problems with times

[ALi]

Hello i have problems with times in generating pdf
I want to know why the times are so different between one invocation and two


for example i have the class makePDF

main () {
   time1
   makePDF(xml,xsl);
   time2
   println(time2-time1)
}
the times are over 8 seconds
more or less (with my xsl)

if i have
main () {
for (1-10) {
   time1
   makePDF(xml,xsl);
   time2
   println(time2-time1)
}
}

the first time is 8 seconds, but the seconds ones are less but much less
the second is 3 seconds the third 1500 miliseconds and after over 300 miliseconds .....
why is these? is it because the fop need to compile the xsl? Are any form to force to cache the compilation of xsl? (in order to always take the same time.

We have different xsl and one class that makes alls


thx for your help