Re: Named fields in enum constant declarations

From:
rossum <rossum48@coldmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Wed, 15 Apr 2009 21:35:19 +0100
Message-ID:
<33hcu4pdi50n350cg15n1r4nnh0nvqpds8@4ax.com>
On Wed, 15 Apr 2009 10:56:37 -0700, Patricia Shanahan <pats@acm.org>
wrote:

In order to build a data visualization, I need to associate both an
arbitrary integer and a color with each of several conditions. Sounds
like a job for an enum. As currently written, I have unnamed Color
constructor calls as arguments in the enum constant declarations, e.g.

TRUE_POSITIVE(new Color(100, 255, 100))

I would prefer to replace that with something like:

TRUE_POSITIVE(LIGHT_GREEN)

but I don't know where to put the declaration:

private static final LIGHT_GREEN = new Color(100,255,100);

The enum syntax requires the enum constant declarations to be the first
thing in the body. They cannot forwards reference a field declaration.
The actual colors are naturally private to the enum - the rest of the
program just knows the fact that each enum constant has a method that
returns the associated color.

What am I missing? What is the right way to do this?

Patricia

How about:

    public enum MyColor {
        LIGHT_GREEN(100, 255, 100),
        BLACK(Color.BLACK);
                
        private final Color mHue;
        
        // Constructors
        MyColor(int r, int g, int b) {
            mHue = new Color(r, g, b);
        }
        
        MyColor(Color hue) {
            mHue = hue;
        }
        
        // Getter
        public Color getColor() {
            return mHue;
        }
    }

See Bloch, 2nd edition, Item 30.

rossum

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