docs: void purge() {
  
          uncommittedCache.clear();
  
          try {
              if (cacheReadonly) {
                  close(false);
              } else {
                  if (dataFile != null) {
                      dataFile.close();
  
                      dataFile = null;
                  }
  
                  FileUtil.getDefaultInstance().delete(fileName);
              }
          } catch (Exception e) {
              throw Error.error(ErrorCode.FILE_IO_ERROR,
                                ErrorCode.M_TextCache_purging_file_error,
                                new Object[] {
                  fileName, e
              });
          }
      }