When is Singleton not a Singleton in Java?

Multiple singletons in two or more virtual machines

Multiple singletons simultaneously loaded by different class loaders

Singleton classes destroyed by garbage collection, then reloaded

Purposely reloaded singleton classes

Multiple instances resulting from incorrect synchronization

Multiple singletons arising when someone has subclassed your singleton

Copies of a singleton object that has undergone serialization and deserialization

Multiple singletons created by a factory specially asked to create multiple objects