code: private void loadClasses(Map infoMap, File file) throws DiffException {
          try {
              JarFile jar = new JarFile(file);
              Enumeration e = jar.entries();
              while (e.hasMoreElements()) {
                  JarEntry entry = (JarEntry) e.nextElement();
                  String name = entry.getName();
                  if (!entry.isDirectory() && name.endsWith(".class")) {
                      ClassReader reader
                          = new ClassReader(jar.getInputStream(entry));
                      ClassInfo ci = loadClassInfo(reader);
                      infoMap.put(ci.getName(), ci);
                  }
              }
          } catch (IOException ioe) {
              throw new DiffException(ioe);
          }
      }
docs: Load all the classes from the specified URL and store information
  about them in the specified map.
  This currently only works for jar files, <b>not</b> directories
  which contain classes in subdirectories or in the current directory.
  
  @param infoMap the map to store the ClassInfo in.
  @param file the jarfile to load classes from.
  @throws IOException if there is an IOException reading info about a
  class.