Initializing Java enum properties with a function?

Question

I have an enum in Java 8 with Lombok's @Getter and @AllArgsConstructor for using additional properties for the enum value:

@Getter
@AllArgsConstructor
public enum MyEnum {
    RED(1),
    GREEN(2),
    BLUE(3),
    PURPLE(4);
    
    private final int ordinal;
    
    public String getDisplayName() {
        switch (ordinal) {
            case 1:
                return "1st color";
            case 2:
                return "2nd color";
            case 3:
                return "3rd color";
            default:
                return "another color";
        }
    }
}

What I don't like about this solution: getDisplayName() is called quite often, thus every call runs the switch-case statement.

Is it possible to add another property like displayName which values are set by a function analogous to getDisplayName()?

Something like this (pseudo-code):

@Getter
@AllArgsConstructor
public enum MyEnum {
    RED(1, setDisplayName()),
    GREEN(2, setDisplayName()),
    BLUE(3, setDisplayName()),
    PURPLE(4, setDisplayName());
    
    private final int ordinal;
    private String displayName;
    
    private void setDisplayName() {
        switch (ordinal) {
            case 1:
                displayName = "1st color";
            case 2:
                displayName = "2nd color";
            case 3:
                displayName = "3rd color";
            default:
                displayName = "another color";
        }
    }
}

"which values are set by a function analogous to getDisplayName()" why not just have a second instance variable called displayName and add that string to the constructor? So that you can do something like public enum MyEnum { RED(1, "1st color"), GREEN(2, "2nd Color").... — Federico klez Culloca
– Federico klez Culloca, Commented Mar 17, 2021 at 21:02
@FedericoklezCulloca Yes, that would be a way I could go for a relatively small amount of enum values. If the enum grows in size, I'd like to avoid this. — Robert Strauch
– Robert Strauch, Commented Mar 17, 2021 at 21:05
Ah, now I think I see the problem. You're worried about the values you don't have in the switch statements and how they would go to default? — Federico klez Culloca
– Federico klez Culloca, Commented Mar 17, 2021 at 21:08
In that case I would go with a constant for the default values. I mean, if your alternative was to add a call to a method for each of the enum values I don't see much difference :) either that or you could remove @AllArgsConstructor and provide your own one-argument constructor that does the switch part and assigns the correct value to displayName — Federico klez Culloca
– Federico klez Culloca, Commented Mar 17, 2021 at 21:12
@RobertStrauch, not to be picky, but ordinal is a terrible choice for that constant field. It leads to confusion because Enums have already a field name ordinal. — hfontanez
– hfontanez, Commented Mar 17, 2021 at 21:19

Federico klez Culloca · Accepted Answer · 2021-03-17 21:29:34Z

2

If you're not married to lombok I would just provide my own constructor and let it do the heavy lifting

@Getter
public enum MyEnum {
    RED(1),
    GREEN(2),
    BLUE(3),
    PURPLE(4);
    
    private final int o;
    private final String display;
    
    private MyEnum (int o) {
        this.o = o;
        switch (o) {
            case 1:
                display = "1st color";
                break;
            case 2:
                display = "2nd color";
                break;
            case 3:
                display = "3rd color";
                break;
            default:
                display = "another color";
        }
    }
}

Also changed ordinal to o as per @hfontanez suggestion.

edited Mar 17, 2021 at 21:29

answered Mar 17, 2021 at 21:21

Federico klez Culloca

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Comments

Edgar Domingues · Accepted Answer · 2021-03-17 21:14:48Z

1

You could do something like this:

@Getter
@AllArgsConstructor
public enum MyEnum {
    RED(1, setDisplayName(1)),
    GREEN(2, setDisplayName(2)),
    BLUE(3, setDisplayName(3)),
    PURPLE(4, setDisplayName(4));

    private final int ordinal;
    private String displayName;

    private static String setDisplayName(int ordinal) {
        switch (ordinal) {
            case 1:
                return "1st color";
            case 2:
                return "2nd color";
            case 3:
                return "3rd color";
            default:
                return "another color";
        }
    }
}

The setDisplayName method may even be in another class.

answered Mar 17, 2021 at 21:14

Edgar Domingues

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Comments

olz · Accepted Answer · 2021-03-17 22:23:18Z

1

you can just call the method in the constructor

@Getter
public enum MyEnum {
    RED(1),
    GREEN(2),
    BLUE(3),
    PURPLE(4);
    
    private final int ordinal;
    private final int displayName;

    MyEnum(int ordinal) {
      this.ordinal = ordinal;
      this.displayName = getDisplayName(ordinal);
    }

    
    public static String getDisplayName(int ordinal) {
        switch (ordinal) {
            case 1:
                return "1st color";
            case 2:
                return "2nd color";
            case 3:
                return "3rd color";
            default:
                return "another color";
        }
    }
}

answered Mar 17, 2021 at 22:23

olz

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