String & StringBuffer again......

hi all,
after coding for 1 year with java (before c++ for years) i used the stringbuffer class for the first time a few days ago.
i implemented a search which has to do lot's (!) of string operations.
the search was very slow, so i tried stringbuffer.
i replaced and changed all the string stuff into stringbuffer stuff - but the performance was still bad...
so could the following be the problem:
stringbuffer don't know important functions like 'indexof(String)'.
so everytime i need indexof (for example), i do the toString() function...
now my first question:
is all the stringbuffer advantage gone if i use toString() at one or to places ==> how much performance will this cost (in a loop...)?
my second question:
what's faster, deleting the content of an used stringbuffer with delete(int,int) or just creating a new with new stringbuffer(String) ?
thanx a lot,
andi

What you should probably do is use "javap -c" to look at the bytecode produced in your class. Then you can see exactly how many objects are being created for each way of coding the String and StringBuffer operations.
To answer your question about toString(), it creates an extra String object when called, but does not copy the characters. However, if you subsequently change the original StringBuffer, the characters in it will need to be copied. Therefore, calling toString() and then changing the StringBuffer further can have a serious impact on performance.

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Hi,
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It's terrifying indeed...
Here are my results on a IBM ThinkPad PM 1.7 GHz 512 Mb with Windows XP Pro SP2
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(I modified the println line to get double result)
java -version
java version "1.4.2"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2)
Classic VM (build 1.4.2, J2RE 1.4.2 IBM Windows 32 build cn142-20040926 (JIT ena
bled: jitc))
java StringTest 1
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java version "1.5.0_05"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_05-b05)
Java HotSpot(TM) Client VM (build 1.5.0_05-b05, mixed mode)
java StringTest 1
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java -version
java version "1.6.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-beta-b59)
Java HotSpot(TM) Client VM (build 1.6.0-beta-b59, mixed mode, sharing)
java StringTest 1
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String problem again!!

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Ie acts like an object rather then like a primitive?

Not exactly ...
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UPDATE table_case
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That will fix your immediate problem.
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<rant>
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</rant>

Fastest way to access data between String and char[]

Hi all,
I've been programming a small String generator and was curious about the best and fastest way to do so.
I've done it in two ways and now hope you can tell me if there is a "more java version" or fastest way between those two or if I'm totally wrong as some classe in the API already does that.
Here are the codes:
version 1:
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 stringBuffer =null;version 2:
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 char[] alphabetArray = {'a', 'b', 'c', 'd', 'e', 'f',
 'g', 'h', 'i', 'j', 'k', 'l',
 'm', 'n', 'o', 'p', 'q', 'r',
 's', 't', 'u', 'v', 'w', 'x',
 'y', 'z'}
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 for (int i=0; i < 8; i++)
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 stringBuffer =null;Basically, the question is, what is the safest, fastest and more "to the rules" way to access a char in a sequence?
Thanks in advance.
Edited by: airchtit on Jan 22, 2008 6:02 AM

paul.miner wrote:
Better, use a char[] instead of a StringBuffer/StringBuilder, since you seem to know the size of the array in advance.
Although I imagine making "alphabet" a char[] has slightly less overhead than making it a String
1. It's a lot clearer to write it as a String.
2. You can just call toCharArray() on the String to get a char[], instead of writing out each char individually.
3. Or if you're going to be using a plain alphabet, just use (randomNumber + 'a')
And use Random.nextInt()Hello and thx for the answers,
I know I shouldn't put constants in my code, it was just a piece of code done in 1 minute to help a colleague.
Even if it was just a one minute piece of code, I was wondering about the performance problem on large scale calculating, I mean something like a 25 characters word for billions of customers but anyway, once again, the impact should be minimal.
By the way, I didn't know the Random Class (shame on me, I still don't know the whole API) and, I don't understand why I should be using this one more than the Random.Math which is static and thus take a few less memory and is easier to call.
Is it because of the repartition factor?
According to the API, the Random.Math gives (almost) a uniform distribution whether the Random.nextInt() gives a "more random" int.
I

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Hi Folks,
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I take it back. This is whacked. Please take a look at the picture (http://tinypic.com/view/?pic=nygyu0)
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I went to the row template definition and changed the substitution string #PROJECT_NAME# to #PROJ_NAME# to match the query -- and the substitution strings broke again!
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sojourner_jdk wrote:
Hi DarrylBurke,
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How to remove only the last element of spreadsheet string

I use path to string option to store image path into database and while retrieving the string is again converted into path but it gives out an error as the output of array to spreadsheet string gives out a tab at the end which is unable for the IMAQ read file to recognise.but when i use the path of the image directly into IMAQ readfile the image is opened . so how to remove the tab only at the end of output of the spreadsheet string(whose length can vary)? I have also attached my program with this.
Attachments:
retrieve_images_from_DB.vi ‏65 KB
file_path_to_db_(images).vi ‏40 KB
create_table_for_images.vi ‏45 KB

indhu wrote:
> Thanks for your reply!
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Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

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