code: public long loadBackup() {
          long backupTime = -1;
          File[] backupDirFiles = getSortedBackupDirFiles();
          if (backupDirFiles.length > 0) {
              File latestBackup = backupDirFiles[0];
              try {
                  backupTime = Long.parseLong(latestBackup.getName());
                  changedList.restore(latestBackup, this.contentDirs);
              } catch (NumberFormatException e) {
                  logger.error("Unable to load changed list backup. File in " +
                               "changed list backup dir has invalid name: " +
                               latestBackup.getName());
                  backupTime = -1;
              }
          }
          return backupTime;
      }
docs: Attempts to reload the changed list from a backup file. If there are
  no backup files or the backup file cannot be read, returns -1, otherwise
  the backup file is loaded and the time the backup file was written is
  returned.
  
  @return the write time of the backup file, or -1 if no backup is available