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Re: string case clauses

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Peter Duniho wrote:
> Roedy Green wrote:
>> [...]
>> I understood the way string case labels worked posted earlier was to
>> use the hashCode as the switch variable, which would necessitate the
>> use of the inefficient lookupswitch plus a little kludge to deal with
>> hashCode collisions.
>>
>> In contrast a String case lookup done manually with HashMap does not
>> involve any binary search or linear scan.  It folds the hashCode to a
>> reasonable value and does a table lookup. [...]
> 
> I agree with Patricia's assessment.  There is no proof that the current 
> implementation of an integral switch would be less efficient than a full 
> hash table implementation, and in fact for relatively few values (as a 
> switch really ought to be), it's likely to be more efficient.  At the 
> very least, it's difficult to easily get a small hash table without also 
> having collisions.
> 
> I see no reason to be concerned whatsoever about the performance 
> implications of the choice of implementation for string case labels in 
> Java.  If and when you have a program where that turns out to be a 
> bottleneck, then of course you can look at alternatives.  I doubt you'll 
> run into that situation though.  And if you do, it's quite likely that 
> you should have been using a hash table structure for other reasons anyway.

These points or similar were made fairly early in this thread by a couple of people.

A 'switch' by any other name is still a 'goto'.

But at least it's forward only.

-- 
Lew

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string case clauses Roedy Green <see_website@mindprod.com.invalid> - 2011-09-11 09:35 -0700
  Re: string case clauses Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-09-11 12:00 -0500
    Re: string case clauses Roedy Green <see_website@mindprod.com.invalid> - 2011-09-11 15:33 -0700
      Re: string case clauses Arne Vajhøj <arne@vajhoej.dk> - 2011-09-11 21:56 -0400
        Re: string case clauses Lew <lewbloch@gmail.com> - 2011-09-11 20:54 -0700
          Re: string case clauses Arne Vajhøj <arne@vajhoej.dk> - 2011-09-12 18:58 -0400
      Re: string case clauses Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-09-11 20:05 -0700
        Re: string case clauses Roedy Green <see_website@mindprod.com.invalid> - 2011-09-14 12:13 -0700
          Re: string case clauses Patricia Shanahan <pats@acm.org> - 2011-09-14 12:36 -0700
          Re: string case clauses Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-09-14 18:01 -0700
            Re: string case clauses Lew <lewbloch@gmail.com> - 2011-09-14 20:05 -0700

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