Re: Random Enum

From:

Lew <lew@lewscanon.com>

Newsgroups:

comp.lang.java.help

Date:

Mon, 24 Aug 2009 15:05:02 -0700 (PDT)

Message-ID:

<20e4adfe-0c28-43c4-a8d2-29a8aea2087c@g6g2000vbr.googlegroups.com>

Daniel Berger wrote:

To get a Random enum you need something along those lines.

<code>
public Days randomDay() {
Days[] days = Days.values();

return days[(int) (Math.random() * days.length)];}

</code>

Or,

public class RandomDayer
{
  private static final Random rand = new Random();

  public static Days randomDay()
  {
    return Days.values() [rand.nextInt( Days.values().length )];
  }
}

But what if I want to generalize this code.
Is it possible that my method accepts just any enum, gets it's [sic]
.values, gets one Random value from it and returns it?

If you can pass a Class instance to the method, as Eric Sosman
suggested.

public class RandomEnum // untested, not even compiled yet
{
  private static final Random rand = new Random();

  public static <E extends Enum<E>> E random( Class <E> clazz )
  {
    E [] values = clazz.getEnumConstants();
    return values [rand.nextInt( values.length )];
  }
}

As to Eric's fear that this is "unpleasantly intricate", we just have
to get over it.

In use it's very simple. Given an enum 'Foo':

  Foo value = RandomEnum.random( Foo.class );

--
Lew