You can do this kind of thing using some methods in the random package in
[math]. See
http://jakarta.apache.org/commons/math/api/org/apache/commons/math/random/RandomData.html#nextSample(java.util.Collection,
int) for a way to sample from a collection. By using sample size = 1, you can
select a single random element.
You can iterate over a list in a random order by first generating a random
permutation using
http://jakarta.apache.org/commons/math/api/org/apache/commons/math/random/RandomData.html#nextPermutation(int,
int) and then using the resulting int[] array to select elements.
If random lists generated from collections are of interest, we could add a
method to do this directly. You can post any ideas on improving / extending
commons math here:
http://wiki.apache.org/jakarta-commons/MathWishList
Phil
-----Original Message-----
From: Stephen Colebourne [mailto:[EMAIL PROTECTED]
Sent: Thu 3/10/2005 4:54 PM
To: Jakarta Commons Developers List
Cc:
Subject: Re: [Collections] Random iterator?
We don't have such a method or iterator at present. I would like to keep
[collections] for deterministic not random effects if possible.
Stephen
----- Original Message -----
From: "Hernan Silberman" <[EMAIL PROTECTED]>
> In my unit and load tests, I often find myself retrieving a
collection of
> objects from a service, and selecting a random one from the
collection.
> Seems
> like a common use case (for testing anyhow) and I don't think there's
any
> support in java.util Collections for, say, fetching a random item out
of a
> Set.
> It's easy enough to code by hand, but I was wondering if it's already
done
> somewhere in commons-collections. A Random iterator would be really
cool.
>
> I suppose:
>
> List theList = new ArrayList( someCollection );
> Collections.shuffle( theList );
> Iterator theIt = theList.iterator();
>
> works fine too..
>
> thnx...
> hernan
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