* compacted by dropping redundant lines. A temporary file named "journal.tmp" will be used during
   * compaction; that file should be deleted if it exists when the cache is opened.
   */

  private val journalFile: Path
  private val journalFileTmp: Path
  private val journalFileBackup: Path
  private var size: Long = 0L
  private var journalWriter: BufferedSink? = null