of the loop is small, there is a correct alternative that is less verbose and whose performance is likely to be better. The locking in the second version of StopThread can be omitted if stopRequested is declared volatile. While the volatile modifier performs no mutual exclusion, it guarantees that any thread that reads the field will see the most recently written value:
