java - 罗马数字和正则表达式

我正在开发一个确定输入的字符串是罗马数字的程序。我的问题是在以下代码中

    public void romancheck(String num){
    if(num.isEmpty()){
        JOptionPane.showMessageDialog(null, "No number typed");
    }
    if (num.matches("[IVXLCDM]+")){
        repeatefinder(num);
       if(repeated == 'I' || repeated == 'V' || repeated == 'X' || repeated == 'L' || repeated == 'C' || repeated == 'D' || repeated == 'M'){
        JOptionPane.showMessageDialog(null, repeated + " is repeated more than three times in " + num);
       }
       else{
           JOptionPane.showMessageDialog(null, num + " is a roman number");
       }
    }
    if(){
        JOptionPane.showMessageDialog(null,  + " is not a roman number in " + num);
}
}

我使用正则表达式num.matches("[IVXLCDM]+")来确定输入的字符串是否仅包含罗马数字字符。我的问题是，如果要使用最后一个if语句，如果字符串中的字符不是罗马数字字符，我想打印一条消息。在字符串中查找不是罗马数字字符的字符的最有效方法是什么？

最佳答案

找到第一次出现

else {
    Matcher matcher = Pattern.compile("[^IVXLCDM]").matcher();
    matcher.find();
    JOptionPane.showMessageDialog(null, matcher.group() + " is not a roman number in " + num);
}

找到所有出现的地方

else {
    JOptionPane.showMessageDialog(null, num.replaceAll("[^IVXLCDM]", "") + " are not roman numbers in " + num);
}