So you mean to say that a single copy of instance will be shared between all the instantiating class objects. Right? I think you may be getting confused about what a Singleton is and how it works.
When some code asks for a n instance of a Singleton it does not actually "instantiate" it. It just asks for one, usually by calling a static method somewhere. If an instance has already been created, that's the one it gets. Client code should never call "new" on a Singleton class, that's one of the key things which make it a Singleton.
Depending how the Singleton class is coded, the instance may be created when the Singleton's class is loaded into the JVM, or the instance may be created as a side effect the first time some client code asks for an instance. In practice, that doesn't really matter.
As a side note, please be aware that the Singleton design
pattern is hugely over-used, and (in my opinion, and that of many people here) is almost never a good idea. Can you tell us any more about what you might be thinking of using a Singleton for?