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marcolopes
marcolopes

Reputation: 9287

Java: Getting an array of ENUM elements

Is there a better way of creating arrays from elements of an enum:

    public static enum LOGICAL {
        AND ("&", "AND"),
        OR ("||", "OR");

        public final String symbol;
        public final String label;

        LOGICAL(String symbol, String label) {
            this.symbol=symbol;
            this.label=label;
        }
    }

    public static final String[] LOGICAL_NAMES = new String[LOGICAL.values().length];
    static{
        for(int i=0; i<LOGICAL.values().length; i++)
            LOGICAL_NAMES[i]=LOGICAL.values()[i].symbol;
    }

    public static final String[] LOGICAL_LABELS = new String[LOGICAL.values().length];
    static{
        for(int i=0; i<LOGICAL.values().length; i++)
            LOGICAL_LABELS[i]=LOGICAL.values()[i].label;
    }

Upvotes: 6

Views: 11601

Answers (3)

ahmet alp balkan
ahmet alp balkan

Reputation: 45206

If you use your values very frequently and your enumeration gets bigger use Maps. Declare the following in your class.

private static EnumMap<LOGICAL,String> symbols = new EnumMap<LOGICAL, String>(LOGICAL.class);

and then just below it:

static{
    for(LOGICAL i : LOGICAL.values().)
        symbols.put(i, i.symbol);
}

then you can use symbols.values() or symbols.get(LOGICAL.AND) etc.

Upvotes: 2

Jon Skeet
Jon Skeet

Reputation: 1499900

Personally I wouldn't expose them as an array, whose contents can be changed by anyone. I'd probably use an unmodifiable list instead - and probably expose that via a property rather than as a field. The initialization would be something like this:

private static final List<String> labels;
private static final List<String> values;

static
{
    List<String> mutableLabels = new ArrayList<String>();
    List<String> mutableValues = new ArrayList<String>();
    for (LOGICAL x : LOGICAL.values())
    {
         mutableLabels.add(x.label);
         mutableValues.add(x.value);
    }
    labels = Collections.unmodifiableList(mutableLabels);
    values = Collections.unmodifiableList(mutableValues);
}

(If you're already using Guava you might even want to use ImmutableList instead, and expose the collections that way to make it clear that they are immutable.)

Upvotes: 3

Bozho
Bozho

Reputation: 597036

No. That seems the proper way. Even if there was some utility, it would rely on reflection

If you are using it often cache it in the enum

Upvotes: 2

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