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I am receiving return value in the form of long or int from Native code in Android, which I want to convert or match with enum, for processing purpose. Is it possible ? How?

Jim G.
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Sachchidanand
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2 Answers2

65

If you have full control of values and enums, and they're sequential, you can use the enum ordinal value:

enum Heyo
{
  FirstVal, SecondVal
}

...later

int systemVal = [whatever];
Heyo enumVal = Heyo.values()[systemVal];

int againSystemVal = enumVal.ordinal();
Kevin Galligan
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    Use of the ordinal to get a "value" for an enum is not recommended. Instead, use an instance field instead. See Item 31 in the 2nd edition of Josh Bloch's Effective Java. – Vito Andolini Nov 04 '16 at 20:24
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    Why is not recommended? – Robin Davies Jun 02 '18 at 15:05
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    @RobinDavies If someone (ie. from your team) will add value in the middle or beginning it will mess up whole code using .ordinal() – callmebob Nov 06 '18 at 16:22
  • Instead of saying not recommended, let's just note that the values will change if the enum is modified. Changing the order of the enums, adding new ones or removing existing ones has the potential to change the values of the entire sequence. If you program your logic around these values, then changing them might break your code. If that's ok with you then have fun. – Raslanove Mar 22 '23 at 13:50
63

You can set up your enum so it has the long or int built into it.

e.g: Create this file ePasswordType.java

public enum ePasswordType {

    TEXT(0),
    NUMBER(1);

    private int _value;

    ePasswordType(int Value) {
        this._value = Value;
    }

    public int getValue() {
            return _value;
    }

    public static ePasswordType fromInt(int i) {
        for (ePasswordType b : ePasswordType .values()) {
            if (b.getValue() == i) { return b; }
        }
        return null;
    }
}

You can then access the assigned values like this:

ePasswordType var = ePasswordType.NUMBER;

int ValueOfEnum = var.getValue();

To get the enum when you only know the int, use this:

ePasswordType t = ePasswordType.fromInt(0);

Enums in java are very powerful as each value can be its own class.

Kuffs
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    This is a much better approach than using ordinal(). To learn why, read Effective Java – David Snabel-Caunt Nov 07 '11 at 12:36
  • @Kuffs: Is there also a proper way to **set** the enum by using the integer value? – Levite Dec 15 '14 at 14:42
  • @Levit The value is set at design time not run time. If you mean retrieve the enum value when you only know the int, see my edited answer. – Kuffs Dec 16 '14 at 08:48
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    @DavidSnabel-Caunt Could I impose on you to save me the cost and trouble of acquiring Effective Java for the sole purpose of finding out why ordinal() is bad, and provide an explanation. – Robin Davies Jun 02 '18 at 15:08
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    @robin-davies check out this question. https://stackoverflow.com/questions/44654291/is-it-good-practice-to-use-ordinal-of-enum – Kuffs Jun 03 '18 at 15:58