java姓名脱敏,String类型中间字符使用*替换

 /**
  * 姓名长度
  */
Integer RESULT_NAME_LENGTH =2;

public  String protectedName(String userName){
    userName = userName.trim();
    char[] r = userName.toCharArray();
    String resultName = "";
    if(r.length == RESULT_NAME_LENGTH){
        resultName =  r[0]+"*";
    }
    if (r.length > RESULT_NAME_LENGTH) {
        String star = "";
        for (int i = 0; i < r.length-RESULT_NAME_LENGTH; i++) {
            star=star+"*";
        }
      resultName = r[0]+star+r[r.length-1];
    }
    return resultName;
}