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.



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