code: private String getArchiveFilePath() {
          if ( archiveFileLock == null ) {
              return archiveFilePath;
          } else {
              synchronized( archiveFileLock ) {
                  @SuppressWarnings("unused")
                  File useArchiveFile = getArchiveFile();
                  return archiveFilePath;
              }
          }
      }
docs: Answer the absolute path to the archive file.  Do an extraction if this
  is a nested archive and the file is not yet extracted.  Answer null
  if extraction fails.
  
  @return The absolute path to the archive file.