code: protected void validateEqualField(String field_1, String field_2, String errorKey, String errorMessage) {
  		String value_1 = controller.getPara(field_1);
  		String value_2 = controller.getPara(field_2);
  		if (value_1 == null || value_2 == null || (! value_1.equals(value_2))) {
  			addError(errorKey, errorMessage);
  		}
  	}
docs: Validate equal field. Usually validate password and password again