随机3位ascii码

1. 利用大小写字母和数字生成范围内不重复的3位字符串

　　public void getTargetNo() {
        final String WORD = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
        final int BASE = WORD.length();
        int increaseId = 0;// 增长的序列
        int div = increaseId;
        StringBuffer sb = new StringBuffer();
        while (div > 0) {
            int surplus = div % BASE;
            div = div / BASE;
            sb.append(WORD.charAt(surplus));
        }
        String target = sb.append("000").reverse().toString();
        target = target.substring(target.length() - 3, target.length());
        System.out.println(target);
    }