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Re: Question about HashMap and Map.Entry ...

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On 30.08.2012 23:55, Andreas Leitgeb wrote:
> Daniel Pitts <newsgroup.nospam@virtualinfinity.net> wrote:
>> On 8/30/12 12:32 PM, Andreas Leitgeb wrote:
>>> Damn, on re-read, I notice, that my own implementation of
>>> Map.Entry could just hold a ref to the map and implement
>>> setValue() to write the value back into the Map...
>> Or, if you know all the keys before hand, you can use instead Map<Long,
>> MyLongWrapper> map.
>
> I know all the relevant keys before hand. I currently do
> an initial map.put(k,0L) for each relevant "k".
>
>> MyLongWrapper would have .set() and .get(), or even .actUpon()
>> depending on the semantics you need.
>
> Indeed, that is a more elegant approach, than mine.
> Although it won't save me the extra containsKey(), as I'll
> be also having "k"s that aren't in the map,

containsKey() is unnecessary work.  Just get(), and if it's null create 
a new MyLongWrapper.  Btw, if you use long as member instead of Long 
then you do not even necessarily have more objects.

containsKey() is only ever useful if you have null values in a Map or 
are just interested in the fact whether a key is present or not.  Other 
than that just get() is more efficient even though effects might be 
negligible.

Cheers

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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Question about HashMap and Map.Entry ... Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-30 17:39 +0000
  Re: Question about HashMap and Map.Entry ... markspace <-@.> - 2012-08-30 10:46 -0700
    Re: Question about HashMap and Map.Entry ... Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-30 11:15 -0700
      Re: Question about HashMap and Map.Entry ... Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-30 19:24 +0000
        Re: Question about HashMap and Map.Entry ... Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-30 19:32 +0000
          Re: Question about HashMap and Map.Entry ... Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-30 13:08 -0700
            Re: Question about HashMap and Map.Entry ... Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-30 21:55 +0000
              Re: Question about HashMap and Map.Entry ... Robert Klemme <shortcutter@googlemail.com> - 2012-08-31 07:27 +0200
                Re: Question about HashMap and Map.Entry ... Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-31 10:26 +0000
                Re: Question about HashMap and Map.Entry ... Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-31 11:22 -0700
                Re: Question about HashMap and Map.Entry ... Robert Klemme <shortcutter@googlemail.com> - 2012-09-01 11:06 +0200
        Re: Question about HashMap and Map.Entry ... markspace <-@.> - 2012-08-30 14:30 -0700
          Re: Question about HashMap and Map.Entry ... Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-30 22:42 +0000
        Re: Question about HashMap and Map.Entry ... markspace <-@.> - 2012-08-30 14:34 -0700
  Re: Question about HashMap and Map.Entry ... Lew <lewbloch@gmail.com> - 2012-08-30 13:42 -0700
    Re: Question about HashMap and Map.Entry ... Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-30 22:34 +0000

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