docs: public String getString(int columnIndex) {
  		if (columnIndex < 0 || columnIndex >= data.length) {
  			throw new IllegalArgumentException("Invalid index field: (" + columnIndex+"). Valid range is 0 to " + (data.length - 1));			
  		}
  		Object fieldValue = data[columnIndex];
  		if (fieldValue == null) {
  			return null;
  		}
  		if (fieldValue instanceof String) {
  			return (String) fieldValue;
  		}
  		return fieldValue.toString();
  	}