Re: How to sort a Set?

From:

Lew <lew@lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 23 Jul 2008 10:27:13 -0700 (PDT)

Message-ID:

<8d0257f0-ab2c-41f1-aac7-61991214e1c3@e53g2000hsa.googlegroups.com>

On Jul 23, 1:05 pm, "Mike Schilling" <mscottschill...@hotmail.com>
wrote:

laredotornado wrote:

Hi,

I have a Set of Strings for which I'd like to sort, so that when I
iterate over the set, I'm doing so in sorted order.

Hashtable<String,Hashtable<String,String>> apps = getA=

pps();

java.util.Set<String> allowedApps = apps.keySet();
Iterator<String> i = allowedApps.iterator();

How can I sort the data? Thanks, - Dave

Youi could use a TreeMap instead of a Hashtable, and the iterator
would return the keys in sorted order automatically.

One should avoid Hashtable unless one, a) needs synchronization and,
b) needs all that extra non-Collections cruft.

The performance characteristics of TreeMap might be suboptimal. If
the need for sorted access is sufficiently rare, or the underlying Map
changes sufficiently infrequently, one could use idioms along the
lines of

  SortedMap <String, String> apps = new TreeMap <String, String>
( getApps() );

or

  Map <String, String> apps = getApps();
  SortedSet <Map.Entry <String, String>> sortedEntries =
    new TreeSet <Map.Entry <String, String>> ( apps.entrySet() );

or

  Map <String, String> apps = getApps();
  SortedSet <String> sortedKeys = new TreeSet <String>
( apps.keySet() );

--
Lew