Your logic makes sense to me ;-)
Stephen
----- Original Message -----
From: "Janek Bogucki" <[EMAIL PROTECTED]>
To: "Jakarta Commons Developers List" <[EMAIL PROTECTED]>
Sent: Sunday, September 07, 2003 2:35 AM
Subject: [collections] CollectionUtils.getCardinalityMap JavaDoc
> In CollectionUtils.getCardinalityMap the documentation notes the meaning
of an entry that maps to null but I don't see how any such entry can exist
in the returned map as all the keys in the map come from the collection
parameter and will map to >=1. Have I missed something?
>
> >From CollectionUtils v 1.36
>
> /**
> * Returns a [EMAIL PROTECTED] Map} mapping each unique element in
> * the given [EMAIL PROTECTED] Collection} to an [EMAIL PROTECTED] Integer}
> * representing the number of occurences of that element
> * in the [EMAIL PROTECTED] Collection}.
> * An entry that maps to <tt>null</tt> indicates that the
> * element does not appear in the given [EMAIL PROTECTED] Collection}.
> */
> public static Map getCardinalityMap(final Collection col) {
> HashMap count = new HashMap();
> Iterator it = col.iterator();
> while(it.hasNext()) {
> Object obj = it.next();
> Integer c = (Integer)(count.get(obj));
> if(null == c) {
> count.put(obj,new Integer(1));
> } else {
> count.put(obj,new Integer(c.intValue() + 1));
> }
> }
> return count;
> }
>
>
> -Janek
>
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