code: import java.lang.management.ManagementFactory;
  import java.lang.management.ThreadMXBean;
  
  public class TimeIt {
  	public static void main(String[] args) {
  		final ThreadMXBean threadMX = ManagementFactory.getThreadMXBean();
  		assert threadMX.isCurrentThreadCpuTimeSupported();
  		threadMX.setThreadCpuTimeEnabled(true);
  		
  		long start, end;
  		start = threadMX.getCurrentThreadCpuTime();
  		countTo(100000000);
  		end = threadMX.getCurrentThreadCpuTime();
  		System.out.println("Counting to 100000000 takes "+(end-start)/1000000+"ms");
  		start = threadMX.getCurrentThreadCpuTime();
  		countTo(1000000000L);
  		end = threadMX.getCurrentThreadCpuTime();
  		System.out.println("Counting to 1000000000 takes "+(end-start)/1000000+"ms");
  
  	}
  
  	public static void countTo(long x){
  		System.out.println("Counting...");
  		for(long i=0;i<x;i++);
  		System.out.println("Done!");
  	}
  }
  