Associate enum value to integer

Question

I have this enum:

public enum Digits {
    ZERO(0);

private final int number;

    private Digits(int number) {
        this.number = number;
    }

    public int getValue(){
        return number;
    }
}

And I would like to make setter in another class which can me offer following feature: - I will give it integer value (in this case, 0) and that setter will set enum ZERO to my local variable of type Digits Is that possible? Many thanks!

Possible duplicate of [Cast Int to enum in Java](http://stackoverflow.com/questions/5878952/cast-int-to-enum-in-java) — awesoon, Jan 19 '16 at 09:42
I don't understand your question. Can you clarify please what do you want to achieve? — Adam Arold, Jan 19 '16 at 09:42
One more duplicate candidate here: http://stackoverflow.com/questions/609860/convert-from-enum-ordinal-to-enum-type Please pay attention that using ordinal or numerical values of `enum` is potentially a bad idea. Why don't you use symbolic names? — nolexa, Jan 19 '16 at 09:49

Mena · Accepted Answer · 2016-01-19T09:44:55.863

It is possible, but not by invoking the enum's constructor, as it's available only within the enum itself.

What you can do is add a static method in your enum that retrieves the correct instance based on a given value, e.g. ZERO if the given value is 0.

Then you'd invoke that method in your other class when given the int argument.

Self contained example

public class Main {
    static enum Numbers {
        // various instances associated with integers or not
        ZERO(0),ONE(1),FORTY_TWO(42), DEFAULT;
        // int value
        private int value;
        // empty constructor for default value
        Numbers() {}
        // constructor with value
        Numbers(int value) {
            this.value = value;
        }
        // getter for value
        public int getValue() {
            return value;
        }
        // utility method to retrieve instance by int value
        public static Numbers forValue(int value) {
            // iterating values
            for (Numbers n: values()) {
                // matches argument
                if (n.getValue() == value) return n;
            }
            // no match, returning DEFAULT
            return DEFAULT;
        }
    }
    public static void main(String[] args) throws Exception {
        System.out.println(Numbers.forValue(42));
        System.out.println(Numbers.forValue(10));
    }
}

Output

FORTY_TWO
DEFAULT

Can you write it in Java? – user5507755 Jan 19 '16 at 09:43 — user5507755, Jan 19 '16 at 09:43

score 1 · Answer 2 · answered Jan 19 '16 at 09:43

1

You can do it like this:

private Digits digit;

public void setDigit(int number) {
    for (Digits value : Digits.values()) {
        if(value.getValue() == number) {
            digit = value;
        }
    }
}

answered Jan 19 '16 at 09:43

Mateusz Sroka

2,255
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19

score 1 · Answer 3 · answered Jan 19 '16 at 09:50

Here is the example how to achieve what you want

public enum Digit {

    ONE(1),
    TWO(2),
    THREE(3);

    private static final Map<Integer, Digit> mappingMap = new HashMap<Integer, Digit>();

    static {
        for (Digit m : Digit.values()) {
            mappingMap.put(m.getValue(), m);
        }
    }
    private final int digit;

    Digit(int aDigit) {
        digit = aDigit;
    }

    public int getValue() {
        return digit;
    }
    public static Digit getByDigit(int aDigit) {
        return mappingMap.get(aDigit);
    }
}

This approach has better performance than iterating over all constants for large enums.

Associate enum value to integer

3 Answers3