[collections] Sort map by value

[Willie Vu <ct...@ust.hk>]

I've a map where the key is to lookup an item and the value is a title for
display.  The titles are not unique.  I want to sort the map by the titles.
SortedMap only sorts by key.  DoubleOrderedMap forces values to be unique.
Neither satisfies my requirement.  Does anyone know a map implementation
that does what I want?

--
Willie Vu
 

RE: [collections] Sort map by value

[Thomas Muller <tt...@online.no>]

Seems like the association between item and title is so strong that the
title should be an inherent part, but anyway...

I don't know of any map implementations that facilitates sorting by values,
but you can always sort it on demand:

private static Comparator ENTRY_VALUE_COMPARATOR = new Comparator() {

        public int compare( Object o1, Object o2 ) {
            return ( ( Comparable ) ( ( Map.Entry )
o1 ).getValue() ).compareTo( ( ( Map.Entry ) o1 ).getValue() );
        }

   }

Map.Entry[] entries = ( Map.Entry[] ) map.entrySet().toArray( new
Map.Entry[ 0 ] );

Arrays.sort( entries, ENTRY_VALUE_COMPARATOR );

If you want to keep the entries in a sorted structure, you need to maintain
a sorted list / queue parallell to the map. I've attached a couple of
homegrown classes: SortedList and SimpleSortedList you can play with if you
want to.

Hope this helps,

--

Thomas



| -----Original Message-----
| From: Willie Vu [mailto:ctwillie@ust.hk]
| Sent: 06 February 2003 07:28
| To: commons-user@jakarta.apache.org
| Subject: [collections] Sort map by value
|
|
| I've a map where the key is to lookup an item and the value is a title for
| display.  The titles are not unique.  I want to sort the map by
| the titles.
| SortedMap only sorts by key.  DoubleOrderedMap forces values to be unique.
| Neither satisfies my requirement.  Does anyone know a map implementation
| that does what I want?
|
| --
| Willie Vu
|
|
|
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| To unsubscribe, e-mail: commons-user-unsubscribe@jakarta.apache.org
| For additional commands, e-mail: commons-user-help@jakarta.apache.org
|
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