private @NotNull
  StrippedIntOpenHashSet buildPackageHashes() {
    try {
      ZipFile zipFile = getZipFile();
      try {
        Enumeration<? extends ZipEntry> entries = zipFile.entries();
        StrippedIntOpenHashSet result = new StrippedIntOpenHashSet();

        while (entries.hasMoreElements()) {
          ZipEntry entry = entries.nextElement();
          result.add(ClasspathCache.getPackageNameHash(entry.getName()));
        }
        result.add(0); // empty package is in every jar
        return result;
      }
      finally {
        releaseZipFile(zipFile);
      }
    }
    catch (Exception e) {
      error("url: " + myFilePath, e);
      return new StrippedIntOpenHashSet(0);
    }
  }
private @NotNull
  StrippedIntOpenHashSet buildPackageHashes()