below is my code
DocsService client = new DocsService("testappv1");
client.setUserCredentials(username, password);
client.setProtocolVersion(DocsService.Versions.V2);
File file = new File("C:/test.jpg");
DocumentEntry newDocument = new DocumentEntry();
newDocument.setTitle(new PlainTextConstruct("test"));
String mimeType = DocumentListEntry.MediaType.fromFileName(file.getName()).getMimeType();
newDocument.setMediaSource(new MediaFileSource(file, mimeType));
newDocument = client.insert(destFolderUrl, newDocument);
the document was created successful, but it did not contain anything.