Gets an item from the cache or creates it if not already existing. If
the item was found in the cache, its access time is updated, otherwise
its create time is set.
Note that the create time is set only if an item is created, not if it
already existed and you change the value referenced by the returned
reference.
a reference to the value of the obtained or created item. If an item
was created, the returned reference may refer to the value of a
previously removed element.
Gets an item from the cache or creates it if not already existing. If the item was found in the cache, its access time is updated, otherwise its create time is set.
Note that the create time is set only if an item is created, not if it already existed and you change the value referenced by the returned reference.