Ulf, a previous email by Remi said only to invoke size() if the collection
is a Set.
Paul
On Thu, Dec 23, 2010 at 4:24 PM, Ulf Zibis <ulf.zi...@gmx.de> wrote:
> Am 23.12.2010 22:24, schrieb Ulf Zibis:
>
>> Aren't the explanation comments from my last example clear enough and more
>> fluently readable?
>>
>
> Shouldn't we examine the size at first? :
>
>
> // collections to iterate and examine containment on
> Collection<?> iterate = c1;
> Collection<?> contains = c2;
>
> // performance optimization cases
> int c1size = c1.size();
> int c2size = c2.size();
> if (c1size == 0 || c2size == 0) {
> // At least one collection is empty. Nothing will match.
> return true;
> if (c1 instanceof Set || (!(c2 instanceof Set) && c1size > c2size) {
>
> // As mere Collection's contains() impl predictably performs
> worse
> // than Set's (< O(N/2)), iterate on c2.
> // Or if both are mere collections, iterate over smaller
> collection.
>
> // E.g. if c1 contains 3 elements and c2 contains 50 elements
> and
> // assuming contains() requires ceiling O(N/2) comparisons then
> // checking for all c1 elements in c2 would require 75
> comparisons
> // vs. all c2 elements in c1 would require 100.
> iterate = c2;
> contains = c1;
> }
>
> -Ulf
>
>
>
