Sized

[Brian Goetz]

I think you're focusing on another problem.  These things *have* size() 
methods already; I'm trying to capture this in a finer-grained 
interface.  The "size in O(1) time" is a whole orthogonal concern.

On 11/2/2012 6:27 PM, Kevin Bourrillion wrote:
> My mistake: CHM only has to walk through every /segment/ to add up the
> size, and I was thinking of it as actually traversing every element.
>
> In any event. It's undeniably true that there are numerous
> implementations of Collection out there that don't know their size
> without completely iterating themselves. I still say that if there's any
> value in Sized, it lies in making those implementations /not/ implement
> it while others do.
>
>
>
> On Fri, Nov 2, 2012 at 3:22 PM, Brian Goetz <brian.goetz at oracle.com
> <mailto:brian.goetz at oracle.com>> wrote:
>
>         Of course, some collections, like the key set of a
>         ConcurrentHashMap,
>         don't know their size any more than a garden-variety Iterable does.
>
>
>     That's not exactly true.  In the absence of interference from
>     concurrent modification, the key set of a CHM absolutely knows its
>     size.  It's just that in the presence of interference, the reported
>     size may be stale by the time you receive it.
>
>
>
>
> --
> Kevin Bourrillion | Java Librarian | Google, Inc. |kevinb at google.com
> <mailto:kevinb at google.com>
>