>> Imagine a List class with a "length()" method. The first time the >> length() method is called it walks the list and then stores the size >> internally to a variable so that future calls to length() return this >> size. >> The data model hasn't changed, but the actual implementation state data >> has. >> This could possibly be not thread-safe. >> XML trees are much more complex than this. > > ... and that's exactly what the NodeLists do in Xerces' DOM implementation > for length(). Also, each time you call item() it stores the index and last > Node returned, so that when you access n+1, it only needs to walk to the > next sibling to return the result. Without that optimization the time spent > iterating over the NodeList would be O(n^2) instead of linear.
Ah ok, so there is some saved state going on. Next question, what makes iterating over the list n-squared? thanks -- Andrew Welch http://andrewjwelch.com --------------------------------------------------------------------- To unsubscribe, e-mail: j-users-unsubscr...@xerces.apache.org For additional commands, e-mail: j-users-h...@xerces.apache.org
