code: static Jar create(PathImpl backing)
    {
      if (_jarCache == null) {
        int size = 256;
  
        Integer iSize = _jarSize.get();
  
        if (iSize != null)
          size = iSize.intValue();
        
        _jarCache = new LruCache<PathImpl,Jar>(size);
      }
      
      Jar jar = _jarCache.get(backing);
      
      if (jar != null) {
        jar.updateBacking();
      }
      else if (backing.getScheme().equals("file")) {
        jar = new JarWithFile(backing);
        jar = _jarCache.putIfNew(backing, jar);
      }
      else {
        jar = new JarWithStream(backing);
        jar = _jarCache.putIfNew(backing, jar);
      }
      
      return jar;
    }
docs: Return a Jar for the path.  If the backing already exists, return
  the old jar.