Connecting to Sharepoint from Java

I am trying to connect to SharePoint from my Java code. Below is the code I am using,

 NtlmAuthenticator credentials = new NtlmAuthenticator("DOMAIN", "username", "password");
 // Initialize proxy settings
 HttpProxy httpProxy = new HttpProxy("myProxyServer.com", 8888);
 // Connect to Sharepoint
 SPSite instance = new SPSite(new URL("https://www.server.com/"), credentials, httpProxy, true, SPVersion.SP2013);
// Get root web instance
 SPWeb rootWeb = instance.getRootWeb();
 // Get list of all lists and document libraries from root web
  List<SPList> lists = rootWeb.getLists();

However I am not able to connect. Also i am not getting what to pass for the proxy field.

Can you please help me?