Groups > comp.lang.java.programmer > #2601

Re: Enums: Properties vs. Methods

From	Robert Klemme <shortcutter@googlemail.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: Enums: Properties vs. Methods
Date	2011-03-30 20:00 +0200
Message-ID	<8vh9efFg01U1@mid.individual.net> (permalink)
References	<2f38bb8e-9a8d-4464-ad3d-b9ce0b557219@e21g2000yqe.googlegroups.com> <imsutq$115$1@news.albasani.net>

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On 29.03.2011 17:47, Lew wrote:
> On 03/29/2011 11:18 AM, Robert Klemme wrote:
>> All,
>>
>> I am just musing about the pros and cons of using boolean properties
>> in enum classes vs. custom methods. So far I found
>>
>> pro Properties:
>> - less classes
>
> How is that a pro?

The reasoning was that then less space in Perm is needed.

>> - when adding enum values to an enum you cannot forget to define
>> properties
>
>> pro Methods:
>> - smaller memory footprint per instance
>
> You actually don't know what the footprint will be once Hotspot takes
> over. With your "toy" example, those booleans might all optimize away
> and both cases take the same memory at runtime.

Just so I understand it properly: are you saying that with hotspot the 
compiler might remove members of the instances?  I am not sure how that 
would work since then hotspot would need to create several different 
versions of the property getter methods (one per instance).  I believe 
this is not what hotspot can do.

>> Considering that there are always only so many instances it seems the
>> properties approach wins. It seems, custom methods in enum instances
>> are most useful if enums do actually do something. Then different
>> enums can have differing implementations of the method and we have an
>> instance of Strategy / State pattern.
>>
>> Do you have more items for the lists? Did I overlook something?
>
> Your example didn't make a good case for why you'd want do do such a thing.

Right.

> Your "methods" example is confusing and the purpose behind the logic
> deeply obscured by the idioms. That alone is enough to kill it. Your
> "properties" example was clear and concise and easy to follow.
>
> No-brainer.

Well, roughly speaking the idea was this:
https://gist.github.com/892503#file_valve.java

Here there are boolean properties which derive from the enum, i.e. 
whether there is traffic allowed or not and whether the traffic can flow 
unlimited.

Now code which uses this enum need not create switches based on concrete 
enum instances but can use boolean properties in control flow (e.g. 
print a warning if no traffic at all is allowed).  One might later want 
to add another enum value BROKEN(false, false) which is used to describe 
the state of a broken medium.  If this is done the code that uses those 
properties to make decisions does not need to be extended.

Cheers

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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Enums: Properties vs. Methods Robert Klemme <shortcutter@googlemail.com> - 2011-03-29 08:18 -0700
  Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-03-29 11:47 -0400
    Re: Enums: Properties vs. Methods Robert Klemme <shortcutter@googlemail.com> - 2011-03-30 20:00 +0200
      Re: Enums: Properties vs. Methods Lew <lew@lewscanon.com> - 2011-03-30 13:17 -0700
        Re: Enums: Properties vs. Methods Robert Klemme <shortcutter@googlemail.com> - 2011-03-31 00:48 -0700
          Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-03-31 08:41 -0400
            Re: Enums: Properties vs. Methods Robert Klemme <shortcutter@googlemail.com> - 2011-03-31 08:26 -0700
              Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-03-31 22:16 -0400
                Re: Enums: Properties vs. Methods Robert Klemme <shortcutter@googlemail.com> - 2011-04-02 11:56 +0200
                Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-04-02 10:29 -0400
                Re: Enums: Properties vs. Methods Robert Klemme <shortcutter@googlemail.com> - 2011-04-03 13:14 +0200
  Re: Enums: Properties vs. Methods markspace <-@.> - 2011-03-29 09:26 -0700
    Re: Enums: Properties vs. Methods Robert Klemme <shortcutter@googlemail.com> - 2011-03-30 20:06 +0200
      Re: Enums: Properties vs. Methods markspace <-@.> - 2011-03-30 12:40 -0700
        Re: Enums: Properties vs. Methods Robert Klemme <shortcutter@googlemail.com> - 2011-03-31 00:38 -0700
  Re: Enums: Properties vs. Methods Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-03-29 19:03 +0200
    Re: Enums: Properties vs. Methods Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-03-29 19:04 +0200
  Re: Enums: Properties vs. Methods Roedy Green <see_website@mindprod.com.invalid> - 2011-03-29 12:49 -0700
  Re: Enums: Properties vs. Methods Roedy Green <see_website@mindprod.com.invalid> - 2011-03-29 12:52 -0700
    Re: Enums: Properties vs. Methods Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-03-29 22:45 +0200
      Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-03-29 17:08 -0400
        Re: Enums: Properties vs. Methods Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-03-29 23:25 +0200
          Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-03-29 19:05 -0400
            Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-03-29 19:40 -0400
              Re: Enums: Properties vs. Methods Robert Klemme <shortcutter@googlemail.com> - 2011-03-31 02:57 -0700
                Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-03-31 08:52 -0400
                Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-03-31 08:54 -0400
            Re: Enums: Properties vs. Methods Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-03-30 18:40 +0200
              Re: Enums: Properties vs. Methods Lew <lew@lewscanon.com> - 2011-03-30 10:33 -0700
                Re: Enums: Properties vs. Methods Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-03-30 20:43 +0200
                Re: Enums: Properties vs. Methods Lew <lew@lewscanon.com> - 2011-03-30 13:20 -0700
                Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-03-31 08:55 -0400
  Re: Enums: Properties vs. Methods Wanja Gayk <brixomatic@yahoo.com> - 2011-04-02 11:23 +0200
    Re: Enums: Properties vs. Methods Lew <noone@lewscanon.com> - 2011-04-02 10:36 -0400
      Re: Enums: Properties vs. Methods Wanja Gayk <brixomatic@yahoo.com> - 2011-04-02 21:20 +0200

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