Re: Reverse sorting an array

Date	2011-09-30 16:58 -0700
From	Patricia Shanahan <pats@acm.org>
Newsgroups	comp.lang.java.help
Subject	Re: Reverse sorting an array
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On 9/30/2011 4:27 PM, Fred wrote:
> But I must be missing something obvious here - why does this print
> zeroes?
...
> 	printArray(positives, positivesIndex);
> 	Arrays.sort(positives);
> 	printArray(positives, positivesIndex);
...

Arrays.sort without a specified fromIndex and toIndex sorts the entire
array. I would expect to see (positives.length - positivesIndex) zero
elements before the first positive element in the sorted array.

Given the facts that you are reading a variable number of elements and
you need to do reverse sorting, are you *sure* you should be working
with int rather than Integer? If you used Integer, you could build up a
List exactly the right length, avoiding any extra zero elements. You
could use Collections.sort with the Collections.reverseOrder()
comparator to directly sort them in descending order. The whole thing
would be simpler.

At least so far, you are not doing any arithmetic that would need int,
and you don't have anywhere near enough elements for there to be a
significant performance difference.

Patricia

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Thread

Reverse sorting an array Fred <albert.xtheunknown0@gmail.com> - 2011-09-30 04:03 -0700
  Re: Reverse sorting an array Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-30 07:50 -0400
    Re: Reverse sorting an array Fred <albert.xtheunknown0@gmail.com> - 2011-09-30 15:24 -0700
      Re: Reverse sorting an array Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-30 20:50 -0400
        Re: Reverse sorting an array Roedy Green <see_website@mindprod.com.invalid> - 2011-10-01 19:38 -0700
          Re: Reverse sorting an array Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-01 22:58 -0400
            Re: Reverse sorting an array Lew <lewbloch@gmail.com> - 2011-10-01 20:21 -0700
    Re: Reverse sorting an array Fred <albert.xtheunknown0@gmail.com> - 2011-09-30 15:31 -0700
      Re: Reverse sorting an array Roedy Green <see_website@mindprod.com.invalid> - 2011-09-30 15:45 -0700
        Re: Reverse sorting an array Fred <albert.xtheunknown0@gmail.com> - 2011-09-30 16:27 -0700
          Re: Reverse sorting an array Patricia Shanahan <pats@acm.org> - 2011-09-30 16:58 -0700
    Re: Reverse sorting an array Roedy Green <see_website@mindprod.com.invalid> - 2011-09-30 15:43 -0700
      Re: Reverse sorting an array Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-30 20:57 -0400
  Re: Reverse sorting an array Roedy Green <see_website@mindprod.com.invalid> - 2011-09-30 04:58 -0700
    What qualifies as a constant ? (Was: Reverse sorting an array) Mayeul <mayeul.marguet@free.fr> - 2011-09-30 14:45 +0200
      Re: What qualifies as a constant ? (Was: Reverse sorting an array) Lew <lewbloch@gmail.com> - 2011-09-30 07:39 -0700
        Re: What qualifies as a constant ? (Was: Reverse sorting an array) Mayeul <mayeul.marguet@free.fr> - 2011-09-30 17:15 +0200
          Re: What qualifies as a constant ? (Was: Reverse sorting an array) Lew <lewbloch@gmail.com> - 2011-09-30 08:42 -0700

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