public final void sample(){
  long sum=_sum.getAndSet(0);
  int count=_count.getAndSet(0);
  if (count != 0)   _value=sum / (double)count;
 else   _value=0;
}

public final void sample ( ) { long sum = _sum . getAndSet ( 0 ) ; int count = _count . getAndSet ( 0 ) ; if ( count != 0 ) _value = sum / ( double ) count ; else _value = 0 ; }
return the probe ' s next sample .
