RE: [Rails-devel] Stock market revisited

[Stewart T. <wsr...@ho...>]

Erik,

>2. StockMarket is a singleton and should IMO be constructed as such.
>This means: private constructors, access only via a static get()
>method that returns the one instance (which is created the first time,
>or from a static init block).
>In addition to safety, this removes the need to pass around object
>variables,
>as each class needing access to the stockmarket object can get it
>immediately by calling StockMarket.get().

Please think very carefully that you understand the implications of making 
the constructor "private" in Java when creating a singleton class. A class 
with a private constructor is implicitly final and cannot be extended with a 
subclass. As long as you want to prohibit subclasses of your singleton, then 
this is fine. However, if there is a possibility that it might be useful at 
some point for someone to create a subclass, then it is better to make the 
constructor "protected".

Please note, I'm not suggeesting that StockMarket should not be a singleton, 
I'm simply making an observation about Java style and behaviour.

You're going to be busy this weekend... have fun... I'm off skiing, so I'll 
b ehaving fun too!

cheers

Stewart