Timer in microsec

Question

Hi:
Does anyone know how to measure time in microseconds? The only class I know of is "System" with its method "currentTimeMillis", which give time difference in milliseconds. I need to time a code which runs in less than milliseconds.
Thanks Guys!

Answer 1

>
What are you talking about?!?! 18Hz clock?
The CPU clock runs at gigahertz these days.I know ;)
The
"system clock" is generated by timer interrupts. The
"standard" 10 ms clock is generated because that was a
convention back in the eighties with Unix (which DOS
adopted). Most OSes now have either a 60Hz (16.66 ms
per interval) or 100Hz (10ms per interval) "clock"
granularity.
I've just said that on a Windows 98 PC I observed
that the result of System.currentTimeMillis() was
updated only in alternating 50 and 60 ms steps.
You just should be prepared. Thank you for your
numbers of 10 and 17 ms. They might be useful
for me in the future to explain something.
But those 10 and 17 ms are no more that 5
times finer than 55 ms, of course ;).
However, most OSes are also capable of generating
finer-grained clocks. Windows NT and XP can
programmatically generate a 1 ms clock timer. So can
POSIXy (Linux, Unix, etc.) systems (though
administratve privileges are usually needed because
this is a system-wide change).
Smaller granularities are theoretically possible, but
at a terrible price in system performance (the kernel
would be spending most of its time handling clock
interrupts).
The Thread.sleep() provides very fine granularity. It
really provides ms wait intervals (even on that
Windows 98 PC that I mentioned).
;) By the way, there even was a bug with the Thread.sleep() fuction:
http://developer.java.sun.com/developer/bugParade/bugs/4500388.html