Hmmm.. Using jdk1.4 under windows 2000 I got the error message:
not a statement: String a = "aa";
Declarign a String a; and changing the String a = "aa"; to a += "aa"; it worked but,
despite my predictions, the first chunk of code run faster than the second! I would
expect the second to be faster... After running the program twice doing a
+= "aa", the first loop yielded 45396 and 45075 respectively while the second loop
+yeilded 46486 and 45255.
Weird. Since the first loop has the overhead of recalculating the arary length (even
if it is a minimum overhead calculation) I would expect different results...
14/12/2001 10:58:23, ShriKant Vashishtha <[EMAIL PROTECTED]> wrote:
>Hi,
>
>This is the actual code which I tested. I am using the IBM WebSphere3.53
>JIT
>enabled compiler. In my view also the second code should have been faster.
>But
>it's the first code instead which is puzzling me.
>
>-ShriKant
>
>
>
>A mailing list about Java Server Pages specification and reference wrote:
>
>> From: Sujit <[EMAIL PROTECTED]>@JAVA.SUN.COM on 12/14/2001 05:35 AM EST
>>
>> Please respond to A mailing list about Java Server Pages specification
>and
>> reference <[EMAIL PROTECTED]>
>>
>> To: [EMAIL PROTECTED]
>> cc:
>> Subject: Re: OffBeat question...Java performance.
>>
>> Is this the actual code you tested and got the output ...
>> or
>> instead of the line String a = "aa";
>> you had some other code ??
>>
>> actually, String a = "aa"; even if you loop does nothing ...
>>
>> I think both the for loop will not be executed at all ...
>>
>> the JVM should optimises the code ...
>> and the time should be same ...
>>
>> BTW your second code snippet should be faster than the first one ...
>>
>> ----- Original Message -----
>> From: "ShriKant Vashishtha" <[EMAIL PROTECTED]>
>> To: <[EMAIL PROTECTED]>
>> Sent: Friday, December 14, 2001 5:14 AM
>> Subject: Re: OffBeat question...Java performance.
>>
>> > Hi,
>> >
>> > I apologise for the mistake. You are right. Please find the currect
>> > snippets.
>> >
>> > String [] arrayStr = new String[20000];
>> > System.out.println(System.currentTimeMillis());
>> > for(i=0;i<arrayStr.length;i++){
>> > String a="aa";
>> > }
>> > System.out.println(System.currentTimeMillis());
>> >
>> > Output:
>> > 1008319728796
>> > 1008319728799
>> >
>> > String [] arrayStr = new String[20000];
>> > int length = arrayStr.length;
>> > System.out.println(System.currentTimeMillis());
>> > for(i=0;i<length;i++){
>> > String a="aa";
>> > }
>> > System.out.println(System.currentTimeMillis());
>> >
>> > Output:
>> > 1008319767200
>> > 1008319767221
>> >
>> > Regards,
>> > -ShriKant
>> >
>> > A mailing list about Java Server Pages specification and reference
>wrote:
>> >
>> > > From: Sujit <[EMAIL PROTECTED]>@JAVA.SUN.COM on 12/14/2001 04:51 AM
>> EST
>> > >
>> > > Please respond to A mailing list about Java Server Pages
>specification
>> > and
>> > > reference <[EMAIL PROTECTED]>
>> > >
>> > > To: [EMAIL PROTECTED]
>> > > cc:
>> > > Subject: Re: OffBeat question...Java performance.
>> > >
>> > > what is the difference between both the code ..
>> > >
>> > > I don't see any difference between the code
>> > > that is embedded between the system.out's
>> > >
>> > > am I missing something ??
>> > >
>> > > ----- Original Message -----
>> > > From: "ShriKant Vashishtha" <[EMAIL PROTECTED]>
>> > > To: <[EMAIL PROTECTED]>
>> > > Sent: Friday, December 14, 2001 4:34 AM
>> > > Subject: OffBeat question...Java performance.
>> > >
>> > > > Hi,
>> > > >
>> > > > I am trying to judge the performance impact of the following Java
>> code.
>> > > >
>> > > > String [] arrayStr = new String[20000];
>> > > > System.out.println(System.currentTimeMillis());
>> > > > for(i=0;i<arrayStr.length;i++){
>> > > > String a="aa";
>> > > > }
>> > > > System.out.println(System.currentTimeMillis());
>> > > >
>> > > > Output:
>> > > > 1008319728796
>> > > > 1008319728799
>> > > >
>> > > > String [] arrayStr = new String[20000];
>> > > > int length = arrayStr.length;
>> > > > System.out.println(System.currentTimeMillis());
>> > > > for(i=0;i<arrayStr.length;i++){
>> > > > String a="aa";
>> > > > }
>> > > > System.out.println(System.currentTimeMillis());
>> > > >
>> > > > Output:
>> > > > 1008319767200
>> > > > 1008319767221
>> > > >
>> > > > In my view the first code stub should have been faster as in the
>> second
>> > > > snippet we are getting an overhead of a instance variable call over
>> an
>> > > > String [] object compared to the length already computed in the
>first
>> > > > one. What is happening behind the scene, I am not aware. Could
>> somebody
>> > > > please explain.
>> > > >
>> > > > Thanks,
>> > > > -ShriKant
>> > > >
>> > > >
>> > >
>> >
>>
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__________________________________________
"It can only be attributed to human error"
2001 A Space Odyssey
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