Both provide key-value access to data. The Hashtable is one 
of the original collection classes in Java. HashMap is part 
of the new Collections Framework, added with Java 2, v1.2.
The key difference between the two is that access to the 
Hashtable is synchronized on the table while access to the 
HashMap isn't. You can add it, but it isn't there by 
default.

Another difference is that iterator in the HashMap is fail-
safe while the enumerator for the Hashtable isn't. If you 
change the map while iterating, you'll know.

And, a third difference is that HashMap permits null values 
in it, while Hashtable doesn't. 

For new code, I would tend to always use HashMap.

Both provide key-value access to data. The Hashtable is one 
of the original collection classes in Java. HashMap is part 
of the new Collections Framework, added with Java 2, v1.2.
The key difference between the two is that access to the 
Hashtable is synchronized on the table while access to the 
HashMap isn't. You can add it, but it isn't there by 
default.

Another difference is that iterator in the HashMap is fail-
safe while the enumerator for the Hashtable isn't. If you 
change the map while iterating, you'll know.

And, a third difference is that HashMap permits null values 
in it, while Hashtable doesn't. 

For new code, I would tend to always use HashMap.

Yes... I agree with u khalid.
can u send the examples in CFW.
Thanks in Advance.