|
No, Java is bad. If you want to minimize short-lived objects,
use C. Nothing faster than short-lived objects living on the
stack.
Being facetious of course ;) maybe...
Doug
David,
So iterators are bad?
:-P
Cheers,
Ed
David Orme wrote:
Re: explosions of inner classes
On Android (and probably other embedded VMs) construction is expensive
and also leads to more GC pauses. Google recommends minimising
architectures that force a lot of short-lived objects.
Just one more data point for the discussion.
-Dave Orme
On Oct 29, 2008 5:30 AM, "Oberhuber, Martin" <Martin.Oberhuber@xxxxxxxxxxxxx>
wrote:
Hi Scott,
to me, Futures and Listeners don't need to
be a contradiction.
What's more interesting to me, is how to deal with
Progress.
When a Progress Monitor already exists for the client,
then
using it makes a lot of sense even if the result is
obtained
asynchronously:
final CBFuture<IFileStore[]>
childrenF = myFileStore.list(myProgress);
childrenF.chain(new
Callback() {
public void onDone(IStatus result) {
if (result.isOK()) {
handleResult(childrenF.get());
}
};
});
I'm using class "CBFuture" as an "enhanced Future" that
allows
registering Callbacks. Using a Callback style of handling
things,
or CBFuture.waitFor() remains up to the client. Note that
I'm
using a "chain()" method to indicate that the Framework/Future
could
allow chaining multiple callbacks such that one is exeucuted
after
the other. Also note how the callback retrieves the result
of
computation from the Future, and not from the callback
itself.
The problems that I have seen with callbacks in our
products
in the past are listed on
http://wiki.eclipse.org/E4/Pervasive_Themes#Becoming_More_Asynchronous
*
Much boilerplate code - Closures would be nice to avoid
explosion
of anonymous inner classes, which could cause
bloat
* Need clarification on what thread and in what context
the
callback will be called
* When debugging, it is very
hard to trace back the flow of
operation across multiple callback
invocations. It can even
make debuging close to impossible unless
some Tracing
functionality for the callbacks is built into the
Framework
(we ended up doing this in our commercial
product).
* Exception handling needs to be clarified. Java6 Future
only
provides Future#isCanceled(), that's not enough since
the
result of an operation might also be an exception.
I'm
introducint "Istatus result" above but that's also
not
optimal.
The synchronous variant needs more verbosity
writing it than
one would expect, because cancellation and errors
(exceptions)
need to be handled, wrapped and potentially re-wrapped
with
Futures:
final CBFuture<IFileStore[]> childrenF =
myFileStore.list(myProgress);
try {
handleResult(childrenF.get());
} catch(CancellationException e)
{
throw new OperationCancelledException(e);
}
catch(ExecutionExeption e) {
throw new CoreException(new
Status(/*.blabla*/));
}
although that could perhaps be
simplified if we declared some
Eclipse specific implementation of
Future which throws the
kinds of Exceptions that we already know (like
CoreException
embedding an Istatus) instead of the JRE's
ExecutionException
that's really alien to our current code.
Cheers, -- Martin Oberhuber, Senior Member of
Technical Staff, Wind River Target Management Project...
_______________________________________________
eclipse-incubator-e4-dev mailing list
eclipse-incuba...
_______________________________________________
eclipse-incubator-e4-dev mailing list
eclipse-incubator-e4-dev@xxxxxxxxxxx
https://dev.eclipse.org/mailman/listinfo/eclipse-incubator-e4-dev
|
