benefits of Collections.synchronizedMap(new HashMap()) over Hashtable


hi

this is our EJBHomeFactory class ;we have implemented singleton pattern for this;
my doubt is

 synchronizing the hashmap  using Collections.synchronizedMap ,

 i can achieve this functionality using Hashtable also;

like this
Hastable ht = new Hastable();

by default hashtable gives synchronization; why they have written Collections.synchronizedMap(new HashMap());

whta benefits will it give?

 homes       =       Collections.synchronizedMap(new HashMap());

public class EJBHomeFactory
{
  private Map         homes;
  private static  EJBHomeFactory singleton;
  private Context ctx;

  private EJBHomeFactory() throws NamingException
  {
          homes       =       Collections.synchronizedMap(new HashMap());
          ctx       =       new InitialContext();

  }

  public static EJBHomeFactory getInstance() throws NamingException
  {
      if (singleton == null)
      {
        singleton = new EJBHomeFactory();
      }
    return singleton;
  }
}
LVL 20
chaitu chaituAsked:
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petmagdyCommented:
>>  homes      =      Collections.synchronizedMap(new HashMap());
Returns a synchronized (thread-safe) map backed by the specified map. In order to guarantee serial access, it is critical that all access to the backing map is accomplished through the returned map.

which means saftly more than one thread can update/read ur hashtable
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objectsCommented:
Its there if you want a synchronized Map that uses a *different* Map implementation, such as HashMap.
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chaitu chaituAuthor Commented:
i have another doubt

class EJBHomeFactory  is itself  is a singleton meena only single instance at a time is possible;

again why we r making making map as synchronized

using this:
 homes      =      Collections.synchronizedMap(new HashMap());


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objectsCommented:
singleton and synchronized are not really related.
Singltons still need to be correctly synchronized if access by mutiple threads.
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objectsCommented:
> Returns a synchronized (thread-safe) map backed by the specified map.

But you get that already with a Hashtable.
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