Be careful about TreeMap though. If you have equivalency in the comparator it will remove one of the objects...
Read the javadocs carefully. sandeep --- Kris Schneider <[EMAIL PROTECTED]> wrote: > TreeMap: > Red-Black tree based implementation of the SortedMap > interface. This class > guarantees that the map will be in ascending key > order, sorted according to the > natural order for the key's class (see Comparable), > or by the comparator > provided at creation time, depending on which > constructor is used. > > SequencedHashMap: > A map of objects whose mapping entries are sequenced > based on the order in which > they were added. > > TreeMap implements SortedMap, SequencedHashMap does > not. You may also be > interested in looking at LinkedHashMap which was > added to Java in 1.4. > > Quoting Andrew Hill > <[EMAIL PROTECTED]>: > > > Didnt think to use a TreeMap - good idea! > > > > When accessed via the Map interface the difference > you perceive is one of > > implementation efficiency - the SequencedHashMap > uses a HashMap internally > > - > > and it entries also have references that will > preserve the list order, > > while > > a TreeMap uses a tree internally which of course > can be traversed in order. > > > > According to the docs, the HashMap will give you a > "fast O(1) search time" > > for lookups while the TreeMap has "guaranteed > log(n) time" - so I guess for > > a huge collection the HashMap would be faster. > That said I doubt your > > requirements approach anything like the size > needed for a noticable > > difference in lookup time, and HashMaps are noted > to be quite heavy when it > > comes to memory use so Id say the TreeMap is a > better choice. :-) > > > > -----Original Message----- > > From: O_Parthasarathy Kesavaraj > [mailto:[EMAIL PROTECTED] > > Sent: Tuesday, 8 July 2003 13:48 > > To: 'Struts Users Mailing List' > > Subject: RE: Urgent!!!Sorting Problem while > loading from HashMap > > > > > > Thanks Navjot and Andrew.. > > Meanwhile i tried to convert it to TreeMap.It is > working fine..But Andrew.. > > what is the difference between TreeMap and > SequencedHashMap b'coz TreeMap > > itself is giving me the list in order of how i > have stored > > Regds > > Partha > > > > > ---------- > > > From: Andrew > Hill[SMTP:[EMAIL PROTECTED] > > > Reply To: Struts Users Mailing List > > > Sent: Tuesday, July 08, 2003 10:45 AM > > > To: Struts Users Mailing List > > > Subject: RE: Urgent!!!Sorting Problem while > loading from HashMap > > > > > > HashMaps will rearrange stuff internally and > will NOT preserve the > > > original > > > order (see the j2se javadocs for details). > > > > > > There is a class in commons-collections (which > should already be on your > > > classpath as struts (1.1 anyway) uses this > library) called > > > SequencedHashMap - try using this instead as it > preserves the order in > > > which > > > stuff was added to the hashmap and uses this > order in its iterator. > > > > > > (This was introduced in commons-collections 2.0 > so if your using an older > > > version you may need to upgrade the jar with the > latest. > > > > > > Heres the javadoc for it: > > > > > > http://jakarta.apache.org/commons/collections/api/org/apache/commons/colle > > > ctions/SequencedHashMap.html > > > > > > -----Original Message----- > > > From: O_Parthasarathy Kesavaraj > [mailto:[EMAIL PROTECTED] > > > Sent: Tuesday, 8 July 2003 13:17 > > > To: 'Struts Users Mailing List' > > > Subject: Urgent!!!Sorting Problem while loading > from HashMap > > > > > > > > > Hi > > > I am loading a html:select box with property as > the key in the HashMap( > > ID > > > corresponding to the value which is displayed) > and labelproperty as the > > > value.When i am fetching from the database i am > sorting by the value and > > > then only loading in the HashMap.But when i see > the select box the values > > > are not sorted..which makes my form not so > userfriendly...Kindly help to > > > display sorted when i am loading from a > HashMap...(When i load using an > > > araylist it displays the values in the order i > have stored and there is > > no > > > sorting problem) > > > > > > Thanks in Advance > > > Regds > > > Partha > > -- > Kris Schneider <mailto:[EMAIL PROTECTED]> > D.O.Tech <http://www.dotech.com/> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: > [EMAIL PROTECTED] > For additional commands, e-mail: > [EMAIL PROTECTED] > __________________________________ Do you Yahoo!? SBC Yahoo! DSL - Now only $29.95 per month! http://sbc.yahoo.com --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
