code: public synchronized InputStream getInputStream(ZipEntry ze)
          throws IOException
      {
          maybeInstantiateVerifier();
          if (jv == null) {
              return super.getInputStream(ze);
          }
          if (!jvInitialized) {
              initializeVerifier();
              jvInitialized = true;
              // could be set to null after a call to
              // initializeVerifier if we have nothing to
              // verify
              if (jv == null)
                  return super.getInputStream(ze);
          }
  
          // wrap a verifier stream around the real stream
          return new JarVerifier.VerifierStream(
              getManifestFromReference(),
              ze instanceof JarFileEntry ?
              (JarEntry) ze : getJarEntry(ze.getName()),
              super.getInputStream(ze),
              jv);
      }
docs: Returns an input stream for reading the contents of the specified
  zip file entry.
  @param ze the zip file entry
  @return an input stream for reading the contents of the specified
  zip file entry
  @throws ZipException if a zip file format error has occurred
  @throws IOException if an I/O error has occurred
  @throws SecurityException if any of the jar file entries
  are incorrectly signed.
  @throws IllegalStateException
  may be thrown if the jar file has been closed