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From Daniel Shane <sha...@LEXUM.UMontreal.CA>
Subject Re: LowerCaseFilter, is there a reason why the class is final?
Date Fri, 11 Sep 2009 12:33:07 GMT
With the current API of TokenStream (incrementToken) I really do not see 
how I could do the following scenario with the Decorator Pattern :

I have a case where I would like to execute the LowerCaseFilter only if 
the token is of type "word". I do not want to execute the 
LowerCaseFilter if the token is of type "number" for example.

Unfortunately, I don't see how this is possible using the current API 
and the fact that the filters are final.

The only thing I can do is add a filter before the LowerCaseFilter that 
would pass all the non-word tokens to the next filter, but it seems 
really complicated for a case where a simple extend would do the job.

Or, if the API had two methods, one which increments the stream and 
another which process the current "token" or attributes then it would be 
possible to do what I have in mind using the Decorator Pattern.

Does anyone else see a way of doing this that is simple?

Daniel Shane

Uwe Schindler wrote:
> See https://issues.apache.org/jira/browse/LUCENE-1753
>
> In general, if you want to add functionality plug another filter into the
> chain. At least the implementations should be final (next/incrementToken).
>
> -----
> Uwe Schindler
> H.-H.-Meier-Allee 63, D-28213 Bremen
> http://www.thetaphi.de
> eMail: uwe@thetaphi.de
>
>
>   
>> -----Original Message-----
>> From: Daniel Shane [mailto:shaned@LEXUM.UMontreal.CA]
>> Sent: Thursday, September 10, 2009 4:06 PM
>> To: java-dev@lucene.apache.org
>> Subject: LowerCaseFilter, is there a reason why the class is final?
>>
>> Hi all,
>>
>> I was wondering why the LowerCaseFilter is declared final? In my code, I
>> would like to extend it but apparently its not possible. I'm just
>> wondering why extending this type of class is considered evil?
>>
>> Daniel Shane
>>
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>
>
>
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