n be set on this object until this lock is released.<BR> 
Upgrading of the lock is not possible (thread holding a read lock can not upgrade it to exclusive lock).
This is done to prevent possible deadlocks caused by lock updates. 
But locks are reentrant - so thread can request the same lock many times (and correspondent number of unlocks is needed to release the lock).<BR> 
Locking the object doesn't prevent other threads from accessing the object - 
it only has influence on <code>sharedLock</code> and <co