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Re: A third easy performance optimisation needed

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On Thu, 13 Jul 2017 09:54:56 +0200, Cecil Westerhof wrote:

> I am going to give a presentation about how to easily improve the
> performance of your Java programs. Two subjects I already have are using
> final and being careful with autoboxing. I would like a third one.
> Anyone a good suggestion?

If you need both keyed random access and sequential access to a medium to 
large collection of objects, use a TreeMap rather than loading the data 
into flat structure (ArrayList) and sorting it because:

- a TreeMap efficiently inserts objects in key sequence

- walking a TreeMap is quite an efficient way of visiting objects 
  in key sequence

- keyed retrieval becomes progressively more efficient as the collection
  size grows. If the collection contains 2^n items, you only need n key
  comparisons to find a given key, so 4 comparisons if the tree holds 16
  items but only 23 comparisons if it holds 8 million items.
    
This is because TreeMap is implemented as a red-black binary tree. This 
is a self-balancing tree structure. See Sedgewick: "Algorithms" for a 
discussion of how it works.


-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 09:54 +0200
  Re:A third easy performance optimisation needed omegajunior <omegajunior@protonmail.com> - 2017-07-13 06:29 -0400
  Re: A third easy performance optimisation needed Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-13 11:27 +0000
  Re: A third easy performance optimisation needed Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-07-13 07:41 -0400
    Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 05:48 -0700
      Re: A third easy performance optimisation needed Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 19:39 -0400
    Re: A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 15:14 +0200
      Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 07:07 -0700
        Re: A third easy performance optimisation needed Robert Klemme <shortcutter@googlemail.com> - 2017-07-13 19:58 +0200
          Re: A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 20:02 +0200
  Re: A third easy performance optimisation needed Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 08:16 -0400
    Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 06:08 -0700
      Re: A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 15:41 +0200
        Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 07:09 -0700
          Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 08:07 -0700
          Re: A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 18:37 +0200
        Re: A third easy performance optimisation needed Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2017-07-13 13:19 -0500
          Re: A third easy performance optimisation needed Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 14:32 -0400
      Re: A third easy performance optimisation needed Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 13:52 -0400
        Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-14 07:52 -0700
  A third easy performance optimisation needed lewbloch@gmail.com - 2017-07-14 14:47 -0700

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