I'm not completely up on generics.  I don't care for them all that much.
But from what I can see, you use extends to remove stuff from the
collection and super to add stuff to the collection.  extends creates a
child class, where super references the parent class.  it seems like a
hacky way to go about manipulating collections of generics, but the whole
generics systems feels like that to me.

On Sat, May 21, 2016 at 6:47 PM, trent shipley <trent.shipley@gmail.com>
wrote:

> "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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>>
>>
>>
>> --
>> James McPhee
>> jmcphe@gmail.com
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>
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-- 
James McPhee
jmcphe@gmail.com