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From "Don Forbes" <>
Subject RE: [lang] Reusable Builder classes
Date Thu, 02 Oct 2003 09:31:39 GMT

Sorry, I took it as a given that excessive object creation was an evil, e.g. Brian Goetz's
JavaWorld article "Design for Performance, Part 2: Reduce Object Creation" (;
see also e.g.,

I do quite a lot of performance-critical work involving large collections of objects.  For
instance, transforming mainframe extracts of several million records into data warehouse load
files.  This may entail using several lookup caches in the form of SortedMaps, HashMaps or
sorted arrays (with binary search) which may themselves contain millions of entries.  We aim
for the complete cache load and transformation to run in minutes rather than hours.

This environment multiplies the effect of bad choices and the effects on run times visibly
punishes things like avoidable object creation.  This is not about milliseconds.

Matt's suggestion makes sense for HashCodeBuilder, it had crossed my mind too.  But it won't
work for CompareToBuilder or EqualsBuilder.  I felt my suggestion was a good compromise with
a consistent approach to all the Builder classes.  I'm familiar with the debate about premature
optimisation but I don't feel that label is really called for here.

I'm not sure that doing an analysis that would satisfy the purists is something I can afford
to do now.  I understand that my requirement is perhaps rather specialised, and at least now
I know where I stand.

When time permits I'll benchmark some options and also count the number of times compareTo()
gets invoked doing sorts etc., and let you know.

Thanks for your interest.


-----Original Message-----
From: Hope, Matthew []
Sent: 01 October 2003 11:56
To: 'Jakarta Commons Users List'
Subject: RE: [lang] Reusable Builder classes

The end user may wish to consider whether their use case would benefit from
caching the calculated value...

If you can handle doing the coding of a dirty flag and its maintenance then
the only overhead is in a boolean, int (and possibly String if you want to
cache toString()) instance variable.

If the data rarely changes and the performance in this area is really what
matters this will provide far more bang for buck than just caching the
Builder Object.

But what everyone else said is the place to start - is this really what's
killing performance, what does profiling tell you?


-----Original Message-----
From: __matthewHawthorne [] 
Sent: 30 September 2003 23:25
To: Jakarta Commons Users List
Subject: Re: [lang] Reusable Builder classes

Another quote I've heard: "premature optimization is the root of all 
evil."  I agree with what you're saying.

With the exception of some common sense situations, I think that 
performance optimizations carry the ability to pollute an API and mangle 
the internal code.  Garbage collection is improving, JVMs are getting 
faster... I'd prefer clean, maintainable code over that which goes to 
extremes to save a few milliseconds.

Measurements are a necessity for this sort of thing.  I think the 
problem has to be proven before the solution is started.  There's a nice 
profiler plugin for Eclipse that I've used a few times, it seems to do 
the job.

Gary Gregory wrote:

> Hi,
> I am always very weary of doing anything in the name of performance 
> without any measurements based on a real usage scenario. Old motto on 
> performance
> improvements: First, don't' do it. Second, think about it, then don't do
> ;-)
> I think it would be interesting to discuss this if/when the post read 
> like: "In our app x, we've measured with JProbe (or whatever) a 
> bottleneck in this and that place were 80% of the time for a set of 
> tasks is spent in FooBuilder.doThisOrThat()."
> There are two kinds of performance: speed and memory usage. Here we 
> are talking about creating code to change the profile and balance of 
> these two aspects based on a hunch. I have been to many performance 
> talks (JavaOne) where one hears things like (paraphrasing): "in an 
> extreme case, we had this customer try such and such performance 
> improvements of caching this and that in memory which effectively 
> negated GC from collecting anything and led to a different kind of 
> memory leak (a.k.a unwanted object retention) and performance 
> degradation due to virtual memory swapping".
> From the POV of client code, this seems like quite a complication to 
> deal with, especially when considering MT issues.
> Without talking sides on the details of this particular issue, when 
> designing an API, you also have to consider what choices you'll give 
> client code. At which point will the client code writer scratch his 
> head with a "there are so many ways of doing the same thing, which one 
> is best and when?". It is best if all of these choices are documented.
> Gary
>>-----Original Message-----
>>From: Stephen Colebourne []
>>Sent: Tuesday, September 30, 2003 13:03
>>To: Jakarta Commons Users List
>>Subject: Re: [lang] Reusable Builder classes
>>Possible I suppose. I guess I don't have strong views either for or 
>>Any other [lang] committers have any views?
>>----- Original Message -----
>>From: "Don Forbes" <>
>>I find the Builder classes really helpful, but find it wasteful having 
>>to create a new HashCodeBuilder, CompareToBuilder or EqualsBuilder for 
>>each invocation of a hashCode, equals or compareTo method.  In some 
>>situations, such as a sort of a large collection, these methods can 
>>end up being called often, thus imposing a high garbage collection 
>>I am thinking of something analogous to StringBuffer, which can be 
>>reset for reuse by simply calling setLength(0).
>>How about a simple reset() method, with no parameters, that just 
>>resets the internal state (e.g. the variable "comparison" in the case 
>>CompareToBuilder) to its initial value?  (Possibly also a getter to 
>>determine whether the builder is currently in a reusable state.)
>>Granted, this would require the Builder to be an instance variable of 
>>the calling object rather than a local variable, thus raising issues 
>>of thread safety.  Unfortunately using sychronized methods has 
>>something of a bad name for performance.  In my understanding and 
>>experience this is an unfair reputation, and my guess is that the 
>>overhead would be amply compensated for
>>by the savings in garbage collection.  But short of this, provided the
>>caller is given the responsibility for synchronising access to the object
>>a multithreading scenario, I don't see a problem.
>>Any thoughts?
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