good point. I'll have to review the code in more
detail.
--- Dain Sundstrom <[EMAIL PROTECTED]> wrote:
> Hiram,
>
> This type of construct creates some trick code. You
> iterate over the
> keys, and I assume somewhere in the code you do
> clients.get(key). Well
> there is no guarantee the the key is associated. I
> bet there are a ton
> of other issues as your iterator in the read phase
> drifts from reality
> of changing clients HashMap. Anyway, I hope you
> documented this
> heavily.
>
> -dain
>
> On Thursday, February 13, 2003, at 12:28 PM, Hiram
> Chirino wrote:
>
> > Yep.. your way is valid too but you take a
> > synchronization hit on every read. The otherway,
> the
> > performace hit is on the write. As I said
> previously,
> > if you read the map ALLOT more than you write to
> it,
> > then it makes sense to do it backwards.
> >
> > Regards,
> > Hiram
> >
> > --- Dain Sundstrom <[EMAIL PROTECTED]> wrote:
> >> This seems backwards to me. I usually do
> something
> >> like this:
> >>
> >> class X
> >> {
> >> HashMap clients = new HashMap();
> >>
> >> public void someMethod()
> >> {
> >> synchronized(clients)
> >> {
> >> m.put(dc, cq);
> >> }
> >> ...
> >> }
> >> public void someOtherMethod()
> >> {
> >> HashMap clientsCopy = null;
> >> synchronized(clients)
> >> {
> >> clientsCopy = new HashMap(clients);
> >> }
> >> Iterator i =
> >> clientsCopy.keySet().iterator();
> >> while( i.hasNext() )
> >> {
> >> ...
> >> }
> >> }
> >> }
> >>
> >> For the insert, you only get a quick synchronized
> >> around the add, and
> >> on iteration you get a single copy in the
> >> synchronize. If the
> >> iteration very small and quick, I sometimes put
> the
> >> entire iteration in
> >> the synchronized block, but you need to be
> careful
> >> about open calls.
> >>
> >> -dain
> >>
> >> On Thursday, February 13, 2003, at 11:20 AM,
> Scott M
> >> Stark wrote:
> >>
> >>> I have seen this usage construct in a few places
> >> in the code and it
> >>> makes
> >>> no sense to me:
> >>>
> >>> class X
> >>> {
> >>> HashMap clients = new HashMap();
> >>>
> >>> public void someMethod()
> >>> {
> >>> synchronized(clients)
> >>> {
> >>> HashMap m = new HashMap(clients);
> >>> m.put(dc, cq);
> >>> clients=m;
> >>> }
> >>> ...
> >>> }
> >>> public void someOtherMethod()
> >>> {
> >>> Iterator i =
> clients.keySet().iterator();
> >>> while( i.hasNext() )
> >>> {
> >>> ...
> >>> }
> >>> }
> >>> }
> >>>
> >>> The unsynchronized clients HashMap is
> synchronized
> >> and copied when
> >>> modified and accessed without synchronization in
> >> other contexts. This
> >>> is
> >>> not thread safe for the accesses and makes for
> >> very expensive updates.
> >>> Why isn't the HashMap simply synchronized and
> used
> >> without copying?
> >>>
> >>> xxxxxxxxxxxxxxxxxxxxxxxx
> >>> Scott Stark
> >>> Chief Technology Officer
> >>> JBoss Group, LLC
> >>> xxxxxxxxxxxxxxxxxxxxxxxx
> >>>
> >>>
> >>>
> >>
> >
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