"extends" used with a wildcard {"?"} such as SomeCollection<? extends T> makes sense to me.  After reading stackoverflow, I am only somewhat more enlightened on what SomeCollection<? super T> means, how it is used, and why one might want to use it.

Trent.

On Sat, May 21, 2016 at 6:18 PM James Mcphee <jmcphe@gmail.com> wrote:
Check the answer to this stackoverflow.  It says it better than I can.  http://stackoverflow.com/questions/3009745/what-does-the-question-mark-in-java-generics-type-parameter-mean

On Sat, May 21, 2016 at 1:08 PM, trent shipley <trent.shipley@gmail.com> wrote:

Can anyone tell me what the keyword "super" does in this parameter list for the constructor below? I can only find documentation for the more mundane use when a method references an ancestor.

public WeightedCollection(Comparator<? super E> comp)


package pcgen.base.util;

<</ deleted stuff>>

/**

* Constructs an empty WeightedCollection with the given Comparator used to

* establish equality and order in the WeightedCollection.

* @param comp

*            The Comparator this Set will use to determine equality and

*            order of the WeightedCollection

*/

public WeightedCollection(Comparator<? super E> comp)

{

     if (comp == null)

     {

          theData = new ListSet<WeightedItem<E>>();

     }

     else

     {

          theData = new TreeSet<WeightedItem<E>>(

                new WeightedItemComparator<E>(comp));

     }

} 



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