On Jun 10, 2008, at 09:54, Max Berger wrote:
as far as I can tell, there where two issues with my cleanups
yesterday: Readablility and Performance.
I've just submitted a patch which adds a "ListUtil" class, to make
the code more readable again. I've replaced (hopefully) all
occurrences of size() - 1 with the call to these utils. Since they
are static the hotspot engine will pick them up and inline them
very nicely, so there should be no performance overhead.
I hope this addresses the readability issue.
Performance of list.get(list.size()-1). In the default
implementation of LinkedList ( sun jdk), there is no performance
penalty for this call. The list is linked from both ends, and all
calls to an element > size()/2 are searched from the back. There is
a small overhead, since we now have two virtual method calls
instead of one, again something that hotspot can iron out very nicely.
Also: Calls to interface methods are not slower than calls to the
class directly: In both cases the virtual method table is
consulted, as class methods are overridable. The only exception is
if the class method or the class is declared final: Then the
compiler may optimize the calls.
OK, that takes care of that. Seems I'm still stuck with some ideas on
pre-HotSpot VMs... Thanks for investigating this!
I've also noted:
There are a lot of list.size() > 0 calls. I've replaced the ones in
the touched files with .isEmpty(), which is more performant.
That's one I usually replace myself too, if I encounter it.
Definitely no argument from me there.
Cheers
Andreas
