question: public void notifyThreadFree ( final Thread thread ) { if ( thread == null ) { return ; } synchronized ( activationLock ) { synchronized ( mainLock ) { busyThreadSet . remove ( thread ) ; if ( isReadyToShutdown ( ) ) { mainLock . notifyAll ( ) ; timeoutPassed = false ; } } } }
target:  Remove a specified thread from the set of busy event dispatch threads. If this set doesn't contain the specified thread or the thread is null, the call leaves this set unchanged and returns silently.