private List<JTextComponent> validationFields;
private List<JLabel> errorLabels;

private void initValidation() {
	validationFields = Arrays.asList();
	errorLabels = Arrays.asList();
}

private void hideErrors() {
	errorLabels.forEach(e -> e.setVisible(false));
}

private boolean formValid() {
	hideErrors();
	boolean ok = true;
	for (int i = 0; i < validationFields.size(); i++) {
		ok &= !validationFields.get(i).getText().isBlank(); 
		errorLabels.get(i).setVisible(validationFields.get(i).getText().isBlank());
		if ("Double".equals(validationFields.get(i).getName())) {
			try {
				Double.valueOf(validationFields.get(i).getText().trim());
			} catch (NumberFormatException e) {
				errorLabels.get(i).setVisible(true);
				ok = false;
			}
		}
	}
	return ok;
}