public static void main(String[] args) {
        String firtstName = enterName("First");
        String secondName = enterName("Second");
        JOptionPane.showMessageDialog(null, String.format("%s + %s = <Въведи нещо>", firtstName, secondName));
    }

    private static String enterName(String type) {
        String name = "";
        boolean isCorrect = false;
        while (!isCorrect) {
            try {
                name = JOptionPane.showInputDialog(null, "Enter " + type + " Name");
                Double.parseDouble(name);
                JOptionPane.showMessageDialog(null, "Try Again");
            } catch (Exception igonred) {
                JOptionPane.showMessageDialog(null, "Correct - " + name);
                isCorrect = true;
            }
        }
        return name;
    }