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Date: Fri, 12 May 2006 11:16:55 +0100
From: George Harley <george.c.harley@googlemail.com>
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To: harmony-dev@incubator.apache.org
Subject: Re: [classlib] Exception throwing compatibility
References: <002001c67586$d70c68e0$6501a8c0@OFFICEDESKTOP>
 <4464575A.5090606@googlemail.com> <200605121205.14702.chris.gray@kiffer.be>
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Chris Gray wrote:
> On Friday 12 May 2006 11:37, George Harley wrote:
>   
>> Nathan Beyer wrote:
>>     
>>> Note, the RI is NOT throwing ArrayIndexOutOfBoundsExceptions, it is just
>>> letting them happen via invalid array look ups, but in these cases, the
>>> specification is marked with an IndexOutOfBoundsException.
>>>       
>> Hi Nathan,
>>
>> If we consider the RI as a "black box" whose internals should be
>> completely hidden from us - a starting point that I think is important
>> to all participants of this project (and their legal representatives) -
>> then it does not matter *why* the RI is throwing the AIOOBE. It just does.
>>     
>
> Right, and in general we cannot know exactly which exception type the RI will 
> throw in any specific case - we have to start from the assumption that it 
> follows the spec, and take note of any deviations or more specific behaviour 
> that turns up. It's not possible to exhaustively test every exception case.
>   

Hi Chris,

Absolutely agree with you that we should not be looking to exhaustively 
test every exception case. We have to work in a mode where we respond to 
each deviation as we become aware of them.


>   
>> What will matter more to potential Harmony adopters ? Adherence to the
>> spec or ease of transition of their apps from the RI to Harmony ? In
>> this case we can satisfy the spec and enable runtime compatibility by
>> throwing the identical concrete exception type.
>>     
>
> If the app is written to the spec there's no problem. But in real life it can 
> happen that the developer doesn't look at the spec - during testing her code 
> throws an AIOOBE, so she adds an exception handler for that case. In this 
> case we make this (incorrect) app run by copying RI's behaviour (insofar as 
> we can determine what this is). But if RI throws 
> sun.util.FunnyIndexOutOfBoundsException and the programmer codes to this, 
> we're hosed - the app has to fixed.
>
> Chris
>   

Indeed. We can only throw something with the same 
public/non-implementation-specific supertype and hope for the best.

Best regards,
George


>
>   


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