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Re: difference between hashtable and hashMap ?

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In article <a32f3a08-49ca-48dc-88c6-1b58aacbf1e5@googlegroups.com>, 
Rishipal Singh (95rishipal@gmail.com) says...
> 
> what is difference between hashtable and hashMap ;
>  please explain with examples

The HashTable is synchronized (not including the iterator), which is not 
needed usually. 
If you need synchronization you can use 
Map<K,V> synchMap = Collections.sychronizedMap(unsynchMap);
to wrap any map in a decorator/proxy map that adds synchronization (and 
is backed by the original you provided). One might think that with this 
the original HashTable is not needed anymore, but that's not entirely 
true.

The major advantage of java.util.HashTable to java.util.HashMap is that 
you can have a custom load factor with the HashTable, which might help 
you in improving the behavior in cases where you need to sacrifice some 
speed in favor of space. 
An increased load factor will slow the table down as hash collisions get 
more likely, but the table will not grow in size that fast, OTOH a lower 
load factor will make the table grow faster to provide more space for 
less hash collisions. 

Usually the load factor is a non issue and synchronization is not 
needed, which means that HashMap should be your standard map 
implementation. In rare cases, if you really need to fine tune a map, wi 
ch means you need some special property that HashMap doesn't supply 
(altering the load factor, iterating in the order in that the elements 
were added, removing duplicates and/or ordering according to a custom 
comparator stragety, lightly multithreaded access, heavy multithreaded 
access, values that become free for garbage collection if their keys are 
not referenced anymore, etc.) you might have a look at other Map 
implementations, such as HashTable, ConcurrentHashMap, TreeMap or 
WeakHashMap. But you should really know what you're doing there, which 
means (regarding your novice question), probably not yet.

Kind regards,
Wanja

-- 
..Alesi's problem was that the back of the car was jumping up and down 
dangerously - and I can assure you from having been teammate to 
Jean Alesi and knowing what kind of cars that he can pull up with, 
when Jean Alesi says that a car is dangerous - it is. [Jonathan Palmer]

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difference between hashtable and hashMap ? Rishipal Singh <95rishipal@gmail.com> - 2014-08-23 23:03 -0700
  Re: difference between hashtable and hashMap ? Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-24 08:09 +0000
  Re: difference between hashtable and hashMap ? Josip Almasi <joe@vrspace.org> - 2014-08-24 11:41 +0200
  Re: difference between hashtable and hashMap ? Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-08-24 08:13 -0400
    Re: difference between hashtable and hashMap ? Arne Vajhøj <arne@vajhoej.dk> - 2014-08-24 08:48 -0400
      Re: difference between hashtable and hashMap ? Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-08-24 09:28 -0400
        Re: difference between hashtable and hashMap ? Arne Vajhøj <arne@vajhoej.dk> - 2014-08-24 14:31 -0400
          Re: difference between hashtable and hashMap ? Roedy Green <see_website@mindprod.com.invalid> - 2014-08-24 22:35 -0700
            Re: difference between hashtable and hashMap ? Arne Vajhøj <arne@vajhoej.dk> - 2014-08-25 20:41 -0400
            Re: difference between hashtable and hashMap ? Jeff Higgins <jeff@invalid.invalid> - 2014-08-26 04:21 -0400
          Re: difference between hashtable and hashMap ? "Qu0ll" <Qu0llSixFour@gmail.com> - 2014-08-31 10:27 +1000
            Re: difference between hashtable and hashMap ? Arne Vajhøj <arne@vajhoej.dk> - 2014-09-07 22:10 -0400
              Re: difference between hashtable and hashMap ? "Qu0ll" <Qu0llSixFour@gmail.com> - 2014-09-08 13:41 +1000
  Re: difference between hashtable and hashMap ? Arne Vajhøj <arne@vajhoej.dk> - 2014-08-24 08:52 -0400
    OT: Re: difference between hashtable and hashMap ? Wayne <nospam@all.invalid> - 2014-08-24 18:04 -0400
  Re: difference between hashtable and hashMap ? Roedy Green <see_website@mindprod.com.invalid> - 2014-08-24 22:36 -0700
  Re: difference between hashtable and hashMap ? Brixomatic <brixomatic@yahoo.com> - 2014-08-30 14:07 +0200
    Re: difference between hashtable and hashMap ? Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-08-30 16:39 -0400
      Re: difference between hashtable and hashMap ? Brixomatic <brixomatic@yahoo.com> - 2014-08-31 09:42 +0200

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