public class Codec {
    private int id = 0;
    private HashMap<Integer, String> map = new HashMap<>();

    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
        String[] strs = longUrl.split("//");
        map.put(id, strs[0] + "/");
        StringBuilder sb = new StringBuilder();
        sb.append(id++);
        String[] body = strs[1].split("/", -1); // -1 means do not discard the last "" string
        for (String s : body) {
            map.put(id, s);
            sb.append(',');
            sb.append(id++);
        }
        return sb.toString();
    }

    // Decodes a shortened URL to its original URL.
    public String decode(String shortUrl) {
        String[] code = shortUrl.split(",");
        LinkedList<String> list = new LinkedList<>();
        for (String c : code) {
            int id = Integer.parseInt(c);
            String s = map.get(id);
            list.add(s);
        }
        String[] strs = list.toArray(new String[list.size()]);
        return String.join("/", strs);
    }
}

// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.decode(codec.encode(url));