java202302java学习笔记第十九天-升级学生管理系统9账号密码

 private  static  boolean checkUsername(String username){
        int len=username.length();
        if(len<3||len>15){
            return  false;
        }
        for (int i = 0; i < username.length(); i++) {
            char c=username.charAt(i);
            if(!((c>='a'&&c<='z')||(c>='A'&&c<='Z')||(c>='0'&&c<='9'))) {
                return false;
            }
        }
        //用户满足内容要求
        //不能是纯数字
        int count=0;
        for (int i = 0; i < username.length(); i++) {
            char c = username.charAt(i);
            if (!((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'))) {
                count++;
                break;
            }
        }
        return  count>0;
    }