code: public SaveTracksForUserRequest.Builder saveTracksForUser(String... ids) {
      return new SaveTracksForUserRequest.Builder(accessToken)
              .setDefaults(httpManager, scheme, host, port)
              .ids(concat(ids, ','));
    }
docs: Save tracks in the users "Your Music" library.
  
  @param ids The track IDs to add to the users library. Maximum: 50 IDs.
  @return A {@link SaveTracksForUserRequest.Builder}.
  @see <a href="https://developer.spotify.com/web-api/user-guide/#spotify-uris-and-ids">Spotify: URLs &amp; IDs</a>