@Override public final void sample(){
  long count=_count.getAndSet(0);
  long time=_time.getAndSet(0);
  if (count == 0)   _value=0;
 else   _value=time / (double)count;
}

@ Override public final void sample ( ) { long count = _count . getAndSet ( 0 ) ; long time = _time . getAndSet ( 0 ) ; if ( count == 0 ) _value = 0 ; else _value = time / ( double ) count ; }
return the probe ' s next sample .
