@Override public final void sample(){
  long totalCount=_totalCount.get();
  long lastTotal=_lastTotal;
  _lastTotal=totalCount;
  _value=totalCount - lastTotal;
}

@ Override public final void sample ( ) { long totalCount = _totalCount . get ( ) ; long lastTotal = _lastTotal ; _lastTotal = totalCount ; _value = totalCount - lastTotal ; }
sample the total count
