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From: Martin Gregorie <martin@address-in-sig.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: Inserting In a List
Date: Wed, 3 Apr 2013 22:43:51 +0000 (UTC)
Organization: UK Free Software Network
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On Wed, 03 Apr 2013 02:04:19 +0200, Joerg Meier wrote:

> On Tue, 2 Apr 2013 22:52:20 +0000 (UTC), Martin Gregorie wrote:
> 
>> On Tue, 02 Apr 2013 18:22:55 -0400, Eric Sosman wrote:
>>> On 4/2/2013 5:06 PM, Martin Gregorie wrote:
>>>>[...]
>>>> Its also not clear to me whether the OP is expecting some form of
>>>> sorted list of filenames. If he is expecting that, it would be best
>>>> to use a TreeMap<String> rather than an ArrayList<String> to store
>>>> the filenames.
>>>      Is there a reason to prefer TreeMap (or other SortedMap) over
>>> accumulate-disordered-and-sort-afterward?
>> I think so, yes, because none of File's list() and listFiles() methods
>> guarantee the order of the returned files. By using TreeMap or
>> equivalent the OP gets the sort for free, should it be required.
> 
> For free ?
>
I meant in terms of coding effort.

> The cost is just distributed amongst the insert calls, and is
> likely considerably higher than with an unsorted list that has a single
> sort call once it is filled.
>
Not necessarily so (see above) and that's why I specified a TreeMap 
rather than any other type of ordered map because of the relative drop in 
access costs as the collection size increases.

> SortedMaps are for things that need sorting
> accessible before all elements are inserted
>
And isn't the case with the TreeMap either - red-black binary trees have 
rather nice characteristics there.

> Java doesn't have ArrayMaps.
>
Yeah, I meant ArrayList and should have been obvious from the context 
provided by the OP.


-- 
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gregorie. | Essex, UK
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