Re: [riena-dev] ListenerList vs ArrayList

[Alexander Ziegler <alexander.ziegler@xxxxxxxxxxxx>]

Hmm.. I don't see any use case.

Alexander


Am 27.08.08 09:31 schrieb "Stefan Liebig" unter
<Stefan.Liebig@xxxxxxxxxxxx>:

> Several points:
> - I think we are free to change (better extend) the behavior of our
> ListenerList to suit our needs
> - the original ListenerList already was policy driven, so why not widen
> the policy if we need it?
> - and again: what is the use case for adding a listener multiple times,
> and is this an indicator for some design flaw, unclear responsibilities,
> bla, bla, .. (don´t get me wrong, I am just asking)
> 
> Stefan
> 
> Christian Campo wrote:
>> I think we should agree on something (either duplicates or not). Now
>> you, Elias, removed the ListenerList to allow duplicates while
>> Thorsten just on monday replaced an ArrayList with the ListenerList.
>> 
>> There should be a unique policy throughout Riena. I am sure what the
>> policy is in Eclipse. I thought the ListenerList that we use is just
>> a copy of the class of Riena with an API that supports Generics. So
>> the "offiicial" class in Eclipse that should be used for Listeners
>> does not
>> allow duplicates (or better it ignores them).
>> 
>> If you ignore what could happen is that if you add the same listener
>> twice and then remove one, no listener is registered (since there is
>> no counter). So
>> can a programmer know that a listener he wants to register (this
>> particular instance) is already registered ? If he can, then he is
>> doing something wrong
>> registering it the second time. Its a little that we dont throw an
>> exception for duplicates then, but that is the way the Eclipse class
>> behaves.
>> 
>> IMHO I think since the ListenerList exists we should use it for each
>> and every case where a Listener is required. Since the original
>> implementation from
>> Eclipse ignores duplicates (and hence does not allow them), we could
>> think about throwing some kind of runtime exception and document that
>> duplicate
>> listeners are not allowed.
>> 
>> What do you guys think ?
>> 
>> christian
>> 
>> 
>> Am 27.08.2008 um 07:31 schrieb Stefan Liebig:
>> 
>>> We could also extend ListenerList to allow duplicates. There is
>>> already an enum Mode that could be
>>> extended for that.
>>> However, does it make sense for a listener to be notified multiple
>>> times for the same event?
>>> 
>>> Stefan
>>> 
>>> Volanakis, Elias wrote:
>>>> Just FYI, in the Tree/Table/List-Ridget I changed the container for the
>>>> double click listeners to ArrayList (recently changed to ListenerList).
>>>> The reason for using an ArrayList is that adding duplicate listeners is
>>>> explicitly permitted there.
>>>> 
>>>> This fixes the recent test failures in #testAddDoubleClickListener.
>>>> Feel free to discuss if you disagree. The alternative is to adjust the
>>>> tests / javadoc to disallow duplicate listeners.
>>>> 
>>>> Thanks,
>>>> Elias.
>>>> 
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>>> 
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