Re: Initializing a Map in an Interface?

From:
Kevin McMurtrie <mcmurtrie@pixelmemory.us>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 16 Mar 2010 08:58:34 -0700
Message-ID:
<4b9faaaa$0$22121$742ec2ed@news.sonic.net>
In article <lZKdnVdCN8aZ3QLWnZ2dnUVZ8vVi4p2d@eclipse.net.uk>,
 Ian Smith <ian.smith@gossinteractive.com> wrote:

Isn't this sort of thing that Enums and EnumMaps are meant for? Just
asking . . .

Ian.


Consider a situation where the design starts out using Enum but later
needs to load definitions from a configuration file. That can't be done
with Enum, EnumMap, or code that works with them. The original poster
mentioned having large sets of definitions of Colors so I think a design
using Enum would run into future problems.

If Enums were to be used for declaration of data that may later become
dynamic, I'd transfer them to a Map that had keys and values that aren't
Enums. Unfortunately the code isn't so clean now. Two classes must be
defined and they're both public.

import java.awt.Color;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

public interface FooColor
{
  enum NamedColorSet
  {
    Black (new Color(0, 0, 0)),
    Obscure_Gray (new Color(51, 51, 51)),
    Dark_Gray (new Color(102, 102, 102)),
    Light_Gray (new Color(153, 153, 153)),
    Pale_Gray (new Color(204, 204, 204)),
    White (new Color(255, 255, 255));
    
    public final Color color;
    NamedColorSet (Color c)
    {
      color= c;
    }
  }
  
  public static final Map<String, Color> EIGHT_BIT_COLORS =
    Collections.unmodifiableMap(new HashMap<String, Color>()
  {
    {
      for (NamedColorSet n : NamedColorSet.values())
        put (n.name(), n.color);
    }
  });
}
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