code: @Override
    public IScan getScanByNumUpper(int scanNum) {
      IScan scan = getNum2scan().ceilingEntry(scanNum).getValue();
      if (scan != null) {
        return scan;
      }
      return null;
    }
docs: Scan with the closest Number greater or equal to the provided one is returned.
  
  @param scanNum scan number
  @return Scan or null, if the ScanCollection didn't have any scans with numbers &gt;= than this
  one