sign method
Implementation
String sign(Map<String, String> params) {
SplayTreeMap<String, String> sortedParamMap = SplayTreeMap.from(params);
String canonicalQS = canonicalize(sortedParamMap);
String toSign = REQUEST_METHOD + "\n" + accessString + canonicalQS;
String hmacString = hmac(toSign);
String sig = percentEncodeRfc3986(hmacString);
String url = canonicalQS + "&sig=" + sig;
return url;
}