code: static float getDecompressionRatio(ByteVec bv) {
      long totalSize = 0L;
      long totalCompSize = 0L;
  
      if (bv instanceof FileVec) {
        String strPath = getPathForKey(((FileVec) bv)._key);
  
        try {
          ZipFile zipFile = new ZipFile(strPath);
  
          Enumeration<? extends ZipEntry> entries = zipFile.entries();
  
          while (entries.hasMoreElements()) {
            ZipEntry entry = entries.nextElement();
            if (!entry.isDirectory()) {// add file to list to parse if not a directory.
              totalSize = totalSize + entry.getSize();
              totalCompSize = totalCompSize + entry.getCompressedSize();
            }
          }
          zipFile.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
  
      if (totalCompSize == 0) // something is wrong.  Return no compression.
        return 1;
      else
        return totalSize/totalCompSize;
    }
docs: When a file is a zip file that contains multiple files, this method will return the decompression ratio.
  
  @param bv
  @return