生成固定长度的随机字符和数字

 /**
     * 生成固定长度的随机字符和数字
     * @param len
     * @return
     */
	
    public static String GetRandomCharAndNumber(int len) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i <len; i++) {
            int intRand = (int) (Math.random() * 52);
            int numValue = (int) (Math.random() * 10);
            char base = (intRand < 26) ? 'A' : 'a';
            char c = (char) (base + intRand % 26);
            if(numValue%2==0){
                sb.append(c);
            }else{
                sb.append(numValue);
            }
        }
        return sb.toString();
    }