数字前面加*

private static void markNum(String str) {
    StringBuilder result = new StringBuilder();
    boolean isFrist = true;
    for (char c : str.toCharArray()) {
        boolean isNum = ‘0‘ <= c && ‘9‘ >= c;
        if(isNum && isFrist){
            result.append("*").append(c);
            isFrist = false;
        }else {
            result.append(c);
            if(!isNum){
                isFrist = true;
            }

        }
    }

    System.out.println(result);
}