Re: synchronized HashMap vs. HashTable
Mikhail Teterin wrote:
I need multiple threads to be able to operate on the same Map. The
HashMap's
documentation at
http://java.sun.com/javase/6/docs/api/java/util/HashMap.html
advises the following construct:
Map m = Collections.synchronizedMap(new HashMap(...));
However, the HashTable is, supposedly, inherently thread-safe.
That is not true. Hashtable was never claimed to be inherently thread-safe.
It is not inherently thread-safe. Its methods are synchronized.
HashMap.
I saw somewhere, that HashTable is a "legacy" class -- is that true?
Yes.
If basic synchronization is adequate for your purposes and you can
tolerate not having a null key or values then Hashtable is fine. If you
Unless you need total thread safety, in which case you need more than what
Hashtable or Collections.synchronizedMap() provide.
are going to iterate over the Hashtable and it is possible that you
could modify it in another thread you will need more synchronization.
Or if you do check-and-set.
This is the exact same consideration in Collections.synchronizedMap().
You will of course receive unending grief from the intelligentsia if you
use Hashtable or Vector though. I just ignore them.
Here's why the "intelligentsia" (thanks for the compliment, btw) object to
Hashtable - it has features you don't want or need. Use HashMap or another
Map implementation, not Hashtable, which is a clean member of the collections
framework.
The question isn't can you use Hashtable, but why would you? HashMap has the
full panoply of collections-framework capabilities and no extraneous warts.
Use HashMap.
Same argument for Vector vs. ArrayList.
--
Lew