Re: A good representation of XML in Java?

From:
=?windows-1252?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>
Newsgroups:
comp.lang.java.programmer
Date:
Sun, 19 Sep 2010 22:18:59 -0400
Message-ID:
<4c96c494$0$50450$14726298@news.sunsite.dk>
On 11-09-2010 20:00, Spud wrote:

On 9/7/2010 3:26 PM, Daniel Pitts wrote:

On 9/7/2010 10:27 AM, Spud wrote:

On strings: when you're doing (very) large scale data processing,
strings are a no-no. The only answer is to have some kind of reusable
buffer for storing text.

Define very large scale? Also, "strings" are not the same as "Strings",
so lets make sure you are specifically talking about "using String
instances is a no-no".

Here's a discussion of the topic:

http://lingpipe-blog.com/2010/06/22/the-unbearable-heaviness-jav-strings/


All this says is that there is a 60 byte overhead per String instance.
You're original objection was that it had something to do with bogging
down the GC.

While 60 byte overhead seems to be a lot, keep in mind that any object
holding string-like data will have the same overhead. Reusable objects
(char buffers) may interfere with the GC more than short lived objects,
depending on the GC implementation. I've heard this is the case for most
modern JVM GCs, which is why Object pools are not common in modern Java
programs.

It sounds to me like you read in a few places about potential
inefficiencies with Java Strings, and have decided to avoid them before
finding actual, practical problems.


No. It's based on actual experience, the same experience the blogger had.


Actually if you bother to read the the blog, then the blogger
did not have such experience he just claimed without any evidence
that "It?s just too expensive to allocate objects in tight loops".

And serious research in the topic directly contradicts it.

Brian Goetz in
http://www.ibm.com/developerworks/java/library/j-jtp01274.html

Joshua Bloch Effective Java 1st Ed Item 4 final remarks

One large reusable buffer, containing many strings, is far more
efficient than creating and destroying String objects millions of times
over. Simply have a large array of char, and two parallel arrays of int
that contain pointers to the start and end of each string. This doesn't
work for every app, but it does for this one. Once you've filled the
buffer, processed your batch of strings, and no longer need them, just
reset the pointers and you're done. Zero GC required.


You can't read a blog text correct and you want us to believe
you can measure performance?

Arne

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