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Re: Design Patterns

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On 05/02/13 05:03, Peter Duniho wrote:
> On 5 Feb 2013 04:10:11 GMT, Stefan Ram wrote:
>
>> Arne Vajhøj<arne@vajhoej.dk>  writes:
>>>> Pattern or anti-pattern, I never encountered a situation where I felt a
>>>> need for »singletons«.
>>> Other have.
>>
>>    Maybe someone can come up with an SCSE where a singleton is needed.
>
> _Needed_ is situation-specific, but examples generally will include
> situations where multiple callers require access to some shared resource
> abstracted by the singleton class. In some cases, a static class suffices.
> But in other cases it's either useful or required to have a singleton (e.g.
> because you need the singleton to implement an interface, something static
> classes in Java can't do).

OK, I know I'm probably still being ignored because I've upset some 
people but can someone please explain to me exactly what a 'static 
class' is (WRT Java of course)

This is illegal

public static class Foo{...

a class with all static methods certainly can implement an interface

This compiles

public class Foo implements Serializable{
    public static void Bar(){
    }
}

So what makes a class 'static enough' so that it can't implement an 
interface ? (for example)

As for a Singleton

Well some years ago I went for an interview
The interviewer showed me the following line of code(or something like it)

private final Integer var = 10;

He asked me what I thought of it.

I said it was a flag to future maintainers that this value was important 
and should not be changed without fully understanding the implications.

I got the job (after lots more questions of course)

And this is one reason I think I might use a singleton

In a system with potentially many statics a Singleton (hopefully) stands 
out. It makes explicit the intentions of the developer.
People who understand design patterns will understand what a Singleton 
is, if you like it's a form of documentation.

As for an example (I think this has been mentioned before).
I seem to remember back in the day writing a database connection pool 
manager as a Singleton. Why ? well it probably seemed like a good idea 
at the time :-)

just my 2 euros worth

lipska

-- 
Lipska the Kat©: Troll hunter, sandbox destroyer
and farscape dreamer of Aeryn Sun

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Design Patterns dougmmika@gmail.com - 2013-02-02 16:17 -0800
  Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-02 19:39 -0500
    Re: Design Patterns Marcel Müller <news.5.maazl@spamgourmet.org> - 2013-02-03 18:52 +0100
      Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-03 14:23 -0800
      Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:57 -0500
        Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-09 11:10 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-09 19:36 -0500
            Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-09 23:44 -0800
              Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-09 23:47 -0800
                Re: Design Patterns "John B. Matthews" <nospam@nospam.invalid> - 2013-02-10 12:28 -0500
              Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-10 13:35 -0500
              Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-10 13:36 -0500
                Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-10 23:12 -0800
          Re: Design Patterns "John B. Matthews" <nospam@nospam.invalid> - 2013-02-09 19:45 -0500
  Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-02 20:17 -0500
  Re: Design Patterns Doug Mika <dougmmika@gmail.com> - 2013-02-02 19:43 -0800
    Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-02 20:54 -0800
      Re: Design Patterns Doug Mika <dougmmika@gmail.com> - 2013-02-02 21:11 -0800
        Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-03 08:24 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:41 -0500
    Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-02 21:57 -0800
  Re: Design Patterns Roedy Green <see_website@mindprod.com.invalid> - 2013-02-03 06:38 -0800
  Re: Design Patterns Joerg Meier <joergmmeier@arcor.de> - 2013-02-04 17:06 +0100
    Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-04 12:38 -0800
    Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-04 21:31 -0500
      Re: Design Patterns Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-02-04 21:03 -0800
        Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-04 21:25 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 19:54 -0500
            Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-05 17:51 -0800
              Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:54 -0500
        Re: Design Patterns lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-05 09:43 +0000
          Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-05 13:03 -0800
            Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:09 -0500
          Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-05 13:56 -0800
            Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-05 14:30 -0800
            Re: Design Patterns Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-02-05 14:33 -0800
            Re: Design Patterns lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-06 09:03 +0000
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:07 -0500
      Re: Design Patterns Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-02-05 09:10 -0500
        Re: Design Patterns Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-02-05 13:20 -0500
          Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-05 13:10 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:11 -0500
      Re: Design Patterns Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-02-05 09:53 -0800
        Re: Design Patterns Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-02-05 20:17 -0400
        Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 19:50 -0500
      Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:34 -0500
        Re: Design Patterns Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-02-06 08:40 -0800
          Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:38 -0500
    Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-04 21:41 -0500

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