code: private String rawCreateFolder( CPath path, String parentId )
      {
          JSONObject body = new JSONObject();
          body.put( "title", path.getBaseName() );
          body.put( "mimeType", MIME_TYPE_DIRECTORY );
          JSONArray ids = new JSONArray();
          JSONObject idObj = new JSONObject();
          idObj.put( "id", parentId );
          ids.put( idObj );
          body.put( "parents", ids );
  
          HttpPost request = new HttpPost( FILES_ENDPOINT + "?fields=id" );
          request.setEntity( new JSONEntity( body ) );
  
          RequestInvoker<CResponse> ri = getApiRequestInvoker( request, path );
          JSONObject jresp = retryStrategy.invokeRetry( ri ).asJSONObject();
          return jresp.getString( "id" );
      }
docs: Create a folder without creating any higher level intermediate folders, and returned id of created folder.
  
  @param path
  @param parentId
  @return id of created folder