Given the numeric value of a particular enum type, how can I retrieve the name?

Question

I'm trying to set up my enum so that it has a list of names and retrieve a particular name given that value.

Example: enum {Vanilla, Chocolate, Strawberry};

Given 0, return Vanilla. Given 1, return Chocolate. Given 2, return Strawberry.

I haven't been able to find any methods that come with the Java Enum class to do this out of the box. I'm thinking of writing my own that dumps the values into an array and then use binary search to return them, given a particular number.

Is there something built in however that would be better?

Thanks!

Konstantin Yovkov · Answer 1 · 2013-05-23T21:04:08.303

3

You have to implement it in the Enum. Like this:

public enum MyEnum {
  VANILLA(0), CHOCOLATE(1), STRAWBERRY(2);

  private int i;

  private MyEnum(int i) {
     this.i = i;
  }

  public static MyEnum getFoodById(int id) trhows IllegalArgumentException {
     MyEnum result = null;
     switch (id):
       case 0: {
         result = MyEnum.VANILLA;
         break;
       }
       case 1: {
         result = MyEnum.CHOCOLATE;
         break;
       }
       case 2: {
         result = MyEnum.STRAWBERRY;
         break;
       }
       default : { 
          throw new IllegalArgumentException("Invalid id ...");
       }
   }
   return result;
}

edited May 23 '13 at 21:04

answered May 23 '13 at 20:22

Konstantin Yovkov

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This is right because is not a good idea to use the "internal index" of the enum than can change if you refactor the code (reordening the list). In this way you are sure of what number is assigned to every object. – ERNESTO ARROYO RON May 23 '13 at 20:32
Of course. Vote up :) – Konstantin Yovkov May 23 '13 at 20:33
1

+1 for the correct approach. – Ravi K Thapliyal May 23 '13 at 20:40
That won't work... actually even compile for that matters. `i` in the switch should be `id`. – Jonathan Drapeau May 23 '13 at 21:03
Can you tell me what the pro's/ cons are over this approach over a for loop(as in my answer below)? Having to add a case every time we add an enum seems like an unnecessary overhead. It also has the potential to create bugs in your code? – Michael W May 24 '13 at 13:22
I agree. Just wrote it like that for the specific case. :) – Konstantin Yovkov May 24 '13 at 13:28

score 3 · Answer 2 · answered May 23 '13 at 20:29

3

If your id corresponds to the enum item's position, you can use the built-in values() and ordinal()-Methods.

// to enum
int intValue = 0;
CustomEnum item = CustomEnum.values()[intValue];

// to int
CustomEnum item = CustomEnum.SOME_ITEM;
int intValue = item.ordinal();

answered May 23 '13 at 20:29

Sean Patrick Floyd

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It is not a good practice to use the internal values of the enum, can change if you reorder the list in the source code. – ERNESTO ARROYO RON May 23 '13 at 20:33
That's why I wrote "If your id corresponds to the enum item's position" – Sean Patrick Floyd May 23 '13 at 20:39

score 2 · Answer 3 · answered May 23 '13 at 20:28

2

You can use EnumMap. You can look at here for solution and example.

answered May 23 '13 at 20:28

Sukumar

21
1

Michael W · Answer 4 · 2013-05-24T13:13:03.873

1

You can also do it this way:

public enum IntEnum {

Vanilla(0), Chocolate(1), Strawberry(2);

private int value;

IntEnum(int value) {
    this.value = value;
}

public int getValue() {
    return value;
}

public static IntEnum getEnum(int intValue) {
    Integer value = intValue;

    if (value == null)
        throw new IllegalArgumentException();
    for (IntEnum v : values())
        if (value.equals(v.getValue()))
            return v;
    throw new IllegalArgumentException();
}



public static void main(String[] args) {

    System.out.println(IntEnum.getEnum(1));         
}

}

edited May 24 '13 at 13:13

answered May 23 '13 at 20:33

Michael W

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1

Should use `int` directly instead of `Integer`, avoid the possibility of the `null` value passed to your method. – Jonathan Drapeau May 23 '13 at 21:07

score 0 · Answer 5 · answered May 23 '13 at 20:22

0

Enums do allow for built in functions.

public enum Flavor
{
    VANILLA("Vanilla"),
    CHOCOLATE("Chocolate"),
    STRAWBERRY("Strawberry");

    private final String desc;

    Flavor(String desc)
    {
        this.desc = desc;
    }

    public String getDesc()
    {
        return desc;
    }
}

answered May 23 '13 at 20:22

Bill Clar

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9

How's this related to the question? – Luiggi Mendoza May 23 '13 at 20:33

score 0 · Answer 6 · answered May 23 '13 at 20:25

0

public enum Flavor {
    Vanilla, Chocolate, Strawberry
}

Flavor v = Flavor.values()[0];

String name = v.name(); // "Vanilla"

http://docs.oracle.com/javase/6/docs/api/java/lang/Enum.html#name()

answered May 23 '13 at 20:25

Tom Fobear

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This is not how enums work in java. – FDinoff May 23 '13 at 20:27
@FDinoff what do you mean by that? – Sean Patrick Floyd May 23 '13 at 20:29

score 0 · Answer 7 · answered May 23 '13 at 20:27

0

Use the values() result:

enum Flavours {Vanilla, Chocolate, Strawberry}

assertTrue(Flavours.Vanilla == Flavours.values()[0]);

answered May 23 '13 at 20:27

rolfl

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Given the numeric value of a particular enum type, how can I retrieve the name?

7 Answers7