Getting a random element from an Enum

[Cate van Alphen]

Hi,

What I am trying to do is get a random element out of an enum, the array equivalent is:

int i = (int)(Math.random() * 10);
String s = array[i];    

I found enum has an ordinal() function that returns its position in its enum declaration, but I can't figure out how to get an object out using the position. The best I've come up with is this, given an enum called Season:

List< Season > seasonList = new ArrayList<Season>();

for ( Season s : EnumSet.allOf( Season.class )){
seasonList.add( s );

}

Season randomSeason = seasonList.get(i);    

which seems terribly clunky, I wondered if there was an easier way.

[James Sabre]

Given an enum say
enum X {a,b,c,d,e,f}
then

 
        Random random = new Random();
        for (int i = 0; i < 10; i++)
        {
            X randomX = X.values()[random.nextInt(X.values().length)];
            System.out.println(randomX);
        }

[Cate van Alphen]

Thanks. I'm a bit confused about where the .values() comes from. In the api I can find an abstract class Enum, but you declare an enum, is this different, and if so where do I find info about it? Is X.values() an array of the enum X?

[Jesper de Jong]

Every enum has an automatically generated values() method that returns all the enum values in an array. You won't find it in class Enum<E extends Enum<E>> - the compiler just automatically generates it. Note that the values() method of an enum type is static.

Is X.values() an array of the enum X?
Yes.

More info: Java 5.0 Language Features - Typesafe Enums

[Ilja Preuss]

Originally posted by Cate van Alphen:
I'm a bit confused about where the .values() comes from.

From the Java Language Specification...