code: public Double getDouble(final int index) {
      if (_values[index] == null || _values[index].isEmpty()) {
        return null;
      } else {
        return Double.parseDouble(_values[index]);
      }
    }
docs: Returns an entry from a given column index as a Double (possibly null). Throws as ArrayIndexOutOfBoundsException if the index is
  greater than the number of columns in the header definition. Throws a NumberFormatException if the underlying data can not be parsed as
  a double precision floating point number.
  
  @param index the index of the entry, zero-based
  @return the value or null if the value is null or empty