The program uses double-checked locking to access a resource
					without the overhead of explicit synchronization, but the locking is
					insufficient.Double-checked locking refers to the situation where a programmer checks
						to see if a resource has been initialized, grabs a lock, checks again to see
						if the resource has been initialized, and then performs the initialization
						if it has not occurred yet. This should not be done, as is not guaranteed to
						work in all languages and on all architectures. In summary, other threads
						may not be operating inside the synchronous block and are not guaranteed to
						see the operations execute in the same order as they would appear inside the
						synchronous block.