[java-gnome-hackers] Singleton implementation in java (was Re: sourceview development branch)

[Vreixo F. <met...@ya...>]

Hi!

> > > The only thing that really caught my eye so far was
> > > LanguageManager.getDefault(); 
> 
> [...]
> 
> > Another option would be to turn LanguageManager into a real
> singleton [...]. The
> > LanguageManager would then be accessed like this:
> > LanguageManager.getInstance(); that does not remove the static
> method but would make it more explicit that you are using one. Maybe
> that would fit better?
> 
> Nah, not really.
> 

I also hate singleton pattern in the way it is teached (and commonly
used) in Java language. I'm now using an alternative that is much
better, imho: expose instance methods as static. I mean, if you have a
LanguageManager singleton, with a method getLanguage(), as in your
example instead of calling:

LanguageManager.getDefault().getLanguage("java")

you write:

LanguageManager.getLanguage("java")

Internally, LanguageManager keeps a reference of the single instance,
and delegates all methods in that instance. It could be something like
this:

public final class LanguageManager {

    // single instance
    private static final LanguageManager instance = new
LanguageManager();


    // private constructor
    private LanguageManager() {
    }

    // private instance methods
    private XXX getLanguage(String l) {
	....
    }

    // and public static methods...
    public static XXXX getLanguage(String l) {
	//... that delegate on the instance
	return instance.getLanguage(l)
    }

}


In my opinion this creates clear code, but I know everybody is using the
getInstance() traditional approach...

Cheers
Vreixo