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From Daniel John Debrunner <...@apache.org>
Subject Re: ArrayInputStream and performance
Date Tue, 28 Nov 2006 17:11:26 GMT
Knut Anders Hatlen wrote:
> Daniel John Debrunner <djd@apache.org> writes:
> 
>> Knut Anders Hatlen wrote:
>>> They use a pattern of first copying the instance
>>> variables into local variables, then do the work on the local
>>> variables, and finally write back to the instance variables. While I
>>> find that a little confusing because I would expect the run-time
>>> compiler to be able to perform that kind of optimization itself,
>>> that's a different issue from what is discussed in this thread.
>> Can the run-time optimizer/compiler perform such an optimization when
>> the instance variable is not final? I would have thought not.
> 
> Yes, I believe it can. Java's memory model basically allows the
> compiler to assume that the variables are accessed by a single thread
> as long as it doesn't hit a memory barrier (like a volatile variable
> or a synchronized block).

How effective can this be when the accesses to the instance field are 
intermixed with method calls of other objects, especially when those 
methods are interface calls?

Dan.



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