No monitor for immutable class instances?

[Steven Schveighoffer]

On Mon, 11 Mar 2013 21:54:46 -0400, bearophile <bearophileHUGS at lycos.com>  
wrote:

> Maybe a stupid question: an immutable class instance can't change, so is  
> it possible and is it a good idea to remove (to not add) the monitor  
> pointer field from immutable class instances, saving memory and allowing  
> them to store one more word in the same amount of memory?

Both immutable and mutable cast to const.  A const function may be  
accessing mutable data in a read-only fashion, but it still may need to  
lock the monitor.  Therefore, you must still be able to lock an immutable  
object.

-Steve