特殊字符乱码解决思路，直接使用ASCII码对照表解决

int symbol =  42;
System.out.println(symbol+":"+(char)symbol);

附：ASCII编码对照表网站：http://ascii.911cha/?year=12

/**
 * 随机生成times长度的验证码
 * @param times
 * @return
 */
private static String randomGenerateVertifivationCode(int times) {
    String ret = "";
    for (int i = 0; i < times; i++) {
        int intVal = (int) (Math.random() * 26 + 97);
        ret += (char)intVal;
    }
    return ret;
}