code: protected void createExportBackupFolders(
          File staticExport,
          String exportPath,
          int exportBackups,
          String ruleBackupExtension) {
  
          if (staticExport.exists()) {
              String backupFolderName = exportPath.substring(0, exportPath.lastIndexOf(File.separator) + 1);
              if (ruleBackupExtension != null) {
                  backupFolderName = backupFolderName + EXPORT_BACKUP_FOLDER_NAME + ruleBackupExtension;
              } else {
                  backupFolderName = backupFolderName + EXPORT_BACKUP_FOLDER_NAME;
              }
              for (int i = exportBackups; i > 0; i--) {
                  File staticExportBackupOld = new File(backupFolderName + new Integer(i).toString());
                  if (staticExportBackupOld.exists()) {
                      if ((i + 1) > exportBackups) {
                          // delete folder if it is the last backup folder
                          CmsFileUtil.purgeDirectory(staticExportBackupOld);
                      } else {
                          // set backup folder to the next backup folder name
                          staticExportBackupOld.renameTo(new File(backupFolderName + new Integer(i + 1).toString()));
                      }
                  }
                  // old export folder rename to first backup folder
                  if (i == 1) {
                      staticExport.renameTo(staticExportBackupOld);
                  }
              }
  
              // if no backups will be stored the old export folder has to be deleted
              if (exportBackups == 0) {
                  CmsFileUtil.purgeDirectory(staticExport);
              }
          }
      }
docs: Creates the backup folders for the given export folder and deletes the oldest if the maximum number is reached.<p>
  
  @param staticExport folder for which a new backup folder has to be created
  @param exportPath export path to create backup path out of it
  @param exportBackups number of maximum
  @param ruleBackupExtension extension for rule based backups