docs: public double getDouble(int columnIndex) {
  		Object fieldValue = data[columnIndex];
  		if (fieldValue == null) {
  			return 0.0;
  		}
  		if (fieldValue instanceof Number) {
  			return ((Number) fieldValue).doubleValue();
  		}
  		throw new DBFException("Unsupported type for Number at column:" + columnIndex + " "
  				+ fieldValue.getClass().getCanonicalName());
  	}