code: public static DirectoryRosterStore init(final File baseDir) {
          DirectoryRosterStore store = new DirectoryRosterStore(baseDir);
          if (store.setRosterVersion("")) {
              return store;
          }
          else {
              return null;
          }
      }
docs: Creates a new roster store on disk.
  
  @param baseDir
  The directory to create the store in. The directory should
  be empty
  @return A {@link DirectoryRosterStore} instance if successful,
  <code>null</code> else.