Re: Sorting TimeZone

From:
Lew <noone@lewscanon.com>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 02 Nov 2009 20:17:27 -0500
Message-ID:
<hco0b8$4vk$1@news.albasani.net>
Wojtek wrote:

How would you sort timezones?


Do you mean 'java.util.TimeZone'?

I am trying to sort them according to their offset from UTC. I cannot
use a TreeMap because there are many timezones with the same offset,
which of course over-writes the previously put timezone.


There's no "of course" about that if you are using your "preferred sort".

Why would you use any kind of 'Map' rather than a 'Collection'?

The preferred sort would be offset, then display name.


'TimeZone' can easily be a map key, yes, even for a 'TreeMap'. I fail to see
the problem. You simply compare based on your "preferred sort".

I'd be more concerned about relocation of a key when the offset changes for
DST. But perhaps you're only building this structure for a given moment in
time and that isn't a concern for you.

Regardless, here's uncompiled, off-the-cuff code, using a 'Set' instead of a
'Map':

  public class SortedZone
  {
    private long ref = System.currentTimeMillis();

    private final TreeSet <TimeZone> zones =
     new TreeSet <TimeZone>
     ( new Comparator <TimeZone> ()
       {
         @Override public int compare( TimeZone t0, TimeZone t1 )
         {
           return
           (t0 == null? (t1 == null? 0: -1)
           : t1 == null? 1
           : t0.getOffset( ref ) > t1.getOffset( ref )? 1
           : t0.getOffset( ref ) < t1.getOffset( ref )? -1
           : t0.getDisplayName().compareTo( t1.getDisplayName() )
           );
         }
       }
     );

    // cover methods for the Set ...
  }

--
Lew

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