Am 23.12.2010 22:24, schrieb Ulf Zibis:
Aren't the explanation comments from my last example clear enough and more
fluently readable?
For clarification:
// collections to iterate and examine containment on
Collection<?> iterate = c1;
Collection<?> contains = c2;
// performance optimization cases
if (c1 instanceof Set) {
// As mere Collection's contains() impl predictably performs worse
// than Set's (< O(N/2)), iterate on c2.
iterate = c2;
contains = c1;
} else if (!(c2 instanceof Set)) {
// Both are mere collections.
int c1size = c1.size();
int c2size = c2.size();
if (c1size == 0 || c2size == 0) {
// At least one collection is empty. Nothing will match.
return true;
} else if (c1size > c2size) {
// 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
