How to create a folder in Google Drive, using Java with OAuthRequest

I want to create a new Folder in Google drive, here is my code:

OAuthRequest request = new OAuthRequest(Verb.POST, "https://www.googleapis.com/drive/v2/files");

request.addBodyParameter("title", "Folder");
request.addBodyParameter("mimeType", "application/vnd.google-apps.folder");

service.signRequest(accessToken, request);

Response response = request.send();

I'm getting 401 Unauthorized doing this way. If i take out the addBodyParameter lines, it works, but is created a Untitled file.

I don't know what is wrong, maybe are missing some lines of code, anyone knows how to fix this problem? Thanks in advance.

I've fixed it:

OAuthRequest request = new OAuthRequest(Verb.POST, "https://www.googleapis.com/drive/v2/files");

JSONObject res = new JSONObject();
res.put("title", "Folder");
res.put("mimeType", "application/vnd.google-apps.folder");

request.addPayload(res.toJSONString());
request.addHeader("Content-Length", ""+res.size());
request.addHeader("Content-Type", "application/json");

service.signRequest(accessToken, request);

Response response = request.send();

Had to put the title and the mimeType in a JSONObject, to add it as a Payload to the request, and add to the header of request, the content-lenght and content-type, of the json. Now it's working fine.

I hope it helps someone else later.