java base64

	  public static String decode(String str62) {
	        String[] ss = split(str62, 4);
	        StringBuilder sb = null;
	        for (String s : ss) {
	            s = toDecString(s);
	            if (sb == null) {
	                sb = new StringBuilder(s);
	            } else {
	                sb.append(format(s, 7));
	            }
	        }
	        return sb.toString();
	    }


		private static String format(String str, int len) {
	        if (len <= str.length()) {
	            return str;
	        }
	        char[] cs = new char[len];
	        Arrays.fill(cs, '0');
	        return String.copyValueOf(cs, 0, len - str.length()) + str;
	    }

	    private static String toDecString(String str62) {
	        long res = 0;
	        int len = str62.length();
	        for (int ii = 0; ii < len; ii++) {
	            long atom = (long) Math.pow(62, len - ii - 1);
	            res = res + atom * convert2Int(str62.charAt(ii));
	        }
	        return String.valueOf(res);
	    }


	    private static int convert2Int(char c) {
	        if (c >= 48 && c <= 57) {//0-9
	            return c - 48;
	        } else if (c >= 97 && c <= 122) {//a-z
	            return c - 87;
	        } else if (c >= 65 && c <= 90) {//A-Z
	            return c - 29;
	        } else {//不支持的字符
	            return -1;
	        }
	    }
	    
	    private static String[] split(String s, int len) {
	        int count = s.length();
	        int nn = count % len;
	        int size = (nn > 0) ? count / len + 1 : count / len;
	        String[] res = new String[size];
	        nn = nn > 0 ? nn : len;
	        res[0] = s.substring(0, nn);
	        for (int ii = 1; ii < size; ii++) {
	            res[ii] = s.substring((ii - 1) * len + nn, ii * len + nn);
	        }
	        return res;
	    }
	    
	    public static void main(String[] args) {
			 Test test = new Test();
			 //http://weibo.com/3173644855/zDl0ZAVZC
			 String s=test.decode("zDl0ZAVZC");
			 System.out.println(s);
		}