code: public void run() {
          while (continueBackup) {
              if (changedListVersion < changedList.getVersion()) {
                  cleanupBackupDir(SAVED_BACKUPS);
                  String filename = String.valueOf(System.currentTimeMillis());
                  File persistFile = new File(backupDir, filename);
                  backingUp = true;
                  changedListVersion = changedList.persist(persistFile);
                  backingUp = false;
              }
  
              sleepAndCheck(backupFrequency);
          }
      }
docs: Runs the backup manager. Writes out files which are a backups of the
  changed list based on the set backup frequency. Retains SAVED_BACKUPS
  number of backup files, removes the rest.