1. /**
    2.      * 生成指定位数的随机字符串
    3.      *
    4.      * @param n 位数
    5.      * @return 含大小写字符的字符串
    6.      */
    7. public static String generateNonceStr(int n) {
    8.     // 字符数组
    9.     char[] nonceChars = new char[n];
    10.     // 随机字符的备选值
    11.     String allStr = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    12.     Random r = new Random(); //定义随机数
    13.     for (int i = 0; i < nonceChars.length; ++i) {
    14.         int index = r.nextInt(allStr.length());  //字符长度内选一个随机数值
    15.         nonceChars[i] = allStr.charAt(index);   //随机取1个字符
    16.     }
    17.     return new String(nonceChars);  //返回字符串
    18. }