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]
