Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!aioe.org!eternal-september.org!feeder.eternal-september.org!.POSTED!not-for-mail
From: markspace <-@.>
Newsgroups: comp.lang.java.help
Subject: Re: Dynamic enums
Date: Wed, 12 Oct 2011 07:46:49 -0700
Organization: A noiseless patient Spider
Lines: 44
Message-ID: <j7498t$pcn$1@dont-email.me>
References: <4e94eeb1$0$16274$9a566e8b@news.aliant.net> <j72sn7$cl$1@dont-email.me> <j72t18$1u6$1@dont-email.me> <4e952d5d$0$14660$9a566e8b@news.aliant.net> <j73vgl$n1o$1@dont-email.me>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Wed, 12 Oct 2011 14:46:53 +0000 (UTC)
Injection-Info: mx04.eternal-september.org; posting-host="XjIWM99mD7Ijfdu600oVPA"; logging-data="26007"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19ALjaryK7eLQQL4d4IMR5yuDxiHbYpIU8="
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1
In-Reply-To: <j73vgl$n1o$1@dont-email.me>
Cancel-Lock: sha1:3h22qeA1pVPGKTqstKCvggOMd/Y=
Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.help:1247

On 10/12/2011 4:58 AM, Eric Sosman wrote:

> Stepping back a bit, it's not clear to me why you need a separate
> data structure just to hold the keys. In your original post you wrote
> of pairings in "a table called foobar," matching A with 1, B with 2,
> and so forth. This sounds very much like a Map with entries {A,1},
> {B,2} and so on,


Because if the "enums" are dynamic, he needs someplace to store them. 
IF the database table lists enums as strings or ints, he needs a place 
to lookup up "A" or 1 and get the singleton class back that represents 
the enum.

Regular singleton:

class MyEnum {
   public static final MyEnum A = new MyEnum();
   public static final MyEnum B = new MyEnum();

   private MyEnum() {}
}

Dynamic:

class MyEnum {
   private MyEnum() {}

   private final HashMap enums = new HashMap();

   public void addEnum( String name ) {
     if( enums.get( name ) == null )
       enums.put( name, new MyEnum() );
   }

   public MyEnum getEnum( String name ) {
     return enums.get( name );
   }
}

Probably need some fields for getting the name of the enum or it's 
ordinal value, but that's how I see the out line of the dynamic part of 
the code.