Re: Dynamic enums

From:
markspace <-@.>
Newsgroups:
comp.lang.java.help
Date:
Wed, 12 Oct 2011 07:46:49 -0700
Message-ID:
<j7498t$pcn$1@dont-email.me>
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.

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