public static String decode(String toDecodeContent) {
        if (toDecodeContent == null) {
            return null;
        }
        byte[] buf = null;
        try {
            buf = decoder.decode(toDecodeContent);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return new String(buf);
    }
@param toDecodeContent the String to be decode
@return String after decode
src/main/java/spark/Base64.java