java查找字符串中某字符第n次出现的索引

    public static int getIndexOf(String data,String str,int num){
        Pattern pattern = Pattern.compile(str);
        Matcher findMatcher = pattern.matcher(data);
        //标记遍历字符串的位置
        int indexNum=0;
        while(findMatcher.find()) {
            indexNum++;
            if(indexNum==num){
                break;
            }
        }
        return findMatcher.start();
    }