How to measure and control process CPU time of a java program

Question

Hi dudes,
what I am trying to do is to compare 2 algorithms, with the same computation time. To measure the time, one can for example:
long startTime = System.currentTimeMillis();
while (System.currentTimeMillis() - startTime < 10 * 1000) {
running some code
However, in this case System.currentTimeMillis() measures only the wall clock time, not the real process time, i.e. if the CPU is also running some other processes at the same time, the computation time measure is inaccurate.
I learned from other post that this is not easy, but is there on earth a way to solve it? the java profiler seems to be able to monitor the process time but cannot be used to control the computation time at run time. And another thing I learned is a method Thread.getCurrentThreadCpuTime, does it measure the real thread process time or wall clock time?
Any other suggestions? I had all my codes in java and used only single thread, running under linux.
Thanks a lot in advance!
Eric

Answer 1

Check out:
http://java.sun.com/javase/6/docs/api/java/lang/management/ThreadMXBean.html
The timing methods measure thread CPU time, not wall clock time.