Can't getPlaylist

[BRKNCD]

Hello, I'm a very noob user, and I'm trying to retrieve a vary specific Playlist from a very specific userId. It seems that I'm not able to do it, the only examples I found are old and don't help me. Here's what I tried:

https://stackoverflow.com/questions/35110025/accessing-list-of-playlists-from-pager-object

SpotifyApi api = new SpotifyApi();
    api.setAccessToken(token);
    SpotifyService spotify = api.getService();
    spotify.getPlaylists("USERID", new Callback<Pager<Playlist>>() {
        @Override
            public void success(Pager<Playlist> playlistPager, Response response) {
                Log.d("TEST", "Got the playlists");
            List<Playlist> playlists = playlistPager.items;
                    for (Playlist p : playlists) {
                        Log.e("TEST", p.name + " - " + p.id);
            }
        }
            @Override
            public void failure(RetrofitError error) {
                Log.e("TEST", "Could not get playlists");
        }
    });

If I copy-paste this, it underlines Callback<Pager> and gives me the error:
Class 'Anonymous Class derived from Callback' must either be declared abstract or implement abstract method 'onResponse(Call, Response) in 'Callback'

if I press alt+enter and add this method and onFailure and I adapt the succes() and failure() methods to those, it will be:

spotify.getPlaylists("USERID", new Callback<Pager<Playlist>>() {
            @Override
            public void onResponse(Call<Pager<Playlist>> playlistPager, Response<Pager<Playlist>> response) {
                Log.d("TEST", "Got the playlists");
                List<Playlist> playlists = playlistPager.items;
                for (Playlist p : playlists) {
                    Log.e("TEST", p.name + " - " + p.id);
                }
            }

            @Override
            public void onFailure(Call<Pager<Playlist>> call, Throwable t) {
                Log.e("TEST", "Could not get playlists");
            }
        });

But now, items is red coloured and it gives me this error: Cannot resolve symbol 'items'
and I can't find any solution to this :(

Thank you, and sorry if it's a silly question